A Guide to Cables, Connectors, &

A GUIDE TO CABLES,
CONNECTORS, & ADAPTERS
• What do Cables and Cable Connectors Do?
03
• Components of Coaxial Cables
03
• Determining Cable Loss
04
• Size Comparison
06
• Coaxial Cable Connectors
07
• The Threading (Female or Male)
08
• The Center Pin (RP)
09
• Connections
11
• Connector Chart
12
• Adapters vs. Cables
13
W H AT D O C A B L ES
& C A B L E CO N N E C TO R S D O ?
Coaxial cables provide the essential link between an RFID reader and an antenna. They can also
be used to connect auxiliary devices like antenna hubs and multiplexers in certain applications.
Coaxial cables are energy conductors consisting of a copper core that is insulated by both metal
and rubber. The energy generated by the RFID reader is sent via the antenna port of the reader,
into the first connector, through the cable, out the other connector, and into the antenna. The
better insulated the cable is, the less energy lost during the process. [For a more detailed look at
RFID energy flow in a system read: RF Physics: How Does Energy Flow in an RFID System].
Antenna cables terminate at both ends in a connector; but, connectors, as well as adapters, can
also be sold separately.
CO M P O N E N T S
O F COA X I A L C A B L ES
Cables have one job – to transfer energy; but, just as important, cables must be properly built
to combat potential energy loss. Energy loss happens in every system; the key here is to understand how it is lost from a cable in order to fight it.
Three components make up a coaxial cable, and are important to understand in order to select
the correct cable for an application.
Length – The longer the cable, the farther the energy has to travel. No antenna cable
is perfectly insulated; so, the farther the energy travels, the more energy it will lose.
In some applications, the reader is farther from the antenna due to the nature of the
application. If a long cable must be used, it is important to use the appropriate level
of insulation required to combat loss.
Insulation Rating – The higher the insulation rating, the thicker and more protected
the cable. The most common ratings used with UHF coaxial cables are 195 series,
240 series, and 400 series. The downside to a thicker, more insulated cable is that the
cable is less pliable and could be difficult to position in a tight space.
Connectors – Connectors are located at both ends of a cable, and their type is determined by the connectors on the reader and antenna being used in the application.
Later, this guide will walk through what types of connectors are compatible with each
other.
03
DETERMINING
C A B L E LO S S
Cable loss is the amount of power lost from the cable and is determined by the insulation rating
and length of the cable. For applications that need a system running at maximum power to
provide long read range or for tracking at high speeds - the reader’s transmit power, cable loss,
and antenna gain will play key roles. Below is a chart documenting cable loss by length for each
insulation rating. This chart shows the correlation between the two so that, if the cable must be
lengthened, a higher insulation rating can be used to offset the loss.
04
DETERMINING
C A B L E LO S S
(continued)
*Of note, because power is being measured on the decibel scale, for every 3 dB reduction, the power is
cut in half. A reduction of 6 dB would be only 25% of the original power setting, and so on. Likewise, for
every 3 dB increase, the transmitted power doubles.
If an application isn’t getting the desired read range, transmit power on the reader and cable
loss can easily be calculated and adjusted. If the application is losing too much energy from
the cable, consider decreasing the length and/or increasing the insulation rating to ensure
more energy is received by the antenna.
To easily calculate the amount of power that the RFID antenna is receiving, see the equation
below.
Transmit Power (dBm) - Cable Loss (dB) = Antenna Input
Additionally, if the power entering the antenna isn’t quite enough, a higher gain antenna can
be used. To calculate the total system output of power at the antenna, the following equation
can be used:
Transmit Power (dBm) - Cable Loss (dB) + Antenna Gain (dB) = System Output
30 dBm-3 dB+6 dB=33 dBm
Please note that most regions limit the total power output from the point of the antenna. For
example, FCC regulations limit the total power output to 4 watts or 36 dBm. Be sure to check
the regulations for your region to ensure your system is in compliance.
[For more tips on improving your RFID system’s read range, read 6 Factors that Affect Read
Range.]
05
SIZE
CO M PA R I S O N S
N-TYPE MALE
RP-TNC MALE
SMA MALE
PENCIL ERASER
(FOR SCALE)
CO N N E C TO R S
I N S U L AT I O N R AT I N G S
400 Series
INSULATION RATING
240 Series
INSULATION RATING
195 Series
INSULATION RATING
PENCIL
(FOR SCALE)
06
COA X I A L C A B L E
CO N N E C T I O N S
Connecting a cable from the antenna to the reader in an RFID system isn’t difficult – but purchasing
the correct cable that will join the hardware together can be a tedious task. Quite a few types of
cable connectors can be used, and each one is dictated by the connectors on the hardware. The
chart below walks through the most popular types of coaxial connectors with a little information
about each.
COAXIAL CONNECTOR
RP-TNC
A derivative of a TNC connector, the RP-TNC
connector is one of the most frequently used cable
connectors for a UHF RFID system.
SMA
SMA connectors are known for their small size in
comparison to other typical UHF connectors, and are
about the size of a pencil eraser.
N-TYPE
N-TYPE connectors are almost twice as big as an
RP-TNC connector, so they are the largest connectors
commonly used in UHF RFID systems.
IMAGE
RP-TNC MALE
SMA MALE
N-TYPE MALE
TNC
A relative of the RP-TNC, the TNC connector is the
normal polarity version.
TNC MALE
RP-SMA
A derivative of an SMA connector, an RP-SMA is
simply an SMA connector with the polarity reversed.
RP-SMA MALE
BNC
BNC is a less commonly used connector in UHF RFID
systems, but is similar in size to a TNC connector.
BNC connectors allow for quicker attachment than
most others, but they also are more likely to loosen
over time.
BNC MALE
07
THE THREADING
( M A L E VS. F E M A L E )
On a coaxial cable connector or adapter, the threading is either on the outside of the connector
in plain view, or on the inside of the connector. Two terms are used for each of these types of
connectors:
FEMALE / JACK
A Female, or Jack, connector is characterized by having the threading on the
OUTSIDE of the connector.
MALE / PLUG
A Male, or Plug, connector is characterized by having the threading on the
INSIDE of the connector.
08
THE CENTER PIN
( N O R M A L V S. R E V E R S E P O L A R I T Y )
The center pin of a coaxial connector is the component that conducts the RF energy and is one key
to identifying what type it is and with what it is compatible. There are two options when it comes to
the center pin of a connector, normal polarity or reverse polarity.
NORMAL POLARITY
Examples include: TNC, SMA, N-TYPE, BNC
Female/Jack – A normal female/jack connector has the threading on the outside
and a hole in the center to receive the male/plug’s center pin.
Male/Plug – A male/plug connector has the threading on the inside and a metal
center pin to insert into a female/jack connector.
Key Takeaway: Normal polarity = center pin is in the MALE connector.
Normal Polarity FEMALE
Outside Threading
Hole for Center Pin
Normal Polarity MALE
Inside Threading
Center Pin
09
THE CENTER PIN
( N O R M A L V S. R E V E R S E P O L A R I T Y )
(continued)
REVERSED (RP) POLARITY
Examples include: RP-TNC, RP-SMA
Female/Jack - A reverse-polarity female/jack connector still has the threading on
the outside, but, because the polarity has been reversed, the center pin is on the
inside of this connector.
Male/Plug – A reverse-polarity male/plug connector still has the threading on the
inside, but because the polarity has been reversed, the hole is on the inside of
this connector.
Key Takeaway: Reverse polarity = center pin is in the FEMALE connector.
Reversed Polarity (RP) FEMALE
Outside Threading
Center Pin
Reversed Polarity (RP) MALE
Inside Threading
Hole for Center Pin
10
CO N N E C T I O N S
Ensuring two connectors will properly join and work as expected can sometimes be a confusing
and tedious task. For example, if an RFID reader has an RP-TNC Female connector, should it
connect to a RP-TNC Male, a TNC Female, or a TNC Male? These four types have similar names
and sizes, and ordering the incorrect type can add several days’ worth of delay to a project.
Below are a few rules to go by, as well as a visual connection guide to simplify the process.
Rule #1 – Similar types connect.
Example: TNC connects to a TNC; SMA connects to an SMA
Rule #2 - Similar polarities connect.
Example: RP-SMA connects to an RP-SMA; RP-TNC connects to an RP-TNC
Rule #3 – Opposite genders/threading types connect.
Example: SMA Male connects to an SMA Female,RP-TNC Male connects to an
RP-TNC Female
MALES
FEMALES
TNC MALE
TNC FEMALE
RP-TNC MALE
RP-TNC FEMALE
SMA MALE
SMA FEMALE
RP-SMA MALE
RP-SMA FEMALE
N-TYPE MALE
N-TYPE FEMALE
BNC MALE
BNC FEMALE
11
CO N N E C TO R C H A RT
RP-TNC MALE
RP-TNC FEMALE
SMA MALE
SMA FEMALE
N-TYPE MALE
N-TYPE FEMALE
RP-SMA MALE
RP-SMA FEMALE
TNC MALE
TNC FEMALE
BNC MALE
BNC FEMALE
12
COA X I A L A DA PT E R S
An adapter is used to join any two coaxial connectors that would otherwise be incompatible.
There are two scenarios where a coaxial adapter may be required:
1. If one or both connectors on a cable is incompatible
with the RFID reader or antenna.
Purchasing a cable with the incorrect connectors
can happen easily; not only are some of them
similarly named, but they appear similar in
pictures as well.
2. To save money when experimenting with different
antennas and readers.
If an application is still in the testing phase,
several different antennas and/or readers can
be purchased for experimentation. Instead
of purchasing several cables with different
connectors to match each reader/antenna
combination, one cable and a few different
adapters can be purchased instead. This can
save time and money during testing.
13
Contact
The
RFID
Experts
If you have any additional questions about if RFID is right for
your application, or about connectors & adapters, don't hesitate
to contact us.
Phone: 1.205.383.2244
Email: sales@atlasRFIDstore.com
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