Model 35 - Krohn-Hite Corporation
Model 35
170Hz to 25.6MHz, 24dB/Octave
Butterworth Tunable Active
Plug-In Filter Card
Operating Manual
Service and Warranty
Krohn-Hite Instruments are designed and manufactured in accordance with sound
engineering practices and should give long trouble-free service under normal operating
conditions. If your instrument fails to provide satisfactory service and you are unable to
locate the source of trouble, contact our Service Department at (508) 580-1660, giving all
the information available concerning the failure.
DO NOT return the instrument without our written or verbal authorization to do so. After
contacting us, we will issue a Return Authorization Number which should be referenced on
the packing slip and purchase order. In most cases, we will be able to supply you with the
information necessary to repair the instrument, avoiding any transportation problems and
costs. When it becomes necessary to return the instrument to the factory, kindly pack it
carefully and ship it to us prepaid.
All Krohn-Hite products are warranted against defective materials and workmanship. This
warranty applies for a period of one year from the date of delivery to the Original Purchaser.
Any instrument that is found within the one year warranty period not to meet these
standards, will be repaired or replaced. This warranty does not apply to electron tubes,
fuses or batteries. No other warranty is expressed or implied.
Krohn-Hite Corporation reserves the right to make design changes at any time without
incurring any obligation to incorporate these changes in instruments previously purchased.
Modifications to this instrument must not be made without the written consent of an
authorized employee of Krohn-Hite Corporation.
MODEL 35
170Hz to 25.6MHz
LOW-PASS BUTTERWORTH
PLUG-IN FILTER CARD
OPERATING AND MAINTENANCE
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PLUG-IN FILTER CARDS
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I..FL..I KRCHN-HITE
~ COFlPOFl.A.TION
255 Bodwell Street, Avon , MA 02322-9987
Tel: (508)580-1660; Fax: (508)583-8989
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Table of Contents
Model 35
Table of Contents
1.0 GENERAL DESCRIPTION
1.1 INTRODUCTION
1.2 SPECIFICATIONS
1.2.1 Filter Ch ar ac te r is t ics
1.2.2 Input
1.2.3 Output
1.2.4 General
2.0 OPERATION
2.1 INTRODUCTION
2.2 TURN-ON PROCEDURE
2.3 SELF-TEST fEATURE
2.4 JUMPER SETTINGS FOR FRONT AND REAR PANEL OPERATION
2.5 FRONT PANEL CONTROLS AND DISPLAY
2.5.1 Data Keys
2.5.2 [MODE] Key
2.5.3 [TYPE] Key
2.5.4 Channel
2 .5.5 Gain Set
2.5.6 Input Overload
2.5.7 Output Overload
2.5.g ICE] Clear Entry Key
2.5.9 lALL CHANNEL] Key
2.5.10 Input Ohms (Labeled White)
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1-1
1-1
1-1
1-1
1-2
1-2
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3.0 I£EE-488 STn (GPID) PROGRAMMING
3.1 INTRODUCTION
3.2 FILTER TYPE
3.3 MODE OF OPERATION "
3.4 DEVICE CLEAR
3-1
3-1
3 -1
3-1
3-1
4.0 INCOMING ACCEPTANCE
4.1 INTRODUCTION
4.2 TEST EQUlPMENT REQUIRED
4.3 INITIAL SETTINGS
4.4 DC OUTPUT LEVEL CHECKS
4.5 GAIN ACCURACY CHECK
4.6 DISTORTION CHECK
4.7 SQUAREWAVE RISE AND FALL TIME CHECK
4.8 FREQUENCY CALIBRATION CHECK
4.9 WIDEBAND NOISF CH ECK
4.10 STOPBAND ATTENUATION C H E C K
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Model 35
Table of Contents
ii
Model 35
Table of Contents
Model 35 Plug-In Filter Card
iii
Moclel35
Section 1 - General Description
SECTION 1
GENERAL DESCRIPTION
1.1 INTRODUCTION
The Model 35 is a low-pass, Butterworth (maximally flat) filler card, used in the Models 3905B and 3916B
mainframes, providing 24GB/octave rolloff with a minimum stopband attenuation of up to lOOdB. The Model
35 covers the frequency range of 170Hz to 25.6MHz with 2Vz digits of resolution.
The filter card has selectable AC or DC coupling and selectable 1M or 50 ohm impedance. Programmable input
gains of up to 20dB and output gains of up to 26dB are standard.
The Mode135 also has the capability to be configured in an Amplifier By-Pass mode to operate as an amplifier,
by-passing the filter. This gives the user the ability to amplify without filtering when so desired.
The Model 35 is one of many Krohn-Hite filter cards used in conjunction with two GPIB programmable
mainframes; the 3 1/2' high Model 3905B (5 plug-in card chassis) or the Model 3916B (16 plug-in card chassis).
1.2 SPECIFICATIONS
1.2.1 FILTER CHARACTERISTICS
Filter Type: 4-Pole, Butterworth, Low-Pass.
Tunable Cutoff Frequency Range: 170Hz (0 25.6MHz.
Frequency Response:
FreQuency Range
Resolution
170Hz \0 2.56kHz
10Hz
2,6kHz to 25.6kHz
100Hz
26kHz to 256kHz
1kHz
260kHz to 2,56MHz
10kHz
2.6MHz \0 25.6MHz
100kHz
Cutoff Frequency Accuracy: ±2% to 2.56MHz, =5% to 25.6MHz.
Attenuation Slope: 24dB/Octave.
Stopband Attenuation: 100dB to 1MHz, 80dB at 1OM Hz, 70dB at 30MHz, 60dB at 50MHz, 50dB to lOOMHz.
Amplified Bypass Mode Bandwidth: >50MHz..
Amplified Bypass Mode Rise and Fall Time: <7ns with OdB input gain 6dB output gain, < IOns with
input or output gain. <5% ringing or overshoot.
+ 20dB
1.2.2 INPUT
Input/Output Coupling: AC or DC. AC coupling cutoff is approximately 16Hz at the input and 10Hz at the
output with a 50Q termination. Note that the internal 50Q input termination is before the AC coupling.
Input Impedance: Selectable 1MQ or 50Q, =2%, shunted by 45pF.
Passband Response: =O.2dB up to 2.56MHz, =0.5dB to 25.6MHz.
Input Gain (Pre-Filter): OdB, + lOdB, +2OdB =O.ldB.
Maximum Input Signal: = 1.5V peak with OdB input gain, reduced in proportion to input gain selected.
Input DC Blocking Voltage: 200V Note that the internal input termination is before the AC coupling and can
only tolerate 7Vrms when ON.
1-1
Section 1 - General Description
Model 35
Maximum Input Without Damage: 12Vrms with input terminator OFF, 7Vrms with input terminator ON.
1.2.3 OUTPUT
Maximu m Ou tpu t Signal: ± 3V peak open cireui t, ± 1.5V peak in to 50Q .
Output Gain (Post- Filter): (kiB, HidE,
+2Ck:iB, +26d B, ± 0.1dB.
Output Impedance: SOQ, ±2%.
Distortion (lVrms sinewave): >-6O<1B below signal up to 100kHz (0.1 %) . All harmonics below 50dB to 1MHz;
below 40dB above 1MHz.
Output DC Offset: Adjustable to Zero.
Output DC Offset Drift: ±0.5mVtC referred to input.
Noise Spectral Density (10kHz to l00MHz referred to input): Below-128dBmlHz into 50 ohms. This translates
into a wideband noise power or voltage for a 30MHz BW of below -53dBm or O.50mVrms referred to input.
Spurious Signals: Below --80dBm to 65MHz; below -75dBm to l00MHz. Referred to input, represented in
voltage form: 22J.lV and 40.uV respectively.
1.2.4 GENERAL
Input/Output Connectors: BNe.
Power: 8 watts.
Weight 1.75 lbs, (.8kg) net.
Operating Temperature: O°C to 50°e.
Specifications apply at 25°C ±10°C,
Specifications subject to change without notice.
NOTE: The Model 35 filter card must be used with the Model 39058 or 39168 mainframes.
1-2
Section 2 - Operation
Model 35
SECTION 2
OPERATION
2.1 INTRODUCTION
The Model 35 low-pass filter card covers the frequency range from 170Hz to 25.6MHz. It is one of a series of
filter cards available for the 5 plug-in card mainframe, Model 3905B or the 16 plug-in card mainframe, Model
3916B mainframe. All filter parameters are programmable via the mainframes front panel or remotely over the
IEEE-488 (GPIB) bus. For detailed information of the front panel controls and remote programming. refer to
Section 2 and 3 of the Model 3905N/3916B mainframe's Operating and Maintenance Manual. Section 2.4 of
this manual briefly describes the operation of the principal front panel controls and data key operation.
2.2 TURN-ON PROCEDURE
a. The line voltage range of the Model 3905B/3916B mainframe has been preset at the factory for either 115V
or 230V operation. This range switch is located internally if a line voltage change is required. Check to see
that a fuse with the correct rating is in the fuse receptacle.
b. Make certain that the POWER switch on the front panel of the unit is in the OFF position.
c. Plug the line cord into the unit first, then into an ac outlet.
CAUTION
..:.':....
':'.'
.,.;.
',:.
For safety purposes, the line cord must be connected to a grounded
3-t enninal ac outlet. B ecause of'potent ially dangerous voltages thai
exist within the mainframe, the covers should be removed only by
qualified personnel.
d. If the Model 3905B/3916B is remotely programmed via the IEE E -488 (GPIB) bus, connect the bus cable
to the rear panel 24 position "D" connector at this time. Programming information is provided in Section 3
of the Model 3905B/3916B Operating and Maintenance Manual, with additional information in Section 3
of this manual.
e. The POWER switch is a toggle type, located on the front panel of the Model 3905B/3916B. After
familiarizi ng yourself with the self-test feat ure described next, turn-on the Model 3905B/3916B.
2.3 SELF·TEST FEATURE
When turned 0 n, the Model 3905B/3916B mierop roccssor pc rft irrn s a Sci f-Tcst ro utine whereby the en tire RAM
and ROM operation is verified. During the test, the front panel LEDs and display will light up sequentially.
If there is a malfunction in the microprocessor, such as a defective RAM or ROM. the sequence will stop and
the word "bAd" will appear in the display, followed by a number from 1 to 3. Refer to Section 7.6, Digital Circuit
Maintenance, to find which RAM or ROM is defective; otherwise, when the Self-Test program is complete, the
Model 3905B/3916B will return to the last set-up prior to turning off the unit.
The Model 3905B/3916B is now ready to be programmed for operation.
2-1
Section 2 - Operation
Model 35
2.4 JUMPER SETIINGS FOR FRONT AND REAR PANEL OPERATION
To achieve clean high frequency signal performance from the rear panel input and output ENCs, it is necessary
to disconnect the cabling connecting the front panel ENCs by moving the two jumpers on jumper blocks J201
(for input) and J517 (for output) shown in Figure 2.1 below. The Model 35 filter cards are shipped with the
jumpers set with front panel BNG; active.
INPUT
,
~
REAR ONLY G[ID
FRONT &
REAR
-
,
<,
<,
0 ~
~
r
~
~
--
/
0
OUTPUT
0
<,
,
­­
~
[]I]] REAR ONLY
El 0
0 0
,
-,
/
r
<,
FRONT &
REAR
Figure 2.1 Front and Rear panel Jumper Blocks
2.5 FRONT PANEL CONTROLS AND DISPLAY
2.5.1 DATA KEYS
Data entry keyboard controls, [0]-[9] and [.], and asso ciated 4 digit display set the numeric value of the parameter
selected. Ifa cu toff freg ue ncy of 1.5kHz is reg uired, press the [1] l-][5] data keys, then press [Kl LO] and [FREQ J
parameter keys. The cutoff frequency will be indicated in the 4 digit display .
2.5.2 [MODE} KEY
Indicates the mode of operation in the channel displayed, alternating between low-pass, "L.P." and amplifier
by-pass, "GAin", which disconnects the filter.
2.5.3 [TYPE] KEY
Displays "bu.", indicating Butterworth filter.
2.5.4 CHANNEL
The two channel controls [ft][ ~ ] and associated display, increment or decrement the channel setting. When
held , the Model 3905B/3916B will cycle through all the channe ls continuously.
2.5.5 GAIN SET
Input and OutpuL gain is controlled by the two GAIN SET controls [ft][ ~ ] and associated two digit displays.
Input gain is selectable to OdB, lOdB or 2OdB. Output gain is selectable to OdB, 6dB , 20dB or 26dB.
2.5.6 INPUT OVERLOAD
With OdB Input gain, the input overload indicator will turn on at approximately ± 1.6V peak. At lOdE,
approximately ±O.5V peak. At 20dB , approximately ::to.16V pe ak.
2.5.7 OUTPUT OVERLOAD
The output overload indicator will light at approximately ±3.2V peak output with the output not terminated,
or ± 1.6V peak output with the output terminated, for all gain settings except OdB output gain. For OdBoutput
gain the values are 1/2.
Model 35
Section 2 - Operation
2.5.8 [CEl CLEAR ENTRY KEY
Display will reset to the previous entry or toggle between present and previous settings.
2.5.9 [ALL CHANNEL] KEY
When on, parameter changes will be made simultaneously to all identical filter channels.
2.5.10 INPUT OHMS (Labeled White)
Pressing [SECOND FUNCTION], then input GAIN SET [[ ~ ][ ~ ], will indicate in the main display the current
input termination setting; either "e50&" (50 ohms) or "bhib" (1M). If "950&" is in the display, repeat the
[SECOND FUNCTION] GAIN SET [[ fi][ U] only again, then the input termination will be switched to "ehie.".
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Section 2 - Operation
Model 35
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Section 3 - IEEE-488 STD (GPIB) Programming
Model 35
SECTION 3
IEEE-488 STD (GPIB) PROGRAMMING
3.1 INTRODUCTION
Complete information on remote programming is incorporated in the Model 3905B/3916B mainframe Operat­ ing and Maintenance Manual. Detailed information about the filter type, modes of operation and device clear
command not described in the 3905B/3916B manual are specified below.
3.2 FILTER TYPE
- - --
----+)
DJ
3.3 MODE OF OPERATION ­
I
Low-Pass
2
3.4 DEVICE CLEAR
Butterworth
)
Amplifier
By-Pass
INPUT GAJN
OdB
OUTPUT } 3A1N:' .
6dB
R E SP Or-:J S ~':'"
Butterworth
MODE.. · ·
Low-Pa ss
CUTOFF FREQUENCY
1MHz
COUPLING:
DC
INPUT OHMS
;.;
50 Ohms
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Section 3 - IEEE-488 STD (GPfB) Programming
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Model 35
Section 4 - Incoming Acceptance
Model 35
SECTION 4
INCOMING ACCEPTANCE
4.1 INTRODUCTION
The following procedure should be used to verify that the Model 35 filter card, inserted in a Model 3905B or
3916B mainframe, is operating within specifications. These checks may be used (or incoming acceptance and
periodic performance checks. Tests must be made with all covers in place and operating (or a minimum time of
112 hour to reach thermal equilibrium. If not operating within specifications, refer to Section 5, Calibration,
before attempting any detailed maintenance. Before testing, follow the initial set-up and operating procedure
in Section 2 of this manual and the Model 3905B/3916B Operating and Maintenance Manual.
4.2 TEST EQUIPMENT REQUIRED
The test equipment below is required to perform the following tests:
II.
DC Voltmeter (DVM), capable of measuring 1mV to 20Y; Fluke 8000 or equivalent.
b. AC RMS Voltmeter, capable of measuring 100.uV to 10Vrms and useful bandwidth to 25MHz, Fluke 8920A
or equivalent.
c. Squarewave Source ,2Vp-p squ<'lrewave with rise and fall times <50S with <5% overshoot or ring, HP8012B
or equivalent.
d. Low Distortion Sinewave Signal Source, <0.05% distortion to 100kHz, 0.1 % to 1MHz, Krohn -Hite Model
4200B or equivalent.
e. Distortion Analyzer. capable of measuring distortion to 1MHz, Krohn-Hite Model 6900B or equivalent.
f. Sinewave Signal Source, covering the frequency range from IMHz to 1ooMHz, Tektronix Model 191 or
eq uivalen t.
g. Spectrum Analyzer, HP Model tat'Twith RF section 8553B and IF section 8552B or equivalent.
h. Oscilloscope, lOOMHz bandwidth, Tektronix Model 2245A or equivalent.
4.3 INITIAL SETTINGS
Input ohms: 50
Input Gain: OdB
Input Coupling: DC
Cutoff Frequency: 10MHz
Output Gain: GdB
Overload Mode: 2
Fi I ter Mode: LP
NOTE: Good "high frequency techniques" should be used at all times, which includes the use ofgood qualily 50
ohm cabling for signal connections to and from the jilter:
4.4 DC OUTPUT LEVEL CHECKS
Connect the DVM set for DC operation to the filter Output.
Measure DC level for all Input and Output gain settings.
Should be <±lOmVdc.
4-1
Section 4 - Incoming Acceptance
Model 35
4.5 GAIN ACCURACY CHECK
Disconnect the DVM and connect the Fluke 8920A to the filter Output.
Connect a 0.1Vrrns, 1kHz signal to the input (note that the filter Input is set for 50 ohms and will terminate a
50 ohm source producing a factor of2less in amplitude).
Set the filter Output gain for OdB.
Set the Fluke 8920A for AC relative dB measurements, and zero reference the Fluke.
Check each Input and Output gain selling by switching each one up from OdB independently.
All dB readings should be within O.ldB of the filter gain setting.
4.6 DISTORTION CHECK
Disconnect the Fluke 8920A from the filter Output.
Set the filter for OdB Input gain and 6dB Output gain.
Set the signal source for 1Vrrns, 1kHz, sincwavc and connect to the filter Input.
Connect the Distortion Analyzer to the l'ilter Output through a 50 ohm cable terminated at the analyzer end.
Measure the distortion at the following frequencies:
Frequency
1kHz
100kHz
1MHz
Tolerance
0.1 %
0.1%
0.3%
If necessary, verify that the signal sou rce's distortion is below the above readings by measuring it separately.
4.7 SQUAREWAVE RISE AND FALL TIME CHECK
Disconnect the distortion analyzer and sinewave signal source from the filter.
Set the filter for GAIN mode.
The filter Input and Output gain should be OdB and 6dB respectively, and Inpul Ohms set to 50.
Set the filter coupling to AC.
Connect the niter Input using a 50 ohm cable to the squarewave source set for 2Vp-p, 2.5MHz, squarewave.
Connect the filter Output to an oscilloscope with a 50 ohm cable terminated at the oscilloscope end.
Observe on the scope that overshoot and ringing is <5%.
Measure the rise and fall time from the 10 % and 90% waveform points.
It should be <7ns.
Set the squarewave source for 0.2Vp-p.
Check the Output waveform first with 20dB Input gain and then with 26dB Output gain for <5% overshoot
and ringing, and < 10ns rise and fall time.
4.8 FREQUENCY CALIBRATION CHECK
Set the filter for the initial setting at the beginning of this Section.
Connect the filter Input via a 50 ohm cable to a 1Vrms, 1kHz, sinewavc signal source.
Connect the Fluke 8920A to the Output of the filter with a 50 ohm cable.
Set the Fluke for relative dB operation.
Set the filter for a cutoff frequency of 1kHz and GAIN mode.
Zero reference the Fluke.
Set the filter for LOW-PASS (LP) mode and measure the drop in dB on the Output.
It should be within -2.67dB to -3.37dB for a ±2% calibration range.
4-2
Model 35
Section 4 - Incoming Acceptance
Set the sinewave generator and filter cutoff to the following frequencies and zero referencing the Fluke in the
filter GAIN mode, measure the drop in gain on the Output of the filter when switching the filter to th e LP
mode.
Freguency
1kHz
10kHz
100kHz
1MHz
10MHz
dB at Cutoff Range % Error Spec
-2.67dB to -3.37dB
±2%
-2.67dB to -3.37dB
±2%
-2.67dB to -3.37dB
±2%
-2.67dB to -3.37dB
±2%
-2.21 dB to -3.94dB
±5%
4.9 WIDE BAND NOISE CHECK
Set the filter for 25.6MHz, LP mode, OdB Input gain and 26dB Output gain .
Disconnect the sinewavc signal from the filter Input.
With the Fluke connected to the Output via a 50 ohm terminated cable, measure the wideband noise voltage
present.
Wideband noise should be <5mV which translates to SOO,uV referenced to the Input, since the net gain from
the filter Input to the meter is 2OdB.
4.10 STOPBAND ATTENUATION CHECK
NOTE: This test uses a SpeCll1lnl analyzer to detect the rejected signal. Most spectrum analyzers have a maximum
signal amplitude wuhout damage limu. Care should be taken {hat this signal level limit is not exceeded: A simple
precaution would be to use a 50 ohm inline 20dE attenuator at the analyzer Input. It is also advisable to set all the
equipm ent before connecting the analyzer.
Set the filler to the initial setting at the beginning of this Section.
Set the filler coupling to AC, cutoff frequency to 10kHz, and mode to GAIN.
Set the Tektronix 191 signal generator for IMHz, 3Vp-p into 50 ohms.
Connect the Tektronix 191 to the filler Input.
Sct the spectrum analyzer to measure the 3Vp-p, 1MHz signal into a 50 ohm termination at the filter Output
and connect the filter Output to the analyzer.
Adjust the analyzer for OdB, referencing level at the 1MHz signal.
Set the Filter [or LP mode.
The measured amount of 1MJ Iz signal should be down l00dB.
Set the signal generator for llJMHz.
The measured amount of lOMHz signal should be down 8OdB.
Set the signal generator for 30MlIz.
The measured amount of 30M Hz signal should be down 7OdB.
NOTE: Zero referencing ofthe spectrum analyzer at I OOMHz must be done by connecting the signal generator to
the spectrum analyzer Input.
Set the signal generator for lOOMHz.
The measured amount of l00MHz signal should be down 5OdB.
Model 35
Section 4 - Incoming Acceptance
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