31 October 1999
Source: Hardcopy from the National Security Agency received October 21, 1999.
Released in response to an
FOIA request dated
May 18, 1998. Of twenty-two TEMPEST-related documents requested, only parts
of two were released. NSA
wrote that most remain classified as SECRET and unreleasable. An
appeal for additional
releases has been filed.
This a fifth and final part of transcription of a 172-page document in which
classified sections, about half of the volume, have been redacted (indicated
by xxxxxxxx).
First part of transcription, Appendix A:
http://cryptome.org/jya/nstissam1-92a.htm
Second part, Table of Contents and Sections 1-5:
http://cryptome.org/jya/nt1-92-1-5.htm
Third part, Sections 6-12:
http://cryptome.org/jya/nt1-92-6-12.htm
Fourth part, Distribution List:
http://cryptome.org/jya/nt1-92-dist.htm
The other release, NSA/CSS Regulation 90-6, Technical Security Program,
a 12-page document:
http://cryptome.org/jya/nsa-reg90-6.htm
Classification symbols: (U) = unclassified, (C) = classified, FOUO = for
official use only. Overstrikes in the original.
For comprehensive TEMPEST stuff (non-secret, that is) see The Complete,
Unofficial TEMPEST Information Page:
http://www.eskimo.com/~joelm/tempest.html
From Table of
Contents
APPENDICES
A. CLASSIFICATION OF
COMPROMISING EMANATIONS INFORMATION (Separate file)
A.1 General
A.2 Scope
A.3 Rationale
A.4 Classification Marking
A.5 Foreign Release
A.6 Specific Guidelines
A.7 TEMPEST Classification Chart Outline
A.8 TEMPEST Classification Chart
B. DESCRIPTION OF
CORRELATED SIGNALS
C. TEST GUIDELINES
FOR PARALLEL INFORMATION TRANSFER EQUIPMENT
C.1 Purpose
C.2 Parallel Transfer Example
C.3 Types of Parallel Information Transfer
C.3.1 Return-to-Zero Signals
C.3.2 Nonreturn-to-Zero Signals
C.3.3 Polygraphic and Multiplexed Signals
C.4 Test Patterns
C.4.1 Type A Test Patterns
C.4.2 Type B Test Patterns
C.4.3 Type C Test Patterns
C.5 Emanation Measurement Procedures
C.6 Evaluation of Results
C.6.1 Bit Density
C.6.2 The Effect of Parity Check Bits
C.7 Effect of Multiple Signals
D. ALPHANUMERIC CRT
DISPLAYS
D.1 Scope
D.2 Introduction
D.3 Examples of Scanning and Character Generation Methods
D.3.1 Scanning
D.3.2 Character Generation
D.4 Examples of Defining Rd
D.4.1 Standard TV Display -- Continuous Scan
D.4.2 Dot Matrix -- Continuous Scan
D.4.3 Dot Matrix -- Modified Continuous Scan
D.4.4 Stroke or Vector Generation
D.5 Special Test Requirements
D.5.1 Alphanumeric CRT Displays
D.5.2 Bit Mapped Displays
E. AUTOMATED TESTING
SYSTEMS CERTIFICATION REQUIREMENTS
E.1 Purpose
E.1.2 [sic] Supplementary Manual Test
E.1.3 General Approach
E.1.4 System Certification Philosophy
E.1.5 Alternative Approaches
E.2 Automated Test Procedures
E.2.1 General
E.2.2 Tuning Scheme
E.2.3 Measurement Accuracy
E.2.4 Digital Voltmeter
E.2.5 Measurement Gate Time
E.2.6 Substitution Sources
E.3 Advance Certification Testing Requirements
E.3.1 Rd-Type Signal Certification Tests
E.3.2 Rd-Type Signal Certification Tests
E.4 Periodic Calibration Verification Requirements
E.4.1 Internal Attentuator Calibration Verification
E.4.2 Internal Source Verification
E.5 Scan Accuracy Verification Requirement
E.6 Automated Detection Systems Using A Spectrum Analyzer
E.6.1 Implementation
E.6.2 Automated Testing Procedures Using A Spectrum Analyzer
E.6.3 Advance Certification Testing Requirements
E.6.4 Rt-Type Signal Certification Tests
E.7 Critical Feature List Requirements
E.7.1 Critical Features List
E.8 Documentation Requirements
E.8.1 Test Instrument Certification
E.8.2 Test Plan Additions
E.8.3 Data Collection and Reporting
E.9 Security
F. DETECTION SYSTEM
BANDWIDTH MEASUREMENT
F.1 Introduction
F.2 6 dB Bandwidth Measurements: Tunable Heterodyne Detection System With
Demodulator
F.2.1 Signal Generator Requirements
F.2.2 Measurement Procedure
F.3 6 dB Bandwidth Measurements: Tunable Heterodyne or Tunable Non-Heterodyne
Detection System Without Demodulator
F.4 6 dB Bandwidth Measurements: Non-tunable Detection Systems
F.5 Impulse Bandwidth Measurements (IBW): Tunable Heterodyne Detection System
With Demodulator
F.6 Impulse Bandwidth. Measurements: Tunable Heterodyne or Tunable Non-Heterodyne
Detection System Without Demodulator
F.7 Impulse Bandwidth Measurements: Non-tunable Detection Systems
G. TABLES AND
FIGURES
H. LEVEL I LIMITS
I. LEVEL II LIMITS
J. LEVEL III LIMITS
K. IMPULSE GENERATOR
CALIBRATION
L. TEMPEST TEST PLAN
OUTLINE
M. TEMPEST PROFILE
Distribution List (Separate
file)
[Pages B-1 to B-10]
CONFIDENTIAL
DESCRIPTION OF CORRELATED SIGNALS
B.1. (U) The tester has the responsibility to describe clearly and
accurately any correlated signals detected during TEMPEST testing. Table
B-1 depicts the relationship between displayed emanations and types of
correlation. This table is not meant to be all-inclusive. Figures B-1 through
B-8 illustrate some examples of correlated emanations. The upper trace(s)
is teh monitor signal (i.e., RED signal) and the bottom trace(s) is the detected
signal. The photographs are representative of onlya few of the possilbe types
of correlation. Also, the photographs depict a high signal-to-noise ratio
to facilitate reproduction and to demonstrate easily recognizable correlation.
Under certain test conditions, the correlation may be far less obvious and
distinct.
Table B-1
ILLUSTRATION OF CORRELATED EMANATIONS (U)
[Table redacted.]
[Figure redacted.]
Figure B-1. -- Examples of Correlated Emanations. A-Scope Display
(U)
[Figure redacted.]
Figure B-2. -- Examples of Correlated Emanations. A-Scope Display
(U)
[Figure redacted.]
Figure B-3. -- Examples of Correlated Emanations. A-Scope Display
(U)
[Figure redacted.]
Figure B-4. -- Examples of Correlated Emanations. A-Scope Display
(U)
[Figure redacted.]
Figure B-5. -- Examples of Correlated Emanations. Raster Display
(U)
[Figure redacted.]
Figure B-6. -- Examples of Correlated Emanations. Raster Display
(U)
[Figure redacted.]
Figure B-7. -- Examples of Correlated Emanations. Raster Display
(U)
[Figure redacted.]
Figure B-8. -- Examples of Correlated Emanations. Raster Display
(U)
CONFIDENTIAL
[Pages C-1 to C-6]
CONFIDENTIAL
TEST GUIDELINES FOR PARALLEL INFORMATION TRANSFER EQUIPMENT
[Figure redacted.]
Figure C-1. -- Parallel Trasnfer of Data (U)
[Figure redacted.]
Figure C-2. -- Bit Density Emanation Examples (U)
[Ten lines redacted.]
___________________
1 NSTISSAM TEMPEST/2-91, "Compromising Emanations Analysis Handbook".
[Footnote to unknown passage.]
[Figure redacted.]
Figure C-3. -- Fingerprint Emanation Examples (U)
[Ten lines redacted.]
[Two full pages redacted.]
[Page C-6] THIS PAGE INTENTIONALLY BLANK
CONFIDENTIAL
[Pages D-1 to D-10]
CONFIDENTIAL
ALPHANUMERIC CRT DISPLAYS
D.1. (U) Scope. -- This appendix describes the operation of alphanumeric
CRT displays and presents guidelines for determining RED signaling rates.
D.2. (U) Introduction.
[Twenty lines redacted.]
D.2.3 (U) The determination of Rt is made in the same manner as described
in 5.5.2.
D.3. (U) Examples of Scanning and Character Generation Methods.
D.3.1 (U) Scanning.
D.3.1.1 (U) Video Scan: Continuous. -- In a continuous scan display, the
electron beam of the CRT starts at a given coordinate point and sequentially
moves through each coordinate point at a fixed sweep speed. This type of
scanning can be extended to other types of CRTs, such as a standard TV monitor
where the scanning is "interlaced" (see Figure D-1).
D.3.1.2 (U) Video Scan: Modified Continuous. -- The electron beam of the
CRT scans all the displayable points for each character of all character
positions. The pattern traced by the defiection system is normally a vertical
modulation of a herizontal sweep. This type of scan uses a sawtooth pattern
sometimes referred to as a "diddle pulse" sawtooth pattern (see Figure D-2).
D.3.1.3 (U) Random Scan. -- In a CRT display with this type of scan, the
beam is not scanned linearly, but is directed from any screen location to
any other.
D.3.2 (U) Characrer Generation.
D.3.2.1 (U) Standard TV Display. -- The individual characters are displayed
by unblanking the electron beam during line segments of a continuous scan
(see Figure D-3).
D.3.2.2 (U) Dot Matrix. -- The individual characters are displayed by unblanking
the electron beam at the appropriate positions in a dot matrix (see Figure
D-4).
D.3.2.3 (U) Stroke or Vector Generation. -- The individual characters are
displayed by "drawing" small line segments (vectors) to make up the character
(see Figure D-5). The program which is controlling the display must control
the electron beam position, as well as unblanking, since there is no raster.
D.3.2.4 (U) Beam Extrusion. -- The individual characters are displayed by
passing the electron beam through a selected shaped aperture in a metal plate
which causes the beam to assume the shape of the aperture when focused on
the face of the CRO.
D.4. (U) Examples of Defining Rd.
[Fifty lines redacted.]
D.5 (U) Special Test Requirements.
D.5.1 (U) Alphanumeric CRT Displays.
[Full page redacted.]
[Ten lines redacted of a, b, c and d.]
D.5.3 (U) The testing organization shall provide signalling characteristics
used to determine the Rd's and Rt's. Any deviations to the above test
requirements shall be documented and justified.
UNCLASSIFIED
[Pages E-1 to E-6]
UNCLASSIFIED
GUIDELINES FOR AUTOMATED TESTING AND INSTRUMENTATION
E.1 (U) Purpose. -- [Four lines redacted.]
E.1.1 (U) Supplementary Manual Test. -- [Six lines redacted.]
E.1.2 (U) Alternative Approaches. -- [Three lines redacted.]
E.2. (U) Automated Test Procedures.
E.2.1 (U) General. -- [Twelve lines redacted.]
E.2.2 (U) Prescan Calibration Procedures. -- [Four lines redacted.]
E.2.3 (U) Calibration Verification During Testing [Five lines redacted.]
E.3. (U) Automated Detection System Parameters.
[Twenty lines redacted.]
E.4. (U) Documentation Requirements. -- Documentation requirements
for automated testing are indicated below and in Paragraphs 6.3 and 8.4.
[Thirty-two lines redacted.]
[Full page and five lines redacted.]
[Page E-6] THIS PAGE IS INTENTIONALLY BLANK
UNCLASSIFIED
[Pages F-1 to F-4]
UNCLASSIFIED
DETECTION SYSTEM BANDWIDTH MEASUREMENT
F.1. (U) Introduction. -- The overall detection system bandwidth shall
be used when determining compliance of TEMPEST detection systems with the
bandwidth requirements of this document. Procedures are presented for measuring
sine wave and impulse bandwidths of non-tunable detection systems and tunable
detection systems with and without a Demodulator. Alternate procedures rnay
be used, provided the same results are obtained as when using the specified
procedures herein. The alternate procedures used must be documented in the
test instrumentation certification report and must be approved by the sponsoring
organization.
F.2. (U) 6 dB Bandwidth Measurements: Tunable Heterodyne Detection System
with Demodulator. -- This procedure is required for deterlIiining the
overall 6 dB detection system bandwidth of tunable heterodyne detection systems
at the post-detection output. This overall bandwidth is equal to the difference
between the low-pass and high-pass 6 dB cutoff frequencies, as measured using
F2.2.a through i below.
F.2.1 (U) Signal Generator Requirements. -- This procedure accounts for the
effect of both the IF and video circuits upon the overall low-pass cutoff
frequencies. An RF sine wave signal generator shall be used for the measurements.
The RF signal generator carrier frequency shall be tunable and shall be within
the tuned frequency range of the detection system. The RF generator carrier
signal shall be amplitude-modulated with a sine wave using any convenient
modulation index (e.g., 20 percent). The modulation index shall be maintained
constant during the measurement, unless otherwise noted. The frequency of
the modulating signal shall be adjustable over the modulating frequency
capability of the RF signal generator. If the maximum usable modulating frequency
is greater than the expected IF bandwidth, then only one RF signal generator
is required. If the expected IF bandwidth is greater than the maximum usable
modulating frequency, then two RF sine wave generators are required for the
test. The second RF generator shall be tunable over the same frequency range
as the first RF generator, but shall not be modulated. When two RF generators
are required, both generators must provide frequency accuracy and resolution
which are at least one order of magnitude better than the expected overall
bandwidth.
F.2.2 (U) Measurement Procedure. -- The overall bandwidth shall be measured
as follows:
a. (U) If one RF signal generator is required, apply the output of the generator
directly to the input of the detection system. If two RF signal generators
are required, apply both generators through a power divider to the input
of the detection system. Inline attenuation (e.g., 20 dB) may be used as
needed to provide signal attenuation and signal generator isolation. Initially,
decrease the output of the second generator (if used) to zero or at least
40 dB below the output of the modulated RF generator.
b. (U) Adjust the carrier frequency of the modulated RF generator around
the tuned center frequency of the detection system until the maximum level
of the modulating signal is observed at the same output port of the detection
system as used during TEMPEST testing. The level of the modulated carrier
signal applied to the detection system and the modulation index must be such
that the detection system output signal is at or below the 1 dB compression
Doint.
c. (U) Adjust the frequency of the modulating signal until the rnaximum output
level of the detection system is observed or the maximum available modulating
frequency has been reached, whichever comes first. Readjust the RF signal
generator level, if necessary, to maintain the detection system output level
at or below the 1 dB compression point. Note the modulating frequency and
the detection system output level as a reference.
d. (U) Maintaining the same RF generator carrier frequency, as in c
above, reduce the frequency of the modulating signal until the output of
the detection system decreases 6 dB from the reference level noted in
c above or until the modulating frequency is essentially zero frequency
(such as would occur in d.c.coupled Demodulator), whichever comes first.
Record this frequency as the 6 dB high-pass cutoff frequency.
e. (U) Increase the modulating frequency found in step d as necessary
to produce a relatively noise free detection system output signal, but do
not increase the modulating frequency to more than 10 percent of the overall
bandwidth. Note the resulting modulating frequency and the detection system
output level as a reference. Shift the RF carrier frequency down until the
output of the detection system decreases 6 dB from the reference level of
this step. Increase the RF generator carrier level by 6 dB and decrease the
modulation index by 6 dB (e.g., to 15 percent).
f. (U) If only one RF signal generator is required, then increase the frequency
of the modulating signal until the maximum output level of the detection
system is observed. Note the new output reference level. Then, continue to
increase the modulating frequency until the detection system output level
decreases 6 dB from the new reference level. Record the resulting modulating
frequency as the overall 6 dB low-pass frequency.
g. (U) If two RF signal generators are required, set the frequency of the
second generator equal to the first generator, plus the reference modulating
frequency of step e. Turn off the modulation of the first generator.
Increase the level of the second generator until the detection system output
equals the reference level of step c minus 6 dB. Next, increase the
frequency of the second RF generator until the maximum output level of the
detection system is observed. Note this output level as the new reference
level. Then continue to increase the frequency of the second RF generator
until the detection system output level decreases 6 dB from the new reference
level. Record the resulting difference between the two RF generator frequencies
as the overall 6 dB low-pass cutoff frequency.
h. (U) Subtract the result of d (above) from that of f or
g (above) to obtain the overall 6 dB detection system bandwidth.
i. (U) Repeat the bandwidth measurements at a minimum of two tuned frequencies
per decade or one near the center of each tuning band of the detection system,
whichever is the greater number of readings.
F.3. (U) 6 dB Bandwidth Measurements: Tanable Heterodyne or Tunable
Non-Heterodyne Detection System Without Demodulator. -- The bandwidth
of these detection systems shall be mensured as follows:
a. (U) Apply the output of a calibrated unmodulated sine wave
generator1 to the input of the detection system.
b. (U) Adjust the carrier frequency of the cw generator around the center
frequency of the detection systern until the maximum output level of the
detection system is observed at the same port used during TEMPEST testing.
Note the output level.
c. (U) Maintaining the same cw generator carrier amplitude and detection
system tuned center frequency as in b (above), reduce the cw generator
carrier frequency until the output level of the detection system decreases
6 dB from the level obtained in b (above), or until the carrier frequency
is essentially zero frequency (such as would occur at a detection system
output with d.c. response), whichever comes first. Note this frequency.
d. (U) Repeat c (above), except increase the carrier frequency until
the output level decreases 6 dB from the level obtained in b (above).
Note this frequency.
e. (U) Subtract the frequency recorded in c (above) from that in
d (above) to obtain the detection system bandwidth.
f (U) Repeat the bandwidth measurements at a minimum of two frequencies per
decade or one per tuning band (near the center), whichever is the greater
number of readings.
___________________
1 A swept-frequency generator with a constant output voltage may be
used in lieu of the manually-tuned generator. Using a calibrated display
device, the detection system bandwidth can then be read directly.
F.4. (U) 6 dB Bandwidth Measurements: Non-Tunable Detection Systems.
-- The 6 dB bandwidth on non-tunable detection systems shall be measured
in accordance with the procedures specified in Paragraph F.3. The measurement
shall be made on the entire composite detection system, including the
transducer2 (antenna, voltage or current probe, etc.) and display
device (CRO, strip chart recorder, etc.), unless it can be shown that the
bandwidth of these devices will not restrict the bandwidth of the remainder
of the detection system.
_________________
2 The bandwidth of some transducers (e.g., antennas, current probes)
is very difficult or impractical to measure. In these cases, bandwidth
measurements need not be made ou the device, but precautions shall be taken
to assure that lhe device does not limit the overall detection system
bandwidth.
F.5. (U) Impulse Bandwidth Measurements (IBW): Tunable Heterodyne Detection
System with Demodulator. -- The impulse bandwidth of these detection
systems shall be measured as follows:
a. (U) Apply the output of a calibrated AM sine wave generator to the input
of the detection system. The generator output signal shall be amplitude-modulated
30 percent with a sine wave of suitable freauency.
b. (U) Adjust the carrier frequency of the AM sine wave generator around
the center frequency of the detection system until the maximum output level
of the detected signal is observed at the same output port of the detection
system used during TEMPEST testing. Note the output peak-to-peak amplitude
observed on the oscilloscope and the signal level in rms volts of the AM
sine wave applied at the input of the detection system.
c. (U) Disconnect the AM sine wave generator and apply the output of a calibrated
impulse generator to the input of the detection system. Set the IG repetition
rate to any convenient rate less than one-fifth of the nominal overall detection
system bandwidth.
d. (U) Adjust the IG output level so that the peak magnitude of the waveform
displayed on the oscilloscope (at the detection system output) is equal to
one-half the peak-to-peak amplitude of the detected sine wave recorded in
b (above). Note the level in volts (equivalent rms sine wave)/MHz
of the impulsive signal applied at the input of the detection system.
e. (U) Calculate the impulse bandwidth of the detection system with the following
formula:
|
|
0.3 (AM sine wave input signal level in rms volts recorded in b (above).) |
| IBW |
= |
__________________________________________________________________ |
|
|
(impulsive input signal level in volts (equivalent rms sine wave)/MHz, recorded
in d (above).) |
f. (U) Repeat the impulse bandwidth measurements at a minimum of two tuned
frequencies per decade or one per tuning band (near the center), whichever
is the greater number of readings.
F.6. (U) Impulse Bandwidth Measurements: Tunable Heterodyne or Tunable
Non-Heterodyne Detection System Without Demodulator. -- The impulse bandwidth
of these detection systems shall be measured as follows:
a. (U) Apply the output of a calibrated unmodulated sine wave generator to
the input of the detection system.
b. (U) Adjust the carrier frequency of the cw generator around the center
frequency of the detection system until the maximum output level of the detection
system is observed on an oscilloscope at the same port used during TEMPEST
testing. Note the output peak-to-peak amplitude observed on the oscilloscope.
and the signal level in rms volts of the cw sine wave applied at the input
of the detection system.
c. (U) Disconnect the cw generator and apply the output of a calibrated impulse
generator to the input of the detection system. Set the IG repetition rate
to any convenient rate less than one-fifth of the nominal overall detection
system bandwidth.
d (U) Adjust the IG output level so that the peak-to-peak waveform displayed
on the oscilloscope (at the output of the detection system) is equal to the
peak-to-peak amplitude of the cw waveform recorded in b (above). Note
the level (in volts (equivalent rms sine wave)/MHz) of the impulsive signal
applied at the input of the detection system.
e. (U) Calculate the impulse bandwidth of the detection system with the following
formula:
|
|
(Sine wave input signal level in rms volts recorded in b (above).) |
| IBW |
= |
__________________________________________________________________ |
|
|
(impulsive input signal level in volts (equivalent rms sine wave)/MHz, recorded
in d (above).) |
f. (U) Repeat the impulse bandwidth measurements at a minimum of two tuned
frequencies per decade or one per tuning band (near the center), whichever
is the greater number of readings.
F.7. (U) Impulse Bandwidth Measurements: Non-Tunable Detection Systems.
-- The impulse bandwidth shall be measured as follows:
a. (U) Apply the output of a calibrated unmodulated sine wave generator to
the input of the detection system.
b. (U) Adjust the carrier frequency of the cw generator around the center
frequency of the detection system passband.
c (U) Obtain a convenient display of the detection system output signal on
an oscilloscope. Note the output peak-to-peak arnplitude observed on the
oscilloscope and the signal level in rms volts of the cw sine wave applied
at the input of the detection system.
d. (U) Disconnect the cw generator and apply the output of a calibrated impulse
generator to the input of the detection system. Set the IG repetition rate
to any convenient rate less than one-fifth of the nominal overall detection
system bandwidth.
e. (U) Adjust the IG output level so that the peak magnitude of the waveform
displayed on the oscilloscope (at the output of the detection system) is
equal to one-half the peak-to-peak amplitude of the cw waveforrn recorded
in c above. Note the level, in volts (equivalent rms sine wave)/MHz,
of the impulsive signal applied at the input of the detection system.
g. (U) Calculate the impulse bandwidth of the detection system with the following
formula:
|
|
(Sine wave input signal level in rms volts, recorded in c (above).) |
| IBW |
= |
__________________________________________________________________ |
|
|
(impulsive input signal level in volts (equivalent rms sine wave)/MHz, recorded
in d (above).) |
UNCLASSIFIED
[Pages G-1 to G-12]
CONFIDENTIAL
TABLES AND FIGURES
[Full page of two boxes redacted.]
[Full page of two boxes redacted.]
[Half page with one box redacted.]
Note: See Table G-6 for application examples [Note to unknown table.]
[Full page with one box redacted.]
_________________
1 Lowest bit rate as defined in paragraph 3.1.4
2 Refer to Table G-5. [Footnotes to unknown figures.]
[Figure redacted.]
Figure G-1. -- Assumed Transition Time Based on Pulse Width Signaling
Rate (Maximum) (U)
[Figure redacted.]
Figure G-2. -- Bounds on Tunable Overall Detection System Bandwidth
(U)
[Figure redacted.]
Figure G-3. -- Maximum Permissible Tunable Starting Test Frequency (U)
Note: This figure is equivalent to Figure 10-1.
UNCLASSIFIED
Figure G-4. -- Typical Test Instrumentation for ER Tests (U)
Note: This figure is equivalent to Figure 10-2.
UNCLASSIFIED
Figure G-5. -- Required Minimum Antenna Distances From Metal Surfaces
and Objects Other Than the EUT (U)
[Page G-12 - Full page redacted.]
CONFIDENTIAL
[Pages H-1 to H-18]
UNCLASSIFIED
LEVEL I
LIMITS
[All pages redacted.]
UNCLASSIFIED
[Pages I-1 to I-8]
UNCLASSIFIED
LEVEL II
LIMITS
[All pages redacted.]
UNCLASSIFIED
[Pages J-1 to J-4]
UNCLASSIFIED
LEVEL III
LIMITS
[All pages redacted.]
UNCLASSIFIED
[Pages K-1 to K-2]
UNCLASSIFIED
IMPULSE GENERATOR CALIBRATION
K.1. (U) Procedure. -- Impulse generators shall be calibrated by one
of the four following methods:1
___________________
1 Other methods may be used if justified and approved by the sponsoring
organization.
K.1.1 (U) Method 1.
a. (U) Apply the output of the impulse generator to be calibrated to the
input of an amplitude-linear receiver having synchronously tuned, less-than
critically-coupled, circuits. Radio interference field intensity receivers
are satisfactory for this purpose if their impulse bandwidth is`at least
five times the repetition rate of the impulse generator. Any automatic gain
control (AGC) system shall be defeated. Once the receiver controls are set,
they should not be changed during the calibration process.
b. (U) Obtain an oscilloscope pattern of the overall receiver response at
the IF output. The oscilloscope controls shall be so adjusted that the pattern
is as large as possible within the calibrated area on the face plate. Either
photograph or trace the pattern. Record the oscilloscope sweep speed setting.
(The sweep speed shall be calibrated accurately.)
c. (U) Use a planimeter or other integrating device to determine the area
of the positive portion of the major lobe of the response waveform. (More
accuracy can be obtained by summing the area under the odd-numbered lobes
and subtracting from it the total area under the even-numbered lobes.) This
operation shall be carried out at least five times and the average of the
readings taken as the area.
d. (U) Calculate the impulse bandwidth of the receiver in accordance with
the following formula:
|
|
pattern height* in cm |
|
| IBW in MHz |
= |
_____________________________________ |
X 10-6 |
|
|
(pattern area* in cm2 (sweep speed in sec/cm) |
|
*Refers only to positive portion of response waveform.
e. (U) Connect a calibrated sine wave generator to the receiver. Tune the
generator to the receiver's tuned frequency and adjust the output until the
peak pattern height is the same as that obtained with the impulse generator
in a. and b. (above). Record the output of the sine v;ave generator
in microvolts (rms).
f. (U) Calculate 20log10(e/d) where e and d are the
results obtained in e. and d. (above) expressed in microvolts
(rms) and megahertz, respectively. This calculation gives the spectral intensity
of the impulse generator output in dB,µV/MHz (equivalent rms
sine wave).
K.1.2 (U) Method 2.
a. (U) Select a bandpass or low-pass filter with the following characteristics:
(1) (U) Minimum upper roll-off of 18 dB/octave.
(2) (U) Maximum upper 3 dB cutoff point which is 10% of the reciprocal of
the expected width of the driving impulse (from the IG to be calibrated)
or 80% of the bandpass of the CRO in use, whichever is less.
(3) (U) Passband wide enough to permit passage of sufficient energy such
that the peak voltage of the output waveform can be accurately read on the
CRO.
(4) (U) 50 ohm input and output impedance in the passband.
b. (U) Determine thc impulse bandwidth (IBW) of the filter empioying the
procedures specified in method 1, paragraphs a. through d.
(above), substituting the word "filter" for "receiver". Once the IBW of the
filter has becn measured, the filter may be used to calibrate any number
of IGs; however, the IBW shall be rechecked in accordance with the calibration
requirements specified in Paragraph 7.6.
c. (U) Terrninate the output of the IG to be calibrated with a 6 dB (minimum),
50 ohm pad and connect it to the input of the filter.
d. (U) Terminate the output of the filter with a 50 ohm resistive load and
connect it to the vertical input of the CRO.
e. (U) Record the peak voltage of the filter output on the CRO microvolts.
f. (U) Calculate:
20log10(e/b) + pad loss - 3 dB + filter insertion loss
where e and b are the results obtained in paragraphs e. and b.
(above), expressed in microvolts (peak) and megahertz respectively. This
calculation gives the spectral intensity of the impulse generator output
in dB,µV/MHz (equivalent rms sine wave).
K.1.3 (U) Method 3. -- Compare the output of the IG to be calibrated, with
the output of another IG which has previously been calibrated, in accordance
with method 1 or method 2, within the last six months.
K.1.4 (U) Method 4.
a. (U) Apply the output of the impulse generator to be calibrated to the
input of a spectrum analyzer having the following characterstics:
(1) (U) Known impulse bandwidths.
(2) (U) Absolute amplitude accuracy equal to +/-2 dB or better.
b. (U) Select a spectrum analyzer bandwidth at least five times the repetiton
rate of the impulse generator, but no larger than one-tenth the usable spectrum
of the impulse generator. Select a scan time in seconds/division, no less
than 10/repetition rate (Hz) to insure ten-impulse responses per division.
c. (U) Add any conversion factors to the spectrum analyzer displayed voltage
needed to convert dBm to dB ref. 1 µV rms. Subtract the impulse
bandwidth of the spectrum analyzer in dB ref. 1 MHz from this value to convert
to dB ref. 1 µV/MHz and subtract 3 dB to convert the reading
to dBµV/MHz (equivalent rms sine wave), which is the spectral
intensity of the impulse generator output.
UNCLASSIFIED
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