TT Series
Remote Control and Sensor
Transceiver
Data Guide
!
Warning: Linx radio frequency ("RF") products may be
used to control machinery or devices remotely, including machinery
or devices that can cause death, bodily injuries, and/or property
damage if improperly or inadvertently triggered, particularly in industrial
settings or other applications implicating life-safety concerns. No Linx
Technologies product is intended for use in any application without
redundancies where the safety of life or property is at risk.
The customers and users of devices and machinery controlled with
RF products must understand and must use all appropriate safety
procedures in connection with the devices, including without limitation,
using appropriate safety procedures to prevent inadvertent triggering by
the user of the device and using appropriate security codes to prevent
triggering of the remote controlled machine or device by users of other
remote controllers.
Do not use this or any Linx product to trigger an action directly
from the data line or RSSI lines without a protocol or encoder/
decoder to validate the data. Without validation, any signal from
another unrelated transmitter in the environment received by the module
could inadvertently trigger the action.
All RF products are susceptible to RF interference that can prevent
communication. RF products without frequency agility or hopping
implemented are more subject to interference. This module does have
a frequency hopping protocol built in, but the developer should still be
aware of the risk of interference.
Do not use any Linx product over the limits in this data guide.
Excessive voltage or extended operation at the maximum voltage could
cause product failure. Exceeding the reflow temperature profile could
cause product failure which is not immediately evident.
Do not make any physical or electrical modifications to any Linx
product. This will void the warranty and regulatory and UL certifications
and may cause product failure which is not immediately evident.
Table of Contents
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Description
Features
Ordering Information
Electrical Specifications
Absolute Maximum Ratings
Transceiver Timings
TRM-xxx-TT Typical Performance Graphs
Pin Assignments
Pin Descriptions
Theory of Operation
Module Description
Basic Hardware Operation
Transceiver Operation
Transmit Operation
Receive Operation
The Pair Process
Permissions Mask
Acknowledgement
Mode Indicator
Reset to Factory Default
Using the RSSI Line
Using the LATCH_EN Line
Using the Low Power Features
Using the LVL_ADJ Line
Receiver Duty Cycle
Power Supply Requirements
The Command Data Interface
Frequency Hopping
Usage Guidelines for FCC Compliance
32^
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Additional Testing Requirements
Information to the user
Product Labeling
FCC RF Exposure Statement
Antenna Selection
Typical Applications
Antenna Considerations
Helpful Application Notes from Linx
Interference Considerations
Pad Layout
Board Layout Guidelines
Microstrip Details
Production Guidelines
Hand Assembly
Automated Assembly
General Antenna Rules
Common Antenna Styles
Regulatory Considerations
TT Series Remote Control
and Sensor Transceiver
Data Guide
1.150"
(29.21)
Description
The TT Series transceiver is designed for
reliable bi-directional, long-range remote
0.630"
Model: TRM-900-TT
control and sensor applications. It consists of (16.00)
FCC ID: OJMTRM900TTA
IC:
5840A-TRM900TTA
1
a highly optimized Frequency Hopping Spread
Spectrum (FHSS) RF transceiver and integrated
remote control transcoder. The FHSS system 0.131"
(3.33)
allows higher power and, therefore, longer
range than narrowband radios. The transceiver Figure 1: Package Dimensions
has obtained modular approval for the United States and Canada.
Lot FX9nnT
Eight status lines can be set up in any combination of inputs and outputs
for the transfer of button or contact states. A selectable acknowledgement
indicates that the transmission was successfully received. Operating in the
902 to 928MHz frequency band, the module achieves a typical sensitivity of
–112dBm. The base version is capable of generating +12.5dBm transmitter
output power and achieves a range of over 2 miles (3.2 kilometers) line of
site in typical environments with 0dB gain antennas. A high power version
outputs +23.5dBm achieving up to 8 miles (12.8km).
Primary settings are hardware-selectable, which eliminates the need for an
external microcontroller or other digital interface. For advanced features,
optional software configuration is provided by a UART interface; however,
no programming is required for basic operation. Housed in a compact
reflow-compatible SMD package, the transceiver requires no external RF
components except an antenna.
Features
• FCC and Canada pre-certified
• 2 mile (3.2km) or 8 mile (12.8km)
line of sight range
• Highly efficient power use
• Programmable receiver duty cycle
• No programming/tuning required
•
•
•
•
•
– 1 –
8 status lines, 2 byte data input
Bi-directional remote control
Selectable acknowledgements
232 possible addresses
Serial interface for optional
software operation
Revised 3/18/2015
Ordering Information
TT Series Transceiver Specifications
Ordering Information
Parameter
Part Number
Description
RF Section
TRM-900-TT
900MHz TT Series Remote Control and Sensor Transceiver
Operating Frequency Band
TRM-900-TT-A
900MHz Amplified TT Series Remote Control and Sensor Transceiver
Number of Channels
25
EVM-900-TT
900MHz TT Series Evaluation Module
Channel Spacing
500
kHz
EVM-900-TT-A
900MHz Amplified TT Series Evaluation Module
Modulation Rate
45
kbps
EVAL-900-TT
TT Series Basic Evaluation Kit
Receiver Section
EVAL-900-TT-A
Amplified TT Series Basic Evaluation Kit
Spurious Emissions
MDEV-900-TT
TT Series Master Development System
Receiver Sensitivity
MDEV-900-TT-A
Amplified TT Series Master Development System
RSSI Dynamic Range
Symbol
Min.
FC
902
Typ.
Max.
Units
Notes
928
MHz
3
3
3
Per FCC 15.109
–110
–111
dBm
64
dB
5
Transmitter Section
Transceivers are supplied in tubes of 18 pcs.
Output Power
Figure 2: Ordering Information
PO
TRM-xxx-TT
TRM-xxx-TT-A
−15.5
+12.5
dBm
6
TBD
TBD
dBm
6
Output Power Control
Range
Harmonic Emissions
28
dB
PH
Per FCC 15.109
RI N
50
Antenna Port
RF Impedance
Ω
Environmental
Electrical Specifications
TT Series Transceiver Specifications
Parameter
Symbol
Min.
Operating Voltage
VCC
2.5
Peak TX Supply Current
ITX
Typ.
Max.
Units
5.5
VDC
Notes
Power Supply
TT @ +12.5dBm
33.9
38.1
mA
1,2
TT @ 0dBm
15.2
18.9
mA
1,2
TT-A @ +23.5dBm
TBD
mA
1,2
TT-A @ 0dBm
TBD
mA
1,2
Average TX Supply Current
TT @ +12.5dBm
21.3
mA
1,2
TT-A @ +12.5dBm
TBD
mA
1,2
mA
1,2
µA
1,2
µA
1,2
RX Supply Current
IRX
18.8
Standby Current
ISBY
200
Power-Down Current
IPDN
23
0.1
– 2 –
Operating Temp. Range
−40
+85
ºC
Storage Temp. Range
−55
+125
ºC
Timing
Module Turn-On Time
Via VCC
8.0
80
ms
4,13
Via POWER_DOWN
8.0
80
ms
4,13
Via Standby
6.8
ms
4
Serial Command Response
Factory Reset/Erase Table
620
ms
8
Write NV Parameter
16
ms
8
3
ms
8
53
ms
7
Write V/Read/Control
IU to RU Status High
16
Channel Dwell Time
12.3
ms
Interface Section
POWER_DOWN, ACK_EN
Logic Low
VI L
Logic High
VI H
VCC*0.8
– 3 –
VCC*0.2
VDC
VCC
VDC
Transceiver Timings
TT Series Transceiver Specifications
Parameter
Symbol
Min.
Typ.
Max.
Units
Notes
TX Vcc
Input
Logic Low
VI L
0.8
VDC
9
Logic Low
VI L
VCC*0.15
VDC
10
Logic High
VI H
2
5.5
Logic High
VI H
VCC*0.25+0.8
4.5
VDC
10
0.6
VDC
11
VCC
VDC
12
VOL
Logic High
VOH
VCC–0.7
TX Sx
TX MODE_IND
9
Output
Logic Low
VON
RX Sx
RX MODE_IND
A
B
C D E
F
G
H
Certifications
Modular Certifications
1.
2.
3.
4.
5.
6.
7.
8.
Measured at 3.3V VCC
Measured at 25ºC
Guaranteed by design
Characterized but not tested
PER = 5%
Into a 50-ohm load
No RF interference
Response time is from end of
command to start of response
AB – TX Power up Response – <80ms
TT Series Transceiver Timings
FCC, Industry Canada
9. 4.5 ≤ VCC ≤ 5.5
10. VCC ≤ 4.5
11. I ≤ 8mA @ VCC ≥ 5V; I ≤ 6mA @ VCC ≥
3.3V; I ≤ 0.8mA @ VCC ≥ 2.5V
12. I ≤ 3.5mA @ VCC ≥ 5V; I ≤ 3mA @ VCC ≥
3.3V; I ≤ 1mA @ VCC ≥ 2.5V
13. Maximum 80ms if VCC < 2.6V
Figure 3: Electrical Specifications
Absolute Maximum Ratings
Item
Supply Voltage Vcc
−0.3
to
+5.5
VDC
Any Input or Output Pin
−0.3
to
VCC + 0.3
VDC
Operating Temperature
−40
to
+85
ºC
Storage Temperature
−55
to
+125
ºC
RF Input
0
dBm
Minimum
Maximum
8ms
12ms
1ms
4ms
50ms
CD
Data Settle
4µs
8µs
EF
Data Update Delay During Active Session
5ms
25ms
EG
Shutdown Duration
25ms
342ms
GH
RX MODE_IND Drop
6ms
8ms
1.
2.
3.
Absolute Maximum Ratings
Description
BC – RX Initial Response – 8 to 50ms with no interference
1,4
TX Settle
Response
CD – Data
– 4 tofrom
8usVCC or POWER_DOWN
2
AB– Data
TXUpdate
Response
from
Status
line while
IU in–idle
EF
Delay
During
Active
Session
5 to
25ms
EG – Shutdown
Duration
25 to 342ms
TX Response
from– Status
line while IU / RU idle in RX3
GH
MODE_IND
Drop – 6 to 8ms
BC– RXRX
Initial Response
4.
From module off to VCC applied
The module is set as an IU only and is in idle pending status line activation
The module is set as an IU and RU and is idling in receive mode pending status line
activation or receipt of a valid packet.
Maximum 80ms if VCC < 2.6V
Figure 5: TT Series Transceiver Timings
Exceeding any of the limits of this section may lead to permanent damage to the device.
Furthermore, extended operation at these maximum ratings may reduce the life of this
device.
Warning: This product incorporates numerous static-sensitive
components. Always wear an ESD wrist strap and observe proper ESD
handling procedures when working with this device. Failure to observe
this precaution may result in module damage or failure.
Figure 4: Absolute Maximum Ratings
– 4 –
– 5 –
TRM-xxx-TT Typical Performance Graphs
39
Supply Current (mA)
13.00
Output Power (dBm)
8.00
3.00
-2.00
-40°C
85°C
34
29
24
25°C
-7.00
19
-12.00
14
-25
-20
-15
-17.00
0
150
300
450
600
750
900
LVL_ADJ Resistance (kΩ)
-10
-5
0
5
10
15
TX Output Power (dBm)
Figure 8: TT Series Transceiver Peak Current Consumption vs. Transmitter Output Power at 5.5V
Figure 6: TT Series Transceiver Output Power vs. LVL_ADJ Resistance
24
22
34
Supply Current (mA)
Supply Current (mA)
39
85°C
29
24
25°C
-40°C
19
85°C
20
-40°C
25°C
18
16
14
12
14
-25
-20
-15
-10
-5
0
5
TX Output Power (dBm)
Figure 7: TT Series Transceiver Peak Current Consumption vs. Transmitter Output Power at 3.3V
– 6 –
10
15
-25
-20
-15
-10
-5
0
5
10
TX Output Power (dBm)
Figure 9: TT Series Transceiver Average Current Consumption vs. Transmitter Output Power at 3.3V
– 7 –
15
24
16.5
85°C
-40°C
20
85°C
16
25°C
18
16
TX ICC (mA)
Supply Current (mA)
22
25°C
15.5
15
-40°C
14.5
14
14
13.5
13
12
-25
-20
-15
-10
-5
0
5
10
2.5
15
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
5.3
5.5
Supply Voltage (V)
TX Output Power (dBm)
Figure 12: TT Series Transceiver TX Current Consumption vs. Supply Voltage at 0dBm
Figure 10: TT Series Transceiver Average Current Consumption vs. Transmitter Output Power at 5.5V
23
13.5
Transmitter Output Power (dBm)
85°C
22.5
-40°C
22
TX Icc (mA)
2.7
25°C
21.5
21
20.5
20
-40°C
13
25°C
12.5
12
85°C
11.5
11
19.5
2.5
3
3.5
4
4.5
Supply Voltage (V)
Figure 11: TT Series Transceiver TX Current Consumption vs. Supply Voltage at Max Power
– 8 –
5
5.5
2.5
3.3
Supply Voltage (V)
Figure 13: TT Series Transceiver Transmitter Output Power vs. Supply Voltage
– 9 –
5.5
17.5
0.35
85°C
85°C
17
16
-40°C
15.5
15
14.5
Standby Icc (mA)
16.5
RX Icc (mA)
0.3
20°C
25°C
0.25
-40°C
0.2
0.15
14
13.5
2.5
2.8
3.1
3.4
3.7
4
4.3
4.6
4.9
5.2
0.1
5.5
2.5
Supply Voltage (V)
Figure 14: TT Series Transceiver RX Current Consumption vs. Supply Voltage
5.5
Figure 16: TT Series Transceiver Standby Current Consumption vs. Supply Voltage
3.5
10
3.0VDC
3.3VDC
1
5.0VDC
5.5VDC
0.1
0
15
30
45
60
75
90 105 120 135 150 165 180 195 210 225 240 255
Duty Cycle (s)
Figure 15: TT Series Transceiver Average RX Current Consumption vs. Duty Cycle
-40°C
3
2.5VDC
RSSI Output Voltage (V)
Average Current (mA)
3.3
Supply Voltage (V)
85°C
2.5
25°C
2
1.5
1
0.5
0
-111
-101
-91
-81
-71
Figure 17: TT Series Transceiver RSSI Voltage vs. Input Power
– 10 –
-61
RF Input Power Level (dBm)
– 11 –
-51
-41
-31
-21
Pin Assignments
Pin Descriptions Continued
GND
NC
GND
NC
NC
GND
NC
NC
S0
S1
GND
S2
S3
LVL_ADJ
LATCH_EN
RESET
GND
S7
S6
S4
RSSI
GND
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
GND
ANTENNA
GND
NC
NC
GND
NC
NC
ACK_EN
MODE_IND
GND
PAIR
C1
ACK_OUT
C0
CMD_DATA_OUT
GND
CMD_DATA_IN
S5
VCC
POWER_DOWN
GND
Pin Number
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
Name
I/O
15
LATCH_EN
I
If this line is high, then the status line
outputs are latched (a received command
to activate a status line toggles the output
state). If this line is low, then the output lines
are momentary (active for as long as a valid
signal is received).
16
RESET
I
Pull low to perform a soft reset of the
module. This line has an internal pull-up to
POWER_DOWN. May be left unconnected.
21
RSSI
O
Received Signal Strength Indicator. This line
outputs an analog voltage that increases
with the strength of the received signal. It is
updated once a second.
24
POWER_DOWN
I
Power Down. Pulling this line low places the
module into a low-power state. The module
is not functional in this state. Pull high for
normal operation. Do not leave floating.
25
VCC
—
27
CMD_DATA_IN
I
Command Data In. Input line for the serial
interface commands
29
CMD_DATA_OUT
O
Command Data Out. Output line for the
serial interface commands
30
C0
I
This line sets the input/output direction for
status lines S0-S3. When low, the lines are
outputs; when high they are inputs.
31
ACK_OUT
O
This line goes high when the module
receives an acknowledgement message
from another module after sending a control
message.
32
C1
I
This line sets the input/output direction for
status lines S4-S7. When low, the lines are
outputs; when high they are inputs.
Figure 18: TT Series Transceiver Pin Assignments (Top View)
Pin Descriptions
Pin Descriptions
Pin Number
Name
I/O
Description
1, 3, 6, 11,
17, 22, 23,
28, 34, 39,
42, 44
GND
—
Ground
2, 4, 5, 7, 8,
37, 38, 40, 41
NC
—
No Electrical Connection. Do not connect
any traces to these lines.
I/O
Status Lines. Each line can be configured
as either an input to register button or
contact closures or as an output to control
application circuitry.
9, 10, 12, 13,
18, 19, 20, 26
S0 - S7
14
LVL_ADJ 1
I
Level Adjust. This line sets the transmitter
output power level. Pull high or leave open
for the highest power; connect to GND
through a resistor to lower the power.
– 12 –
1.
Description
Supply Voltage
33
PAIR
I
A high on this line initiates the Pair process,
which causes two units to accept each
other’s transmissions. It is also used with
a special sequence to reset the module to
factory default configuration.
35
MODE_IND
O
This line indicates module activity. It can
source enough current to drive a small
LED, causing it to flash. The duration of the
flashes indicates the module’s current state.
36
ACK_EN
I
Pull this line high to enable the module to
send an acknowledgement message after a
valid control message has been received.
43
ANTENNA
—
50-ohm RF Antenna Port
This line has an internal 100kΩ pull-up resistor
Figure 19: TT Series Transceiver Pin Descriptions
– 13 –
Theory of Operation
Module Description
The TT Series transceiver is a low-cost, high-performance synthesized
FSK transceiver. Its exceptional sensitivity results in outstanding range
performance. Figure 20 shows a block diagram for the module.
The TT Series remote control and sensor transceiver module is a
completely integrated RF transceiver and processor. It has two main
modes of operation: hardware and software. Hardware operation is basic
and is suitable for applications like keyfobs where no other processor, PC
or interface is present. Software operation is more advanced and allows for
more features and functionality. This guide focuses on hardware operation
with some references to software operation. Please see Reference Guide
RG-00103: the TT Series Command Data Interface for details on software
operation.
LNA
FSK
DEMOD
LNA
RSSI/
LOGAMP
8-BIT
ADC
ANTENNA
PA
PA RAMP
PROFILE
DIVIDER
LOOP
FILTER
CHARGE
PUMP
PFD
26MHz
OSC
DIVIDER
INTERFACE /
VOLTAGE
TRANSLATION
GPIO /
INTERFACE
LDO
VCC
PDN
fDEV
Σ-Δ
MODULATOR
PROCESSOR
CDR
AFC
AGC
GAUSSIAN
FILTER
Figure 20: TT Series Transceiver RF Section Block Diagram
The TT Series transceiver is designed for operation in the 902 to 928MHz
frequency band. The RF synthesizer contains a VCO and a low-noise
fractional-N PLL. The VCO operates at twice the fundamental frequency
to reduce spurious emissions. The receive and transmit synthesizers
are integrated, enabling them to be automatically configured to achieve
optimum phase noise, modulation quality and settling time.
The transmitter output power is programmable from −15.5dBm to
+12.5dBm with automatic PA ramping to meet transient spurious
specifications. The ramping and frequency deviation are optimized to
deliver the highest performance over a wide range of data rates.
The receiver incorporates highly efficient low-noise amplifiers that provide
up to –112dBm sensitivity. Advanced interference blocking makes the
transceiver extremely robust when in the presence of interference.
A low-power onboard communications processor performs the radio
control and management functions. A control processor performs the
higher level functions and controls the serial and hardware interfaces.
This block also includes voltage translation to allow the internal circuits to
operate at a low voltage to conserve power while enabling the interface to
operate over the full external voltage. This prevents hardware damage and
communication errors due to voltage level differences.
The module has 8 status lines numbered S0 through S7. These can be set
as inputs for buttons or contacts or as outputs to drive application circuitry.
When S0 is taken high on one module S0 goes high on the receiving
module, and so forth. A line that is an input on one side needs to be set as
an output on the other side.
Since this module can act as both transmitter and receiver, terminology and
descriptions are important. This guide uses the term Initiating Unit (IU) to
describe a module that is transmitting commands. Responding Unit (RU) is
used to describe a module that is receiving commands.
The transceiver uses a Frequency Hopping Spread Spectrum (FHSS)
algorithm. This allows for higher output power and longer range than
narrow-band systems while still maintaining regulatory compliance. All
aspects of managing the FHSS operations are automatically handled by the
module.
The TT Series has received modular certification for the FCC in the United
States and Industry Canada when used with an approved antenna. The
module may be placed in an end product without further transmitter
testing, though unintentional radiator testing may be required. Please see
the Usage Guidelines for FCC Compliance section for more details.
While operation is recommended from 3.3V to 5.0V, the transceiver can
operate down to 2.5V.
– 14 –
– 15 –
Basic Hardware Operation
1
GND
The following steps describe how to use the TT Series module with
hardware only. Basic application circuits that correspond to these steps are
shown in Figure 21.
GND
GND
2. Press the PAIR button on both sides. The MODE_IND LED begins
flashing slowly to indicate that the module is searching for another
module.
GND
9
10
11
GND
100k
12
13
VCC
3. Once the pairing is complete, the MODE_IND LED flashes quickly to
indicate that the pairing was successful.
GND
100k
GND
4. The modules are now paired and ready for normal use.
19
20
S4
5. Pressing a status line button on one module (the IU) activates the
corresponding status line output on the second module (the RU).
21
22
GND
S1
MODE_IND
GND
GND
S2
PAIR
C1
ACK_OUT
C0
CMD_DATA_OUT
GND
18
S6
ACK_EN
RESET
17
S7
NC
S0
LATCH_EN
16
GND
NC
LVL_ADJ
15
GND
NC
S3
14
91k 1%
GND
NC
8
VCC
NC
GND
7
100k
NC
NC
6
VCC
GND
NC
5
100k
ANTENNA
GND
4
VCC
GND
NC
3
GND
GND
1. Set the C0 and C1 lines opposite on both sides.
GND
2
GND
S7
CMD_DATA_IN
S6
S5
S4
VCC
RSSI
POWER_DOWN
GND
GND
44
GND
43
42
GND
41
40
39
GND
38
37
36
VCC
35
34
GND
GND
VCC
33
32
100k
GND
GND
31
30
GND
VCC
29
28
27
GND
VCC
26
25
24
23
S5
VCC
VCC
GND
TRM-XXX-TT
6. Taking the ACK_EN
line high
on the RU causes
the
module to send an
GND
GND
GND
GND
2
43
acknowledgement to the
IU. The ACK_OUT
NC
ANTENNA line on the IU goes high to
3
42
GND
GND
GND
GND
indicate that the acknowledgement
has been
received.
Tying the line
4
41
NC
VCC
NC
to Vcc causes the module
to
send
an
acknowledgement
as soon as a
5
40
NC
GND
NC
100k
command message
is received.
6
39
GND
GND
GND
GND
1
7
VCC
44
NC
NC
GND
2
GND
13
S3
C1
5
GND
32
S7
18
GND
8
S0
S1
GND
S2
GND
S3
31
S7
CMD_DATA_IN
27
VCC
19
26
The Command Data Interface
section describes
advanced
S6
S5 the more
S6
S5
25
20
VCC
S4
S4
VCC
features that are available with the serial interface.
21
GND
22
RSSI
POWER_DOWN
GND
GND
24
23
6
7
38
GND
GND
GND
LVL_ADJ
ACK_OUT
Sensor
applications
can replace
the buttons
with triggered outputs from
100k
91k 1%
15
30
GND
LATCH_EN
C0
VCC
sensors. A comparator circuit
can be used to trigger
a line when a sensor
16
29
RESET
CMD_DATA_OUT
reading crosses a threshold,
17 providing a warning or
28 indication to a user.
GND
GND
GND
GND
14
3
4
8
37
GND is suitable for basic remote
NC control or command
NC
This
systems. No
100k
9
36
VCC
ACK_EN
programming is necessary forS0basic hardware
operation.
The following
10
35
S1
VCC
GND
MODE_IND
sections describe the functions
in more detail and34the Typical Applications
11
GND
GND
GND
GND
GND
VCC
section100kshows additional example
schematicsPAIR
for 33using the100kmodules.
12
S2
VCC
1
GND
9
10
11
12
13
14
91k 1%
VCC
15
16
GND
18
VCC
GND
VCC
VCC
GND
GND
TRM-XXX-TT
17
19
100k
20
21
100k
GND
22
GND
GND
NC
ANTENNA
GND
GND
NC
NC
NC
NC
GND
GND
NC
NC
NC
NC
S0
ACK_EN
S1
MODE_IND
GND
GND
S2
PAIR
S3
C1
LVL_ADJ
ACK_OUT
LATCH_EN
RESET
C0
CMD_DATA_OUT
GND
S7
GND
CMD_DATA_IN
S6
S5
S4
VCC
RSSI
POWER_DOWN
GND
GND
44
GND
43
42
GND
41
40
39
GND
38
37
36
VCC
35
34
GND
GND
33
32
100k
VCC
31
30
GND
29
28
27
GND
VCC
26
25
24
23
VCC
VCC
100k
VCC
GND
TRM-XXX-TT
100k
Figure 21: TT Series Transceiver Basic Application Circuits for Bi-directional Remote Control
– 16 –
– 17 –
GND
GND
VCC
GND
VCC
GND
Transceiver Operation
Transmit Operation
The transceiver has two modes of operation: Initiating Unit (IU) that
transmits control messages and Responding Unit (RU) that receives control
messages. If all of the status lines are set as inputs, then the module is set
as an IU only. The module stays in a low power sleep mode until a status
line goes high, starting the Transmit Operation.
Transmit Operation is entered when any of the status line inputs go high.
During Transmit Operation, the MODE_IND line is high. The module
repeatedly transmits control messages containing the local address and
the state of all status lines. Between transmissions the module listens for
acknowledgement messages. If an Acknowledge (ACK) or Acknowledge
with Data (AWD) message is received for the transmitted data, the
ACK_OUT line is asserted for 100ms. The ACK_OUT timing restarts on
each ACK or AWD packet that is received.
If all of the status lines are set as outputs, then the module is set as an RU
only. It stays in Receive Operation looking for a valid transmission from a
paired IU.
A module with both input and output status lines can operate as an IU
and an RU. The module idles in Receive Operation until either a valid
transmission is received or a status line input goes high, initiating the
Transmit operation.
When an input goes high, the transceiver captures the logic state of each
of the status lines. The line states are placed into a packet along with the
local 32-bit address. The IU transmits the packets as it hops among 25 RF
channels.
An RU receives the packet and checks its Paired Module List to see if the
IU has been paired with the module and is authorized to control it. If the
IU’s address is not in the table, then the RU ignores the transmission. If
the address is in the table, then the RU calculates the channel hopping
pattern from the IU’s address and sets its status line outputs according to
the received packet. It then hops along with the IU and updates the states
of its outputs with every packet. Its outputs can be connected to external
circuitry that activates when the lines go high.
The RU can also send an acknowledgement back to the IU. Using the
serial interface the RU can include up to two bytes of custom data with
the acknowledgement, such as sensor data or battery voltage levels.
Using the hardware control, if ACK_EN is high when a valid control packet
is received, the module sends back a simple acknowledgement (ACK). It
sends an Acknowledge with Data (AWD) response when custom data is
programmed into the module using a serial command.
The transceiver sends control messages every 12.5ms as long as any
of the status line inputs is high, updating the status line states with
each packet. When all input lines are low, the module starts the shutoff
sequence.
During the shutoff sequence, the transmitter sends at least one packet with
all outputs off. It then continues to transmit data until the current channel
hopping cycle is complete, resulting in balanced channel use. If an input
line is asserted during the shutoff sequence, the transmitter cancels the
shutoff and extends the transmission sequence.
Receive Operation
During Receive Operation, the module waits for a valid control message
from an authorized (paired) transceiver. When a valid message is received,
it locks onto the hopping pattern of the transmitter and asserts the MODE_
IND line. It compares the received status line states to the Permission Mask
for the IU to see if the IU is authorized to activate the lines. The module sets
all authorized outputs to match the received states.
Only status line outputs are affected by received control packets. Received
commands to change an input line have no effect.
The RU then checks the state of the ACK_EN line and transmits an
acknowledgement packet if it is high. It looks for the next valid packet while
maintaining the frequency hopping timing. As long as an RU is receiving
valid commands from a paired IU, it will not respond to any other unit.
Once eight consecutive packets are missed, the RU is logically
disconnected from the IU and waits for the next valid packet from any IU.
– 18 –
– 19 –
The Pair Process
Permissions Mask
The Pair process enables two transceivers to communicate with each
other. Each transceiver has a local 32-bit address that is transmitted with
every packet. If the address in the received packet is not in the RU’s Paired
Module List, then the transceiver does not respond. Adding devices to
the authorized list is accomplished through the Pair process or by a serial
command. Each module can be paired with up to 40 other modules.
The TT Series Transceiver has a Permissions Mask that is used to
control which lines an IU is authorized to control. With most systems, if
a transmitter is associated with a receiver then it has full control over the
receiver. With the Permissions Mask, a transmitter can be granted authority
to control only certain receiver outputs. If an IU does not have the authority
to activate a certain line, then the RU does not set it.
The Pair process is initiated by taking the PAIR line high on both units
to be associated. Activation can either be a momentary pulse (less than
two seconds) or a sustained high input, which can be used to extend the
search and successful pairing display. With a momentary activation, the
search is terminated after 30 seconds. If Pairing is started with a sustained
high input, the search continues as long as the PAIR input is high.
As an example, a factory worker can be given a fob that only opens the
door to the factory floor while the CEO has a fob that can also open
the executive offices. The hardware in the fobs is the same, but the
permissions masks are set differently for each fob.
When Pair is activated, the module displays the Pair Search sequence
on the MODE_IND line (Figure 22) and goes into a search mode where it
looks for another module that is also in search mode. It alternates between
transmit and receive, enabling one unit to find the other and respond.
Once bidirectional communication is established, the two units store each
other’s addresses in their Paired Module List with full Permissions Mask
and display the Pair Found sequence on their MODE_IND lines. The Pair
Found sequence is displayed for at least 3 seconds. If the PAIR input is
held high from the beginning of Pairing, the Pair Found display is shown for
as long as PAIR is high.
When Pairing is initiated, the module pairs with the first unit it finds that is
also in Pair Search. If multiple systems are being Paired in the same area,
such as in a production environment, then steps should be taken to ensure
that the correct units are paired with each other.
The Pair process can be canceled by taking PAIR high a second time.
If the address table is full when the PAIR line is raised, the Pair Error
sequence is displayed on the MODE_IND line for 10 seconds and neither
of the Pairing units will store an address. In this case, the module should
either be reset to clear the address table or the serial interface can be used
to remove addresses.
The Pair process always sets the Permission Mask to full access. The mask
can be changed through the serial interface.
Acknowledgement
A responding module is able to send an acknowledgement to the
transmitting module. This allows the initiating module to know that the
responding side received the command.
When the Responding Unit (RU) receives a valid Control Packet, it
checks the state of the ACK_EN line. If it is high the module sends an
Acknowledgement Packet.
If the Initiating Unit (IU) receives an Acknowledgement Packet that has
the same Address and Status Byte as in the Control Packet it originally
sent, then it pulls the ACK_OUT line high. A continuous stream of Control
Packets that triggers a continuous stream of Acknowledgement Packets
keeps the ACK_OUT line high.
Connecting the ACK_EN line to VCC causes the RU to transmit
Acknowledgement Packets as soon as it receives a valid Control Packet.
Alternately this line can be controlled by an external circuit that raises the
line when a specific action has taken place. This confirms to the IU that the
action took place and not just acknowledges receipt of the signal.
If a paired unit is already in the Paired Module List, then no additional entry
is added though the existing entry’s Permissions Mask may be modified.
– 20 –
– 21 –
Mode Indicator
Using the RSSI Line
The Mode Indicator line (MODE_IND) provides feedback about the current
state of the module. This line switches at different rates depending on the
module’s current operation. When an LED is connected to this line it blinks,
providing a visual indication to the user. Figure 22 gives the definitions of
the MODE_IND timings.
The module’s Received Signal Strength Indicator (RSSI) line outputs a
voltage proportional to the incoming signal strength. The RSSI Voltage vs.
Input Power graph in the Typical Performance Graphs section shows the
relationship between the RSSI voltage and the incoming signal power. This
line has a high impedance so an external buffer may be required for some
applications.
MODE_IND Timing
Module Status
Display
Transmit Mode
Solid ON when transmitting packets.
Receive Mode
Solid ON when receiving packets.
Pair Search
ON for 100ms, OFF for 900ms while searching for another unit
during the Pair process
Pair Found
ON for 400ms, OFF for 100ms when the transceiver has been
Paired with another transceiver. This is displayed for at least 3
seconds.
Pair Error
ON for 100ms, OFF for 100ms when the address table is full and
another unit cannot be added.
Remote Pair Error
ON for 100ms, OFF for 100ms, ON for 100ms OFF for 300ms
when the remote unit’s address table is full and a Pair cannot be
completed.
Pair Canceled
ON for 100ms, OFF for 200ms, ON for 100ms when the Pair
process is canceled.
Reset
Acknowledgement
ON for 600ms, OFF for 100ms, ON for 200ms, OFF for 100ms,
ON for 200ms and OFF for 100ms when the reset sequence is
recognized.
Extended Pair
Completed
Solid ON when the pairing operation is completed and waiting for
the PAIR line to go low.
The RSSI line updates once a second showing either the strength
of the packet received within the last second or the current channel
measurement. The formula to convert the RSSI voltage to power in dBm is:
PRX = (VRSSI / VCC) * 60 – 105
Note: The RSSI levels and dynamic range vary from part to part. It is also
important to remember that the RSSI output indicates the strength of
any in-band RF energy and not necessarily just that from the intended
transmitter; therefore, it should be used only to qualify the presence and
level of a signal. Using RSSI to determine distance or data validity is not
recommended.
The RSSI output can be utilized during testing or even as a product feature
to assess interference and channel quality by looking at the RSSI level with
all intended transmitters shut off.
Using the LATCH_EN Line
Figure 22: MODE_IND Timing
Reset to Factory Default
The transceiver is reset to factory default by taking the Pair line high briefly
4 times, then holding Pair high for more than 3 seconds. Each brief interval
must be high 0.1 to 2 seconds and low 0.1 to 2 seconds. (1 second
nominal high / low cycle). The sequence helps prevent accidental resets.
Once the sequence is recognized the MODE_IND line blinks the Reset
Acknowledgement defined in Figure 22 until the PAIR line goes low. After
the input goes low, the configuration is initialized. Factory reset also clears
the Paired Module table but does not change the local address.
The LATCH_EN line sets the outputs to either momentary operation or
latched operation. During momentary operation the outputs go high for as
long as control messages are received instructing the module to take the
lines high. As soon as the control messages stop, the outputs go low.
During latched operation, when a signal is received to make a particular
status line high, it will remain high until a separate activation is received to
make it go low. The transmission must stop and the module must time out
before it will register a second transmission and toggle the outputs.
When the LATCH_EN line is high, all of the outputs are latched. A serial
command is available to configure latching of individual lines.
If the PAIR input timing doesn’t match the reset sequence timing, the
module reverts to normal operation without a reset or pairing.
– 22 –
– 23 –
Using the Low Power Features
The Power Down (POWER_DOWN) line can be used to completely power
down the transceiver module without the need for an external switch.
This line allows easy control of the transceiver power state from external
components, such as a microcontroller. The module is not functional while
in power down mode.
Warning: Pulling any of the module inputs high while in Power Down
can partially activate the module, increasing current consumption
and potentially placing it into an indeterminate state that could lead
to unpredictable operation. Pull all inputs low before pulling POWER_
DOWN low to prevent this issue. Lines that may be hardwired (for
example, the ACK_EN line) can be connected to the POWER_DOWN
line so that they are lowered when POWER_DOWN is lowered.
Power Level vs. Resistor Value
Power
Level
PO
(dBm)
1%
Resistor
Value
Power
Level
PO
(dBm)
1%
Resistor
Value
Power
Level
PO
(dBm)
1%
Resistor
value
57
12.2
Open
38
3.4
154k
19
−5.4
44.2k
56
12.1
750k
37
3.1
143k
18
−5.7
41.2k
55
12.1
649k
36
2.7
133k
17
−6.1
37.4k
54
11.8
576k
35
2.1
127k
16
−6.7
34.8k
53
11.8
510k
34
1.6
118k
15
−7.0
32.4k
52
9.5
453k
33
1.1
111k
14
−7.5
29.4k
51
9.7
412k
32
0.8
105k
13
−7.9
26.7k
50
8.9
347k
31
0.3
97.6k
12
−8.3
24.3k
49
8.3
340k
30
−0.1
91k
11
−8.8
22k
48
8.0
316k
29
−0.6
86.6k
10
−9.3
19.6k
Using the LVL_ADJ Line
47
7.4
287k
28
−0.9
80.6k
9
−9.1
17.4k
The Level Adjust (LVL_ADJ) line allows the transceiver’s output power to be
easily adjusted for range control or lower power consumption. This is done
by placing a resistor to ground on LVL_ADJ to form a voltage divider with
an internal 100kΩ resistor. When the transceiver powers up, the voltage on
this line is measured and the output power level is set accordingly. When
LVL_ADJ is connected to VCC or floating, the output power and current
consumption are the highest. When connected to ground, the output
power and current are the lowest. The power is digitally controlled in 58
steps providing approximately 0.5dB per step. See the Typical Performance
Graphs section (Figure 6) for a graph of the output power vs. LVL_ADJ
resistance.
46
6.9
267k
27
−1.4
76.8k
8
−9.6
15.4k
45
6.7
243k
26
−1.8
71.5k
7
−10.2
13.3k
44
6.3
226k
25
−2.3
66.5k
6
−10.8
11.3k
43
5.8
210k
24
−2.8
62k
5
−11.5
9.53k
42
5.3
200k
23
−3.2
57.6k
4
−12.2
7.5k
41
4.8
182k
22
−3.7
54.9k
3
−13.0
5.76k
40
4.3
174k
21
−4.3
51k
2
−13.9
4.02k
39
4.0
165k
20
−4.8
47k
1
−14.5
2.32k
0
−15.7
750
Figure 23: Power Level vs. Resistor Value
Warning: The LVL_ADJ line uses a resistor divider to create a voltage
that determines the output power. Any additional current sourcing or
sinking can change this voltage and result in a different power level. The
power level should be checked to confirm that it is set as expected.
Even in designs where attenuation is not anticipated, it is a good idea to
place resistor pads connected to LVL_ADJ and ground so that it can be
used if needed. Figure 23 shows the 1% tolerance resistor value that is
needed to set each power level and gives the approximate output power
for each level. The output power levels are approximate and may vary
part-to-part.
– 24 –
– 25 –
The module can be configured to automatically power on and off while
in receive mode. Instead of being powered on all the time looking for
transmissions from an IU, the receiver can wake up, look for data and go
back to sleep for a configurable amount of time. If it wakes up and receives
valid data, then it stays on and goes back to sleep when the data stops.
This significantly reduces the amount of current consumed by the receiver.
It also increases the time from activating the IU to getting a response from
the RU.
The duty cycle is controlled by the Duty Cycle serial command through the
Command Data Interface. DCycle sets the number of seconds between
receiver turn on points as shown in Figure 24.
DCycle
TON
TSBY
KeepOn
Activity
ON
Standby
Figure 24: Receiver Duty Cycle
The module’s average current consumption can be calculated with the
following equation.
IAVG =
(TON × IRX ) + (TSBY × ISBY )
DCycle
Figure 25: Receiver Duty Cycle Average Current Consumption Equation
TON is fixed at about 0.326 seconds and TSBY = DCycle - TON. The receiver
current (IRX) and standby current (ISBY) vary with supply voltage, but some
typical values are in Figure 26.
consumption can be significantly reduced with even a small duty cycle
value. This is ideal for battery-powered applications that need infrequent
updates or where response time is not critical.
The KeepOn time is used to keep the receiver on after it has completed
some activity. This activity includes completing a transmission and receiving
a valid packet. After KeepOn seconds have elapsed with no transmit or
valid receive activity, the module goes into standby for DCycle seconds.
Please see Reference Guide RG-00103: the TT Series Command Data
Interface for details on configuring the receiver duty cycle.
Power Supply Requirements
The transceiver incorporates a precision
low-dropout regulator which allows operation
over a wide input voltage range. Despite this
regulator, it is still important to provide a supply
that is free of noise. Power supply noise can
significantly affect the module’s performance, so
providing a clean power supply for the module
should be a high priority during design.
2.5
3.0
3.3
3.5
4.0
4.5
5.0
5.5
IRX
(mA)
16.5
17.8
18.7
18.8
18.8
18.9
18.9
18.9
ISBY
(mA)
0.0862
0.1471
0.1509
0.1525
0.1569
0.1616
0.1669
0.1737
Figure 26: TT Series Transceiver Typical Current Consumption
Figure 15 shows a graph of the average current consumption vs. duty cycle
for several supply voltages. This graph shows that the average current
– 26 –
10Ω
Vcc IN
10µF
Figure 27: Supply Filter
A 10Ω resistor in series with the supply followed by a 10μF tantalum
capacitor from Vcc to ground helps in cases where the quality of supply
power is poor (Figure 27). This filter should be placed close to the module’s
supply lines. These values may need to be adjusted depending on the
noise present on the supply line.
TT Series Typical Current Consumption
VCC
(VDC)
Vcc TO
MODULE
+
Receiver Duty Cycle
– 27 –
The Command Data Interface
The TT Series transceiver has a serial Command Data Interface (CDI)
that offers the option to configure and control the transceiver through
software instead of through hardware. This interface consists of a standard
UART with a serial command set. This allows for fewer connections in
applications controlled by a microcontroller as well as for more control and
advanced features than can be offered through hardware pins alone.
The serial port uses the CMD_DATA_IN and CMD_DATA_OUT lines as a
UART. An automatic baud rate detection system allows the interface to run
at a variable data rate from 9.6kbps to 57.6kbps.
The Command Data Interface has two sets of operators. One is a set
of commands that performs specific tasks and the other is a set of
parameters that are for module configuration and status reporting. These
are shown in Figure 28.
TT Series Transceiver Command Data Interface Reference Guide has full
details on each command. Some key features available with the serial
interface are:
•
•
Configure the module through software instead of setting the hardware
lines.
Change the output power, providing the ability to lower power
consumption when signal levels are good and extend battery life.
•
Individually set which status lines are inputs and outputs.
•
Individually set status line outputs to operate as momentary or latched.
•
Add or remove specific paired devices.
•
Individually set Permission Masks that prevent certain paired devices
from activating certain status line outputs.
•
Change the module’s local address for production or tracking purposes
or to replace a lost or broken product.
•
Put the module into a low power state to conserve battery power.
– 28 –
•
Receive the entire control message serially instead of needing to
monitor individual status lines. Get the IU address for logging access
attempts.
•
Receive control messages from unpaired modules, allowing for
expansion of the system beyond the maximum of 40 paired units.
Access control and address validation can be undertaken by an
external processor or PC with more memory than the module.
•
Serially configure and control acknowledge messages.
•
Send and receive 2 bytes (16 bits) of custom data with each command
message and acknowledge message.
•
Serially initiate transmission of control messages instead of triggering
the status line inputs.
•
Set interrupts to notify an external processor when specific events
occur, such as receiving a control message.
•
Read out the RSSI value for the last received packet and the current
ambient RF level.
•
Set the receiver duty cycle for automatically powering on and off to
save battery power.
The serial interface offers a great deal of flexibility for use more complicated
designs. Please see Reference Guide RG-00103: the TT Series Command
Data Interface for details on the CDI. A list of the serial commands is shown
in Figure 28 for reference.
– 29 –
Command Data Interface Commands and Parameters
Command
Description
Read
Read the current value in volatile memory. If there is no volatile
value, then the non-volatile value is returned.
Write
Write a new value to volatile memory.
Read NV
Read the value in non-volatile memory.
Program
Program a new value to non-volatile memory.
Set Default
Configuration
Set all configuration items to their factory default values.
Erase All Addresses
Erase all paired addresses from memory.
Transmit Control Data
Transmit ACK
Frequency Hopping
The module incorporates a Frequency Hopping Spread Spectrum (FHSS)
algorithm. This provides immunity from narrow-band interference as well as
meets regulatory requirements for higher output power, resulting in longer
range.
The module uses 25 RF channels as shown in Figure 29.
Channel Frequencies
Channel
Number
Frequency
Channel
Number
Frequency
Channel
Number
Frequency
Transmit a control message.
1
902.62
10
907.12
18
911.12
Transmit an acknowledgement for received data.
2
903.12
11
907.62
19
911.62
Transmit AWD
Transmit an Acknowledge With Data (AWD) response with two
bytes of custom data.
3
903.62
12
908.12
20
912.12
Parameter
Description
4
904.12
13
908.62
21
912.62
904.62
14
909.12
22
913.12
Device Name
NULL-terminated string of up to 16 characters that identifies the
module. Read only.
5
6
905.12
15
909.62
23
913.62
905.62
16
910.12
24
914.12
17
910.62
25
914.62
Firmware Version
3 byte firmware version. Read only.
7
Serial Number
4 byte factory-set serial number. Read only.
8
906.12
Local Address
The module’s 32-bit local address.
9
906.62
Status Line I/O Mask
Status lines direction (1 = Inputs, 0 = Outputs), LSB = S0, used
when enabled by Control Source
Latch Mask
Latching enable for output lines, LSB = S0, used when enabled
by Control Source
TX Power Level
TX output power, signed nominal dBm, used when enabled by
Control Source
Control Source
Configures the control options.
Message Select
Select message types to capture for serial readout.
Paired Module
Descriptor
Sets the index number, address and permissions mask of paired
modules.
Duty Cycle
Receiver duty cycle control
I/O Lines
Read the current state of the status and control lines.
RSSI
Read the RSSI of the last packet received and ambient level.
Read only.
LADJ
Read the voltage on the LVL_ADJ line. Read only.
Module Status
Read the operating status of the module.
Captured Receive
Packet
Read the last received packet. Read only.
Interrupt Mask
Sets the mask for events to generate a break on CMD_DATA_
OUT.
Event Flags
Event flags that are used with the Interrupt Mask.
Figure 29: TT Series Transceiver RF Channel Frequencies
Each channel has a time slot of 12.5ms before the module hops to the next
channel. This equal spacing allows a receiver to hop to the next channel
at the correct time even if a packet is missed. Up to seven consecutive
packets can be missed without losing synchronization.
The hopping pattern is determined from the transmitter’s address. Each
sequence uses all 25 channels, but in different orders. Once a transmission
starts, the module continues through a complete cycle. If the input line
is taken low in the middle of a cycle, the module continues transmitting
through the end of the cycle to ensure balanced use of all channels.
Frequency hopping has several advantages over single channel operation.
Hopping systems are allowed a higher transmitter output power, which
results in longer range and better performance within that range. Since
the transmission is moving among multiple channels, interference on one
channel causes loss on that channel but does not corrupt the entire link.
This improves the reliability of the system.
Figure 28: TT Series Transceiver Command Data Interface Commands and Parameters
– 30 –
– 31 –
Usage Guidelines for FCC Compliance
Information to the user
The TT Series module is provided with an FCC and Industry Canada
Modular Certification. This certification shows that the module meets the
requirements of FCC Part 15 and Industry Canada license-exempt RSS
standards for an intentional radiator. The integrator does not need to
conduct any further testing under these rules provided that the following
guidelines are met:
The following information must be included in the product’s user manual.
•
An approved antenna must be directly coupled to the module’s U.FL
connector through an approved coaxial extension cable.
•
Alternate antennas can be used, but may require the integrator to
perform certification testing.
•
The module must not be modified in any way. Coupling of external
circuitry must not bypass the provided connectors.
•
End product must be externally labeled with “Contains FCC ID:
OJMTRM900TTA / IC: 5840A-TRM900TTA”.
•
The end product’s user’s manual must contain an FCC statement
equivalent to that listed on page 33 of this data guide.
•
The antenna used for this transceiver must not be co-located or
operating in conjunction with any other antenna or transmitter.
•
The integrator must not provide any information to the end-user on
how to install or remove the module from the end-product.
Note: The integrator is required to perform unintentional radiator testing
on the final product per FCC sections 15.107 and 15.109 and IC
RSS-GEN.
Any changes or modifications not expressly approved by Linx Technologies
could void the user’s authority to operate the equipment.
Additional Testing Requirements
The modules have been tested for compliance as an intentional radiator,
but the integrator is required to perform unintentional radiator testing
on the final product per FCC sections 15.107 and 15.109 and Industry
Canada license-exempt RSS standards. Additional product-specific testing
might be required. Please contact the FCC or Industry Canada regarding
regulatory requirements for the application. Ultimately is it the integrator’s
responsibility to show that their product complies with the regulations
applicable to their product.
– 32 –
FCC / IC NOTICES
This product contains FCC ID: OJMTRM900TTA / IC: 5840A-TRM900TTA
This device complies with Part 15 of the FCC rules and Industry Canada
license-exempt RSS standards. Operation of this device is subject to the
following two conditions:
1. This device may not cause harmful interference, and
2. this device must accept any interference received, including interference that
may cause undesired operation.
This equipment has been tested and found to comply with the limits for a Class
B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed
to provide reasonable protection against harmful interference in a residential
installation. This equipment generates, uses and can radiate radio frequency
energy and, if not installed and used in accordance with the instructions,
may cause harmful interference to radio communications. However, there is
no guarantee that interference will not occur in a particular installation. If this
equipment does cause harmful interference to radio or television reception, which
can be determined by turning the equipment off and on, the user is encouraged
to try to correct the interference by one or more of the following measures:
•
•
•
•
Reorient or relocate the receiving antenna.
Increase the separation between the equipment and receiver.
Connect the equipment into an outlet on a circuit different from that to which
the receiver is connected.
Consult the dealer or an experienced radio/TV technician for help.
Any modifications could void the user’s authority to operate the equipment.
Le présent appareil est conforme aux CNR d’Industrie Canada applicables
aux appareils radio exempts de licence. L’exploitation est autorisée aux deux
conditions suivantes:
1. l’appareil ne doit pas produire de brouillage, et
2. ’utilisateur de l’appareil doit accepter tout brouillage radioélectrique subi,
même si le brouillage est susceptible d’en compromettre le fonctionnement.
– 33 –
Product Labeling
The end product must be labeled to meet the FCC and IC product label
requirements. It must have the below or similar text:
Contains FCC ID: OJMTRM900TTA / IC: 5840A-TRM900TTA
The label must be permanently affixed to the product and readily visible to
the user. ‘‘Permanently affixed’’ means that the label is etched, engraved,
stamped, silkscreened, indelibly printed, or otherwise permanently marked
on a permanently attached part of the equipment or on a nameplate of
metal, plastic, or other material fastened to the equipment by welding,
riveting, or a permanent adhesive. The label must be designed to last
the expected lifetime of the equipment in the environment in which the
equipment may be operated and must not be readily detachable.
FCC RF Exposure Statement
To satisfy RF exposure requirements, this device and its antenna must
operate with a separation distance of at least 20cm from all persons and
must not be co-located or operating in conjunction with any other antenna
or transmitter.
Antenna Selection
Under FCC and Industry Canada regulations, this radio transmitter may
only operate using an antenna of a type and maximum (or lesser) gain
approved for the transmitter by the FCC and Industry Canada. To reduce
potential radio interference to other users, the antenna type and its gain
should be so chosen that the equivalent isotropically radiated power
(e.i.r.p.) is not more than that necessary for successful communication.
The TRM-900-TT radio transmitter has been approved by the FCC and
Industry Canada to operate with the antenna types listed in Figure 30 with
the maximum permissible gain and required antenna impedance for each
antenna type indicated. Antenna types not included in this list, having a
gain greater than the maximum gain indicated for that type, are strictly
prohibited for use with this device.
Conformément à la réglementation d’Industrie Canada, le présent émetteur
radio peut fonctionner avec une antenne d’un type et d’un gain maximal
(ou inférieur) approuvé pour l’émetteur par Industrie Canada. Dans le but
de réduire les risques de brouillage radioélectrique à l’intention des autres
utilisateurs, il faut choisir le type d’antenne et son gain de sorte que la
puissance isotrope rayonnée équivalente (p.i.r.e.) ne dépasse pas l’intensité
nécessaire à l’établissement d’une communication satisfaisante.
– 34 –
Le présent émetteur radio (TRM-900-TT) a été approuvé par Industrie
Canada pour fonctionner avec les types d’antenne énumérés la Figure 30
et ayant un gain admissible maximal et l’impédance requise pour chaque
type d’antenne. Les types d’antenne non inclus dans cette liste, ou dont le
gain est supérieur au gain maximal indiqué, sont strictement interdits pour
l’exploitation de l’émetteur.
Antennas / Antennes
Linx Part Number
Référence Linx
Type
Gain
Impedance
Impédance
Tested Antennas
ANT-916-CW-QW
¼ Wave Whip
1.84dBi
50Ω
ANT-916-CW-HW
½ Wave Dipole Helical
1.83dBi
50Ω
ANT-916-PW-LP
¼ Wave Whip
2.44dBi
50Ω
ANT-916-SP
¼ Wave Planar
1.35dBi
50Ω
ANT-916-WRT-RPS
½ Wave Dipole Helical
1.83dBi
50Ω
ANT-916-CHP
¼ Wave Ceramic
1.34dBi
50Ω
Antennas of the same type and same or lesser gain
ANT-916-CW-HD
¼ Wave Whip
–0.26dBi
50Ω
ANT-916-PW-QW
¼ Wave Whip
1.84dBi
50Ω
ANT-916-CW-RCL
¼ Wave Whip
–2.03dBi
50Ω
ANT-916-CW-RH
¼ Wave Whip
–1.31dBi
50Ω
ANT-916-CW-HWR-RPS
½ Wave Dipole Helical
–1.89dBi
50Ω
ANT-916-PML
½ Wave Dipole Helical
–0.38dBi
50Ω
ANT-916-PW-RA
¼ Wave Whip
0dBi
50Ω
ANT-916-USP
¼ Wave Planar
0.3dBi
50Ω
Cable Assemblies / Assemblages de Câbles
Linx Part Number
Référence Linx
Description
CSI-RSFB-300-UFFR*
RP-SMA Bulkhead to U.FL with 300mm cable
CSI-RSFE-300-UFFR*
RP-SMA External Mount Bulkhead to U.FL with 300mm cable
* Also available in 100mm and 200mm cable length
Figure 30: TT Series Approved Antennas
– 35 –
Typical Applications
GND
1
GND
GND
44
GND
GND
NC
Figure 31 and Figure 32 show circuits
usingANTENNA
the TT Series transceiver.
2
GND
GND
VCC
GND
VCC
VCC
GND
GND
VCC
VCC
GND
GND
VCC
VCC
GND
GND
GND
GND
100k
100k
100k
GND
100k
100k
100k
100k
GND
GND
GND
GND
91k 1%
GND
VCC
100k
GND
91k 1%GND
GND
S7
S6
S4
GND
S7
S6
GND
S4
GND
3
1 GND
GND
2 NC
NC
5
3 NC
GND
6
4 GND
NC
7
5 NC
NC
8
6 NC
GND
9
7 S0
NC
10
8 S1
NC
11
9 GND
S0
12
10 S2
S1
13
11 S3
GND
14
12 LVL_ADJ
S2
15
13 LATCH_EN
S3
16
14 RESET
LVL_ADJ
17
15 GND
LATCH_EN
18
16 S7
RESET
19
17 S6
GND
20
18 S4
S7
21
19 RSSI
S6
22
20 GND
S4
TRM-XXX-TT
21
RSSI
4
22
GND
GND
NC
ANTENNA
NC
GND
GND
NC
NC
NC
NC
GND
ACK_EN
NC
MODE_IND
NC
GND
ACK_EN
PAIR
MODE_IND
C1
GND
ACK_OUT
PAIR
C0
C1
CMD_DATA_OUT
ACK_OUT
GND
C0
CMD_DATA_IN
CMD_DATA_OUT
S5
GND
VCC
CMD_DATA_IN
POWER_DOWN
S5
GND
VCC
GND
POWER_DOWN
GND
42
41
40
39
38
37
26
25
24
23
GND
GND
44 GND
GND
43
42
GND
41 GND
GND
GND
40
39
GND
36
38 VCC
35
37
34
36 GND
VCC
33
35
32
34 GND
GND
31
33
30
32 VCC
GND
29
31
28
30 GND
VCC
27
29 VCC
28
27
26
25
24
23
GND
S0
S1
GND
GND
S0
S2
S1
S3
GND
VCC
100k
100k
GND
GND
VCC GND
GND
GND
GND
GND
S5
GND
VCC
VCC
VCC
S5
GND
VCC
VCC
GND
TRM-XXX-TT
1
GND
2
43
91k 1%
S2
VCC
S3
91k 1%GND
VCC
VCC
GND
VCC
VCC
GND
GND
VCC
VCC
GND
GND
100k
100k
100k
100k
100k
GND
GND
GND
NC
3
1 GND
GND
2 NC
NC
5
3 NC
GND
6
4 GND
NC
7
5 NC
NC
8
6 NC
GND
9
7 S0
NC
10
8 S1
NC
11
9 GND
S0
12
10 S2
S1
13
11 S3
GND
14
12 LVL_ADJ
S2
15
13 LATCH_EN
S3
16
14 RESET
LVL_ADJ
17
15 GND
LATCH_EN
18
16 S7
RESET
19
17 S6
GND
20
18 S4
S7
21
19 RSSI
S6
22
20 GND
S4
TRM-XXX-TT
21
RSSI
4
22
GND
ANTENNA
GND
GND
NC
ANTENNA
NC
GND
GND
NC
NC
NC
NC
GND
ACK_EN
NC
MODE_IND
NC
GND
ACK_EN
PAIR
MODE_IND
C1
GND
ACK_OUT
PAIR
C0
C1
CMD_DATA_OUT
ACK_OUT
GND
C0
CMD_DATA_IN
CMD_DATA_OUT
S5
GND
VCC
CMD_DATA_IN
POWER_DOWN
S5
GND
VCC
POWER_DOWN
GND
GND
44
GND
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
44 GND
GND
43
42
GND
41 GND
40
39
GND
38
GND
37
36 GND
VCC
100k
35
33
GND
GND
34 VCC
GND
100k
32 GND
VCC
VCC GND
GND
GPIO
31
GND
RX
µ
30 GND
GND
TX
RX
29
28
GND
27 VCC
100k
26 VCC
25 GND
VCC
24
23
GND
GPIO
µ
VCC
TX
VCC
100k
GND
VCC
GND
TRM-XXX-TT
VCC
Figure 31: TT Series Transceiver Basic Application Circuit
Figure 32:
TT Series Transceiver Typical Application Circuit with External Microprocessor
GND
100k
In this example, C0 is high and C1 is low, so S0–S3 are inputs and S4–S7
are outputs. The inputs are connected to buttons that pull the lines high
and weak pull-down resistors to keep the lines from floating when the
buttons are not pressed. The outputs would be connected to external
application circuitry.
In this example, C0 is low and C1 is high, so S0–S3 are outputs and
S4–S7 are inputs. This is inverted from the circuit in Figure 31 making it the
matching device.
In this circuit, the Command Data Interface is connected to a
microcontroller for using some of the advanced features.
LATCH_EN is low, so the outputs are momentary.
The Command Data Interface is not used in this design, so CMD_DATA_IN
is tied high and CMD_DATA_OUT is not connected.
The microcontroller controls the state of the ACK_EN line. it can receive
a command, perform an action and then take the line high to send
Acknowledgement packets. This lets the user on the other end know that
the action took place and not just that the command was received.
ACK_OUT and MODE_IND are connected to LEDs to provide visual
indication to the user.
PAIR is connected to a button and pull-down resistor to initiate the Pair
Process when the button is pressed.
ACK_EN is tied high so the module sends acknowledgements as soon as it
receives a control message.
– 36 –
– 37 –
Antenna Considerations
Helpful Application Notes from Linx
The choice of antennas is a
critical and often overlooked
design consideration. The range,
performance and legality of an RF
link are critically dependent upon the
antenna. While adequate antenna
performance can often be obtained
by trial and error methods, antenna
Figure 33: Linx Antennas
design and matching is a complex
task. Professionally designed antennas such as those from Linx (Figure
33) help ensure maximum performance and FCC and other regulatory
compliance.
It is not the intention of this manual to address in depth many of the issues
that should be considered to ensure that the modules function correctly
and deliver the maximum possible performance. We recommend reading
the application notes listed in Figure 34 which address in depth key areas
of RF design and application of Linx products. These applications notes are
available online at www.linxtechnologies.com or by contacting Linx.
Linx transmitter modules typically have an output power that is higher
than the legal limits. This allows the designer to use an inefficient antenna
such as a loop trace or helical to meet size, cost or cosmetic requirements
and still achieve full legal output power for maximum range. If an efficient
antenna is used, then some attenuation of the output power will likely be
needed. This can easily be accomplished by using the LVL_ADJ line.
Helpful Application Note Titles
Note Number
Note Title
AN-00100
RF 101: Information for the RF Challenged
AN-00126
Considerations for Operation Within the 902–928MHz Band
AN-00130
Modulation Techniques for Low-Cost RF Data Links
AN-00140
The FCC Road: Part 15 from Concept to Approval
AN-00500
Antennas: Design, Application, Performance
AN-00501
Understanding Antenna Specifications and Operation
RG-00103
TT Series Transceiver Command Data Interface Reference Guide
Figure 34: Helpful Application Note Titles
It is usually best to utilize a basic quarter-wave whip until your prototype
product is operating satisfactorily. Other antennas can then be evaluated
based on the cost, size and cosmetic requirements of the product.
Additional details are in Application Note AN-00500.
The transceiver includes a U.FL connector as well as a line for the
antenna connection. This offers the designer a great deal of flexibility in
antenna selection and location within the end product. Linx offers cable
assemblies with a U.FL connector on one end and several types of
standard and FCC-compliant reverse-polarity connectors on the other end.
Alternatively, the designer may wish to use the pin and route the antenna to
a PCB mount connector or even a printed loop trace antenna. This gives
the designer the greatest ability to optimize performance and cost within
the design.
Note: Either the connector or the line can be used for the antenna, but
not both at the same time.
– 38 –
– 39 –
Interference Considerations
Pad Layout
The RF spectrum is crowded and the potential for conflict with unwanted
sources of RF is very real. While all RF products are at risk from
interference, its effects can be minimized by better understanding its
characteristics.
The pad layout diagram in Figure 35 is designed to facilitate both hand and
automated assembly.
Interference may come from internal or external sources. The first step
is to eliminate interference from noise sources on the board. This means
paying careful attention to layout, grounding, filtering and bypassing in
order to eliminate all radiated and conducted interference paths. For
many products, this is straightforward; however, products containing
components such as switching power supplies, motors, crystals and other
potential sources of noise must be approached with care. Comparing your
own design with a Linx evaluation board can help to determine if and at
what level design-specific interference is present.
External interference can manifest itself in a variety of ways. Low-level
interference produces noise and hashing on the output and reduces the
link’s overall range.
High-level interference is caused by nearby products sharing the same
frequency or from near-band high-power devices. It can even come from
your own products if more than one transmitter is active in the same area.
It is important to remember that only one transmitter at a time can occupy
a frequency, regardless of the coding of the transmitted signal. This type of
interference is less common than those mentioned previously, but in severe
cases it can prevent all useful function of the affected device.
Although technically not interference, multipath is also a factor to be
understood. Multipath is a term used to refer to the signal cancellation
effects that occur when RF waves arrive at the receiver in different phase
relationships. This effect is a particularly significant factor in interior
environments where objects provide many different signal reflection paths.
Multipath cancellation results in lowered signal levels at the receiver and
shorter useful distances for the link.
0.050"
(1.27)
0.050"
(1.27)
0.028"
(0.71)
0.065"
(1.65)
0.605"
(15.37)
0.045"
(1.14)
Figure 35: Recommended PCB Layout
Board Layout Guidelines
The module’s design makes integration straightforward; however, it
is still critical to exercise care in PCB layout. Failure to observe good
layout techniques can result in a significant degradation of the module’s
performance. A primary layout goal is to maintain a characteristic
50-ohm impedance throughout the path from the antenna to the module.
Grounding, filtering, decoupling, routing and PCB stack-up are also
important considerations for any RF design. The following section provides
some basic design guidelines.
During prototyping, the module should be soldered to a properly laid-out
circuit board. The use of prototyping or “perf” boards results in poor
performance and is strongly discouraged. Likewise, the use of sockets
can have a negative impact on the performance of the module and is
discouraged.
The module should, as much as reasonably possible, be isolated from
other components on your PCB, especially high-frequency circuitry such as
crystal oscillators, switching power supplies, and high-speed bus lines.
When possible, separate RF and digital circuits into different PCB regions.
Make sure internal wiring is routed away from the module and antenna and
is secured to prevent displacement.
– 40 –
– 41 –
Do not route PCB traces directly under the module. There should not be
any copper or traces under the module on the same layer as the module,
just bare PCB. The underside of the module has traces and vias that could
short or couple to traces on the product’s circuit board.
The Pad Layout section shows a typical PCB footprint for the module. A
ground plane (as large and uninterrupted as possible) should be placed on
a lower layer of your PC board opposite the module. This plane is essential
for creating a low impedance return for ground and consistent stripline
performance.
Use care in routing the RF trace between the module and the antenna
or connector. Keep the trace as short as possible. Do not pass it under
the module or any other component. Do not route the antenna trace on
multiple PCB layers as vias add inductance. Vias are acceptable for tying
together ground layers and component grounds and should be used in
multiples.
Each of the module’s ground pins should have short traces tying
immediately to the ground plane through a via.
Microstrip Details
A transmission line is a medium whereby RF energy is transferred from
one place to another with minimal loss. This is a critical factor, especially
in high-frequency products like Linx RF modules, because the trace
leading to the module’s antenna can effectively contribute to the length
of the antenna, changing its resonant bandwidth. In order to minimize
loss and detuning, some form of transmission line between the antenna
and the module should be used unless the antenna can be placed very
close (<1/8in) to the module. One common form of transmission line is a
coax cable and another is the microstrip. This term refers to a PCB trace
running over a ground plane that is designed to serve as a transmission line
between the module and the antenna. The width is based on the desired
characteristic impedance of the line, the thickness of the PCB and the
dielectric constant of the board material. For standard 0.062in thick FR-4
board material, the trace width would be 111 mils. The correct trace width
can be calculated for other widths and materials using the information in
Figure 36 and examples are provided in Figure 37. Software for calculating
microstrip lines is also available on the Linx website.
Trace
Board
Bypass caps should be low ESR ceramic types and located directly
adjacent to the pin they are serving.
Ground plane
A 50-ohm coax should be used for connection to an external antenna.
A 50-ohm transmission line, such as a microstrip, stripline or coplanar
waveguide should be used for routing RF on the PCB. The Microstrip
Details section provides additional information.
In some instances, a designer may wish to encapsulate or “pot” the
product. There are a wide variety of potting compounds with varying
dielectric properties. Since such compounds can considerably impact
RF performance and the ability to rework or service the product, it is
the responsibility of the designer to evaluate and qualify the impact and
suitability of such materials.
Figure 36: Microstrip Formulas
Example Microstrip Calculations
Dielectric Constant
Width / Height
Ratio (W / d)
Effective Dielectric
Constant
Characteristic
Impedance (Ω)
4.80
1.8
3.59
50.0
4.00
2.0
3.07
51.0
2.55
3.0
2.12
48.8
Figure 37: Example Microstrip Calculations
– 42 –
– 43 –
The module is housed in a hybrid SMD package that supports hand and
automated assembly techniques. Since the modules contain discrete
components internally, the assembly procedures are critical to ensuring
the reliable function of the modules. The following procedures should be
reviewed with and practiced by all assembly personnel.
Hand Assembly
Pads located on the bottom
Soldering Iron
of the module are the primary
Tip
mounting surface (Figure 38).
Since these pads are inaccessible
during mounting, castellations
that run up the side of the module Solder
have been provided to facilitate
PCB Pads
Castellations
solder wicking to the module’s
Figure 38: Soldering Technique
underside. This allows for very
quick hand soldering for prototyping and small volume production. If the
recommended pad guidelines have been followed, the pads will protrude
slightly past the edge of the module. Use a fine soldering tip to heat the
board pad and the castellation, then introduce solder to the pad at the
module’s edge. The solder will wick underneath the module, providing
reliable attachment. Tack one module corner first and then work around the
device, taking care not to exceed the times in Figure 39.
Warning: Pay attention to the absolute maximum solder times.
Absolute Maximum Solder Times
Hand Solder Temperature: +427ºC for 10 seconds for lead-free alloys
Reflow Oven: +255ºC max (see Figure 40)
Figure 39: Absolute Maximum Solder Times
Automated Assembly
For high-volume assembly, the modules are generally auto-placed.
The modules have been designed to maintain compatibility with reflow
processing techniques; however, due to their hybrid nature, certain aspects
of the assembly process are far more critical than for other component
types. Following are brief discussions of the three primary areas where
caution must be observed.
– 44 –
Reflow Temperature Profile
The single most critical stage in the automated assembly process is the
reflow stage. The reflow profile in Figure 40 should not be exceeded
because excessive temperatures or transport times during reflow will
irreparably damage the modules. Assembly personnel need to pay careful
attention to the oven’s profile to ensure that it meets the requirements
necessary to successfully reflow all components while still remaining
within the limits mandated by the modules. The figure below shows the
recommended reflow oven profile for the modules.
300
Recommended RoHS Profile
Max RoHS Profile
Recommended Non-RoHS Profile
255°C
250
235°C
217°C
Temperature (oC)
Production Guidelines
200
185°C
180°C
150
125°C
100
50
0
30
60
90
120
150
180
210
240
270
300
330
360
Time (Seconds)
Figure 40: Maximum Reflow Temperature Profile
Shock During Reflow Transport
Since some internal module components may reflow along with the
components placed on the board being assembled, it is imperative that
the modules not be subjected to shock or vibration during the time solder
is liquid. Should a shock be applied, some internal components could be
lifted from their pads, causing the module to not function properly.
Washability
The modules are wash-resistant, but are not hermetically sealed. Linx
recommends wash-free manufacturing; however, the modules can be
subjected to a wash cycle provided that a drying time is allowed prior
to applying electrical power to the modules. The drying time should be
sufficient to allow any moisture that may have migrated into the module
to evaporate, thus eliminating the potential for shorting damage during
power-up or testing. If the wash contains contaminants, the performance
may be adversely affected, even after drying.
– 45 –
General Antenna Rules
The following general rules should help in maximizing antenna performance.
1. Proximity to objects such as a user’s hand, body or metal objects will
cause an antenna to detune. For this reason, the antenna shaft and tip
should be positioned as far away from such objects as possible.
2. Optimum performance is obtained from a ¼- or ½-wave straight whip
mounted at a right angle to the ground plane (Figure 41). In many
cases, this isn’t desirable for practical or ergonomic reasons, thus,
an alternative antenna style such as a helical, loop or patch may be
utilized and the corresponding sacrifice in performance accepted.
OPTIMUM
USABLE
NOT RECOMMENDED
Figure 41: Ground Plane Orientation
plane as possible in proximity to the base of the antenna. In cases
where the antenna is remotely located or the antenna is not in close
proximity to a circuit board, ground plane or grounded metal case, a
metal plate may be used to maximize the antenna’s performance.
5. Remove the antenna as far as possible from potential interference
sources. Any frequency of sufficient amplitude to enter the receiver’s
front end will reduce system range and can even prevent reception
entirely. Switching power supplies, oscillators or even relays can also
be significant sources of potential interference. The single best weapon
against such problems is attention to placement and layout. Filter the
module’s power supply with a high-frequency bypass capacitor. Place
adequate ground plane under potential sources of noise to shunt noise
to ground and prevent it from coupling to the RF stage. Shield noisy
board areas whenever practical.
6. In some applications, it is advantageous to place the module and
antenna away from the main equipment (Figure 43). This can avoid
interference problems and allows the antenna to be oriented for
optimum performance. Always use 50Ω coax, like RG-174, for the
OPTIMUM
remote feed.
NOT RECOMMENDED
USABLE
CASE
3. If an internal antenna is to be used, keep it away
from other metal
components, particularly large items like
transformers,
batteries,
GROUND PLANE
NUT
PCB tracks and ground planes. In many
the space around the
(MAYcases,
BE NEEDED)
antenna is as important as the antenna itself. Objects in close proximity
to the antenna can cause direct detuning, while those farther away will
alter the antenna’s symmetry.
CASE
GROUND PLANE
(MAY BE NEEDED)
NUT
4. In many antenna designs, particularly ¼-wave whips, the ground plane
acts as a counterpoise, forming, in essence,
VERTICAL λ/4 GROUNDED
a ½-wave dipole (Figure 42). For this reason,
ANTENNA (MARCONI)
adequate ground plane area is essential.
DIPOLE
ELEMENT
The ground plane can be a metal case or
λ/4
ground-fill areas on a circuit board. Ideally, it
should have a surface area less than or equal
to the overall length of the ¼-wave radiating
element. This is often not practical due to
GROUND
PLANE
size and configuration constraints. In these
VIRTUAL λ/4
λ/4
instances, a designer must make the best use
DIPOLE
of the area available to create as much ground
Figure 43: Remote Ground Plane
E
I
Figure 42: Dipole Antenna
– 46 –
– 47 –
Common Antenna Styles
There are hundreds of antenna styles and variations that can be employed
with Linx RF modules. Following is a brief discussion of the styles most
commonly utilized. Additional antenna information can be found in Linx
Application Notes AN-00100, AN-00140, AN-00500 and AN-00501. Linx
antennas and connectors offer outstanding performance at a low price.
Whip Style
A whip style antenna (Figure 44) provides
outstanding overall performance and stability.
A low-cost whip can be easily fabricated from
a wire or rod, but most designers opt for the
consistent performance and cosmetic appeal of
a professionally-made model. To meet this need,
Linx offers a wide variety of straight and reduced
height whip style antennas in permanent and
connectorized mounting styles.
Figure 44: Whip Style Antennas
The wavelength of the operational frequency determines
234
an antenna’s overall length. Since a full wavelength
L=
F
MHz
is often quite long, a partial ½- or ¼-wave antenna
Figure 45:
is normally employed. Its size and natural radiation
L = length in feet of
resistance make it well matched to Linx modules.
quarter-wave length
The proper length for a straight ¼-wave can be easily
F = operating frequency
in megahertz
determined using the formula in Figure 45. It is also
possible to reduce the overall height of the antenna by
using a helical winding. This reduces the antenna’s bandwidth but is a great
way to minimize the antenna’s physical size for compact applications. This
also means that the physical appearance is not always an indicator of the
antenna’s frequency.
Specialty Styles
Linx offers a wide variety of specialized antenna
styles (Figure 46). Many of these styles utilize helical
elements to reduce the overall antenna size while
maintaining reasonable performance. A helical
antenna’s bandwidth is often quite narrow and the
antenna can detune in proximity to other objects, so
care must be exercised in layout and placement.
– 48 –
Loop Style
A loop or trace style antenna is normally printed
directly on a product’s PCB (Figure 47). This
makes it the most cost-effective of antenna
styles. The element can be made self-resonant or
externally resonated with discrete components,
but its actual layout is usually product specific.
Despite the cost advantages, loop style antennas
Figure 47: Loop or Trace Antenna
are generally inefficient and useful only for short
range applications. They are also very sensitive to changes in layout and
PCB dielectric, which can cause consistency issues during production.
In addition, printed styles are difficult to engineer, requiring the use of
expensive equipment including a network analyzer. An improperly designed
loop will have a high VSWR at the desired frequency which can cause
instability in the RF stage.
Linx offers low-cost planar (Figure 48) and chip
antennas that mount directly to a product’s PCB.
These tiny antennas do not require testing and
provide excellent performance despite their small
size. They offer a preferable alternative to the often
problematic “printed” antenna.
Figure 46: Specialty Style
Antennas
– 49 –
Figure 48: SP Series
“Splatch” and uSP
“MicroSplatch” Antennas
Regulatory Considerations
Note: Linx RF modules are designed as component devices that require
external components to function. The purchaser understands that
additional approvals may be required prior to the sale or operation of
the device, and agrees to utilize the component in keeping with all laws
governing its use in the country of operation.
When working with RF, a clear distinction must be made between what
is technically possible and what is legally acceptable in the country where
operation is intended. Many manufacturers have avoided incorporating RF
into their products as a result of uncertainty and even fear of the approval
and certification process. Here at Linx, our desire is not only to expedite the
design process, but also to assist you in achieving a clear idea of what is
involved in obtaining the necessary approvals to legally market a completed
product.
For information about regulatory approval, read AN-00142 on the Linx
website or call Linx. Linx designs products with worldwide regulatory
approval in mind.
In the United States, the approval process is actually quite straightforward.
The regulations governing RF devices and the enforcement of them are
the responsibility of the Federal Communications Commission (FCC). The
regulations are contained in Title 47 of the United States Code of Federal
Regulations (CFR). Title 47 is made up of numerous volumes; however,
all regulations applicable to this module are contained in Volume 0-19.
It is strongly recommended that a copy be obtained from the FCC’s
website, the Government Printing Office in Washington or from your local
government bookstore. Excerpts of applicable sections are included
with Linx evaluation kits or may be obtained from the Linx Technologies
website, www.linxtechnologies.com. In brief, these rules require that any
device that intentionally radiates RF energy be approved, that is, tested for
compliance and issued a unique identification number. This is a relatively
painless process. Final compliance testing is performed by one of the many
independent testing laboratories across the country. Many labs can also
provide other certifications that the product may require at the same time,
such as UL, CLASS A / B, etc. Once the completed product has passed,
an ID number is issued that is to be clearly placed on each product
manufactured.
– 50 –
Questions regarding interpretations of the Part 2 and Part 15 rules or the
measurement procedures used to test intentional radiators such as Linx RF
modules for compliance with the technical standards of Part 15 should be
addressed to:
Federal Communications Commission
Equipment Authorization Division
Customer Service Branch, MS 1300F2
7435 Oakland Mills Road
Columbia, MD, US 21046
Phone: + 1 301 725 585 | Fax: + 1 301 344 2050
Email: labinfo@fcc.gov
ETSI Secretaria
650, Route des Lucioles
06921 Sophia-Antipolis Cedex
FRANCE
Phone: +33 (0)4 92 94 42 00
Fax: +33 (0)4 93 65 47 16
International approvals are slightly more complex, although Linx modules
are designed to allow all international standards to be met. If the end
product is to be exported to other countries, contact Linx to determine the
specific suitability of the module to the application.
All Linx modules are designed with the approval process in mind and thus
much of the frustration that is typically experienced with a discrete design is
eliminated. Approval is still dependent on many factors, such as the choice
of antennas, correct use of the frequency selected and physical packaging.
While some extra cost and design effort are required to address these
issues, the additional usefulness and profitability added to a product by RF
makes the effort more than worthwhile.
– 51 –
Linx Technologies
159 Ort Lane
Merlin, OR, US 97532
Phone: +1 541 471 6256
Fax: +1 541 471 6251
www.linxtechnologies.com
Disclaimer
Linx Technologies is continually striving to improve the quality and function of its products. For this reason, we
reserve the right to make changes to our products without notice. The information contained in this Data Guide
is believed to be accurate as of the time of publication. Specifications are based on representative lot samples.
Values may vary from lot-to-lot and are not guaranteed. “Typical” parameters can and do vary over lots and
application. Linx Technologies makes no guarantee, warranty, or representation regarding the suitability of any
product for use in any specific application. It is the customer’s responsibility to verify the suitability of the part for
the intended application. NO LINX PRODUCT IS INTENDED FOR USE IN ANY APPLICATION WHERE THE SAFETY
OF LIFE OR PROPERTY IS AT RISK.
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OR FOR ANY OTHER BREACH OF CONTRACT BY LINX TECHNOLOGIES. The limitations on Linx Technologies’
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limitation, breach of contract, breach of warranty, strict liability, or negligence. Customer assumes all liability
(including, without limitation, liability for injury to person or property, economic loss, or business interruption) for
all claims, including claims from third parties, arising from the use of the Products. The Customer will indemnify,
defend, protect, and hold harmless Linx Technologies and its officers, employees, subsidiaries, affiliates,
distributors, and representatives from and against all claims, damages, actions, suits, proceedings, demands,
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Products sold by Linx Technologies to Customer. Under no conditions will Linx Technologies be responsible for
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The stylized Linx logo, Wireless Made Simple, WiSE, CipherLinx and the stylized CL logo are trademarks of Linx Technologies.
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