United States
Environmental Protection
Agency
Office of Radiation Programs
Nonionizing Radiation iranch
P.O. Box 18416
Las Vegas NV 89114-8416
EPA-520/6-85-019
June 1985
Radiation
xvEPA
Development of
a System to Measure
the Response Time of
Microwave Survey
Instruments to
Rotating Radar
Antenna Patterns
i
-------
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Development of a System to Measure the Response Time
of
Microwave Survey Instruments to Rotating Radar Antenna Patterns
by
Paul A, Monheiser
May 1982
U.S. Environmental Protection Agency
Nonionizing Radiation Branch
Office of Radiation Programs
P.O. Box 18416
Las Vegas, NV 89114-8416
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DISCLAIMER
Although the work described in this document has been funded wholly by the
United States Environmental Protection Agency it has not been subjected to the
Agency's required peer and policy review and therefore does not necessarily
reflect the views of the Agency. No Official endorsement should be inferred.
-------
Acknowledgments
The author of this report would like to acknowledge the assistance
provided by the following people:
Richard A. Tell, Physicial Scientist, Acting Branch Chief, NRSB, U.S.
Environmental Protection Agency
Paul C. Gailey, Evnironmental Scientist, NRSB, U.S. Environmental
Protection Agency
Edwin D. Mantiply, Physical Scientist, NRSB, U.S. Environmental
Protection Agency
Michael Molony, Computer Programmer, Computer Sciences Corporation
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Abstract
The Nonionizing Radiation Surveillance Branch of the U.S. Environmental
Protection Agency conducts a program to assess environmental exposure levels
of radiofrequency fields and to develop Federal regulatory guides to limit the
exposure of the population to radiofrequency fields. An essential element of
this program is the maintenance of an electromagnetic field measurement and
instrumentation calibration capability. This report describes a project which
developed a laboratory method for evaluating the response characteristics of
microwave survey instruments used for assessing microwave exposure hazards.
This project involved the development of a system for simulating, in a
controlled fashion, the time varying microwave fields that would be present
around a high-power radar antenna which rotates. A suitable synthesis of such
fields provides a convenient and accurate way to evaluate the response time of
survey instruments and therefore establish uncertainty limits for instrument
readings obtained in similar environments.
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Table of Contents
Page
Purpose of Project ................. . 1
General Considerations for Radar Patterns Synthesis 5
Alternative I.. 7
Alternative II 9
TWT Noise Reduction. 13
Determination of System Transfer Function. . . 20
Data Collection at McCarran Airport. .... 23
Controlling Computer Program 34
Data Transfer Between Systems. .... ............ 35
Procedure for Punching Data from HP9845B .... 44
System Set-up in Anechoic Range. ...... .... 45
Radar Signal Simulation 51
Time Response of the NARDA 8616 Electromagnetic Monitor 55
Summary. 61
List of Abbreviations. 62
References 63
Appendix I . Al
Appendix II A2
Appendix III............. ........... A3
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Purpose of Project
One of the functions of the Nonionlzing Radiation Surveillance Branch
(NRSB) of the U.S. Environmental Protection Agency is the measurement of
Intense electromagnetic fields which are radiated from a variety of sources.
Common sources of electromagnetic radiation are radars. The NRSB is concerned
with measurement techniques and the type of equipment best used for accurate
determination of possibly hazardous electromagnetic fields. One method for
measuring such fields is the use of broadband radiation monitors. Such
devices measure the intensity of electromagnetic fields over a very wide range
of frequency.
The best way to look at a radar signal is by using a spectrum analyzer.
By examining a radar signal with a spectrum analyzer, all the important
properties of the signal can be measured. Some of these properties are the
pulse width, occupied bandwidth, duty cycle, peak and average power, and if
the radar antenna is rotating, the apparent radiation pattern of the radar's
antenna including the speed of rotation. Knowledge of all these properties of
the signal may be necessary for certain analyses, but are not necessary for
determining the field strength. Spectrum analyzers are very expensive and not
suitable for "mapping out" field strength values over extensive areas since it
is very cumbersome and requires AC power. A spectrum analyzer is also a
complicated piece of equipment to operate and requires trained personnel to
interpret the results. If only the field intensity of the signal is of
interest it may be feasible to use a broadband radiation monitor (BRM) instead
of a spectrum analyzer.
A broadband radiation monitor is an instrument which may be hand-held and
operated from its own power source. Such a device usually outputs an analog
signal indicating the power density or field strength of any field it is
exposed to in its frequency range.
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It may be feasible to use a BRM for rotating radar signals, although this
can place severe constraints on the accuracy of the indicated field intensity
depending on the beam width and rotational speed of the radar antenna. The
purpose of this project is to evaluate the suitability of using a BRM such as
the NARDA 8616 Electromagnetic Radiation Monitor with probe model 8621 for
field intensity measurements of rotating radar antenna signals.
It is inconvenient to use a real radar signal for testing of the BRM since
access to the required strong signals would most likely require the testing to
be performed outdoors near a radar installation. To eliminate this problem,
the major emphasis of this project is to synthesize a rotating radar signal
pattern for use in the laboratory.
By creating a signal that closely resembles the signal emitted by a
rotating radar antenna, the testing of a BRM may be performed in the
laboratory under controlled conditions. Also, the parameters of the signal
may be changed to facilitate further exploration of the instrument's
response. The parameters which need to be capable of change are (1) the
rotational duty cycle, (2) the carrier frequency, and (3) the intensity of
the field.
The major concern is how the BRM responds to the radiation pattern created
when a radar antenna rotates. If a radar antenna is not rotating, there is no
problem in using a BRi»l. The analog reading will correspond to the power
density of the field assuming the BRM has been properly calibrated. Any
person or object occupying that particular location will be exposed to that
particular power density. It is not so easy, however, to determine what power
density one is exposed to if the antenna is rotating* The rotation of the
antenna creates a continuously varying field intensity level. Using a BRM,
one could take two values of data; the peak intensity observed and some lower
value when the radar antenna is swung away from the instrument. The concern
of this project is to determine how these readings may be used to compute the
average power density; i.e., the power density as averaged over a complete
rotation of the radar's antenna. The peak reading observed may not be the
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actual peak signal of the antenna. A slow time response of the BRM could
cause a low peak reading. Using the synthesized radar signal in the
laboratory, the response of the BRM may be observed under controlled
conditions to determine if the time response truly presents a problem, and
such a determination forms the crux of this project.
The most commonly used BRM in the microwave frequency range suitable for
radar applications is the Narda 8616 Electromagnetic Radiation Monitor. The
Narda high frequency probe Model 8621 (300 MHz to 26 SHz) uses thin-film
thermocouples that provide true square-law response, i.e., their voltage
output is linear with absorbed power. The probe contains three elements which
are mutually perpendicular to each other in an x-y-z axes fashion, as shown in
Figure 1. The summation of the DC signals from these three elements provide a
measure of the total power density independent of the polarization of the RF
signals. Since thermocouples are used, the average power density affects the
output, thus it is not necessary to include pulses in the synthesized radar
pattern as would be present in the actual radar's signal.
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5 cm Dia 1
Sphere '
Figure 1.
Relationship of the three mutually orthogonal probe elements of a NARDA 8621
high frequency probe.
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General Considerations for Radar Pattern Synrresis
In order to model a synthesized rotating radar par^rn after a real
pattern, it is necessary to collect data from ar operating radar
Installation. Using sophisticated NRSB equipment such EZ a Hewlett-Packard
8566A spectrum analyzer interfaced with a Hewlett-Packard 18458 computer, the
pattern of a rotating radar antenna may be stored in a nums*ical array and the
CRT display of the 8566A may be reproduced onto paptr thrnigh the use of the
graphics capability of the computer. An example of a ro-iting radar antenna
pattern obtained by this system is shown in Figure 2.
In order to synthesize the radar pattern, a carrier si oral must somehow be
amplitude modulated in such a way as to mimic the variation of the radiated
signal amplitude as the radar antenna rotates. This may is accomplished by
attenuating the carrier amplitude of a continuous wave (Ct) generator as to
simulate the actual variation in field intensity of the simal from a rotating
radar antenna pattern. This synthesized signal will be inplitude modulated
but will not be pulsed.
Since the attenuation must be rapidly changed to simulate the rapidly
varying radar signal and must be reproducible, the use if a computer for
instrumentation control is implied.
The carrier frequency should be in the range of 1 GHz ~o 10 GHz in order
to simulate the carrier frequency of radar but need not M the same as the
actual radar frequency since the BRM is sensitive to frequercy between 300 MHz
to 26 GHz.
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ANTENNA ROTATIONAL 1>1_ITY CYCLE
Operator --tichael R Moleirp
location LAB, EPA ROOM 521, BLDC C
SMC*? Tinr * 20
R»f»r»nce ~*v*l » 0 dBn
Seal* Div = to dB/
Ant*nna Rrrational Duty Cycle
Peak* ne*str*d at:
n 1. 220 -16.60dB*
Radar Rot. -ion
Sttctmrs/Rotation •. 12.14
93/23/81. 2.51 PH
R*m BU * 3 MHz
C«nt*r frcq » 1.3311 GHz
Location 2-. 82? -ii.90dB«
R P « 4.942
Main B*an ?»f»r»nc« -16.747 dB*
Antenna cU.~s> cycle ^ -20 SSI dBn
-18
-ea
u
pa
-3
d
5
* K rv
X — S T
C W ffi IV
a. I
£ BC it. U
2 7 ft - S
t S u £ at
g O OQ "* U.
K - C *- U
fr j t CE
•• *• 2.
|Sic
• SE*
5™ n.
D
r
CE
Ul
y —
C
-70
f—I—1—I
Tin* (seconds)
Figure 2.
Example of i rotating radar antenna pattern obtained from NRS8 measurement
system.
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Alternative I
One alternative considered for use in synthesizing a rotating radar
antenna signal pattern was to use a HP model 8620C sweep oscillator which may
have its signal level varied by applying a DC voltage to the external
amplitude modulation (AM) jack. A quickly changing DC voltage may then be
generated by using a computer interfaced to a Digital-to-Analog Converter
(OAC). A numerical array representing the required signal levels may be
stored in the computer memory and when output to the DAC under program
control, will provide the necessary amplitude modulation of the signal
corresponding to the radar antenna pattern. This system is illustrated in
Figure 3.
In order to test this system, a series of direct current (DC) voltages
were applied to the External Amplitude Modulation (EXT. AM) jack located at
the rear of the Hewlett-Packard (HP) 8620C sweep oscillator (see Figure 3).
For each DC voltage applied, the corresponding power output to the power meter
was recorded. These data were then fit to a curve in order to determine the
mathematical function of voltage versus power. In order to test the
reproducibility of this function, a randomly selected voltage was applied to
the EXT. AM jack of the HP 8620C to observe if the predicted power would be
output to the power meter. The power output was dramatically different from
the predicted power. The error was in the order of 3 d8. The original
voltages were then again applied to the system but the power output was not
the same as it was originally.
After much experimentation, it was observed that the HP 8620C signal
generator drifted in frequency. With this change in frequency the signal
generator changed its output power, especially when lower powers were
required. The frequency drift was too rapid to periodically check and
correct. After other techniques were tried to compensate for the frequency
drift, the use of the HP 8620C signal generator was considered impractical
since a rapid amplitude modulation of the signal is required. Therefore,
Alternative I was rejected for use in simulating a rotating radar antenna
signal pattern.
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HP 436 A
Power
Meter
{
DAC From
Varian
Computer
2oaxifi
Cable
/
il
HP 8620 C
Sweep
Oscillator
10 dB
Step
At ten.
Helia*
Cable
Forward
Power,.
^A
Hughes
1277 H
Traveling
Wave Tube
Amplifier
>JL 50 Q
f| Termination
Bi-Directionai
Coupler
NARDA 3024
^^^^^4
.
Radiated
Signal
EXT AM
Jack
Amplitude
Modulated
6 GHZ
Output
NARDA
Standard
Alternative I system.
antenna pattern.
Figure 3.
This system was considered but not used for simulating a rotating radar
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Alternative II
A second alternative considered for use in synthesizing a rotating radar
antenna signal pattern is to use a positive-intrinsic-negative (PIN) diode
modulator. This system is shown in Figure 4 and may allow a pulsed signal to
be output from the HP 8620C sweep oscillator if desired.
This alternative was not initially feasible since a PIN modulator was not
available to the Nonionizing Radiation Surveillance Branch (NRSB) of the
Environmental Protection Agency (EPA) at the conception of this project.
Since that time, however, a HP 8733B PIN modulator has been purchased by
NRSB. The specifications for this modulator are shown in Table 1, and its
dimensions are shown in Figure 5.
The function of the PIN modulator is to amplitude modulate the signal
produced by the signal generator (refer to Figure 4). The amplitude
modulation is controlled by applying a DC voltage as the bias to the bias port
of the PIN. The DC voltage causes the PIN to attenuate the signal through
it. A greater negative voltage applied to the bias results in a greater
attenuation of the signal through the PIN. The DC voltage which is applied to
the bias may be controlled by a computer. The computer outputs voltage from a
Digital-to-Analog-Converter (DAC). This allows a very rapid change of
voltages and therefore a rapid amplitude modulation of the signal since it
will be controlled by the computer.
The first test performed on the PIN modulator was to simply determine if
power out of the PIN for a given voltage into the bias was repeatable. A
constant 10 dBm signal was output from a signal generator at 6 GHz (see Figure
6 for test set-up). The PIN modulator was attached to the signal generator
and the power out of the PIN modulator was measured with a power meter as the
DC voltage to the bias was changed. The DC voltage was supplied by a DC power
supply and was monitored by a voltmeter at the bias. These sets of data were
then taken several times and the results were reproducible within *0.3 dB down
to 30 dB of attenuation. Data for this test were not taken below 30 dB of
attenuation because of the power detection limits of the HP 436A power meter.
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DC Voltage
to Bias.
HP 8733B
PIN Modulator
10 dB
Attenuator,
HP 360 D
Low Pass
Fifter
rf Signal
cw @ 4.1 GHZ
Heliax
Cable
Radiated
Signal
son
Termination
. 5?
NARDA 3024
Coaxial Coupler
Heliax
Cable
NARDA
643
Standard
Gain
Horn
Anechoic
Material
Figure 4.
System to synthesize an amplitude modulated signal simulating a rotating radar antenna pattern
using a PIN diode modulator.
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IfaMt L Specification*
ITS3A
tr«A
•TUB
tTJ4A
•ma
trssA
rr*4p*ncy Mugs (GHm)
fferaaaic foaf* (49
feMftte LOM (A1
I»X
IMti
Hialarum Input fanr.
ftMkorCWCvutta)1
It
U
U
I
rornrt Bfptnp*
Jtwtaanca (i ~
RT Cc«\n*ctor Tyy*
»«l«te «tal
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s
u
u
SJ
t
tat
1.1-4.1
It
<4.0« 4.0 to 4.1 CHt
nlbtata
t> At«ttHuida(iI«*
-------
@
6 GHZ
cw
HP 8620 C
Sweep
Oscillator
+ Q
Heliax
Cable
s
DC Bias
HP 8733 B
PIN Modulator
/<
h
r
1
HP 436 A
Power
Meter
Voltmeter]
{Ammeter I
Q
•»
DC
Power
Supply
Figure 6.
Initial test of the PIN Modulator.
12
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TWT Noise Reduction
Since the PIN modulator was performing satisfactorily, the Hughes 1277H
traveling wave tube (TWT) amplifier was added to the system to determine a
preliminary function of power out of the system versus voltage into the bias.
The equipment set-up for this test is illustrated in Figure 7.
10 dBm
4.5 GHZ
HP 8620 C
Sweep
Oscillator
HP 8733 B
PIN Modulator
DC Bias
Heliax
Cable
Hughes
1277 H
TWT
Amplifier
Attenuator
HP 436 A
Power
Meter
DC
Power
Supply
Figure 7.
Test of system with TWT.
13
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The results of this test revealed a disturbing problem. The noise level
of the TWT allowed only a small dynamic range of power levels. The data from
this test may be seen in Table 2. It is observed that from -0.82 volts DC to
-0.88 volts the power out of the TWT changed very little compared to the power
changes from -0.55 to -0.78 volts. When the input to the TWT was removed, the
output power was approximately -34 dim.
Table 2. TUT Dynamic Range Test
Voltage Applied
to PIN Bias
-0.55 (Volts)
-O.S7
-0.59
-0.60
-0.62
-0.64
-0.66
-0.68
-0.70
-0.72
-0.74
-0.76
-0.78
-0.80
-0.82
-0.84
-0.86
-0.88
-0.88
Power Out of
41dB Attenuator
+5.1 (dBmJ
44.3
+2.6
+1.6
-0.7
-3.5
-6.7
-10.0
-13.6
-17.1
-20.7
-24.0
-27.1
-2§.6
-31.4 1
-32.6 I Si
-33.3 > f
-33.6 1
-34.2 '
Small change due to noise
from TWT amplifier
Input to TWT disconnected
The useful dynamic range of approximately 35 dB was considered as an
unacceptable range for use in simulating a rotating radar antenna signal.
The first step to solving the problem of the TWT noise was to actually
look at the noise output using a HP 8655A spectrum analyzer. The input of the
TWT was terminated and a 10 dB attenuator attached to a 10 ft. piece of Heliax
cable was connected from the output of the TWT to the input of the spectrum
analyzer. The noise level of the TWT Is shown in Figure 8. This figure was
reproduced onto paper through the graphics capability of an HP 98458 computer
which interfaces with the HP 8655A spectrum analyzer.
14
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. 10/29/81. 4;23 PM
REF 0.0 dBm RTTEN 10 dB
10 dB/
POS PK
<
J5TflRT.-2-0.-GHz
.}"" RES BN 3 NHz
Vs
-Vf
-t?
-V
VBM 3 MH
STOP 12.3 GHz
SWp 250 m*9o
Figure 8
TMT noise from 2.0 to 12.0 SHz,
Since the frequency being used for the simulation was J^fbHz, it was
determined that a bandpass filter of 4 to 6 GHz would significantly reduce the
noise from the TWT. A HP 8432A bandpass filter was tested to determine its
true filtering capabilities. "Oiis test was performed using the equipment
Illustrated in Figure 9. The HP 8620C sweep oscillator was set up to sweep in
frequency from 2.0 GHz to 8.0 GHz. The HP 8566A spectrum analyzer was set up
to save and display only maximum values at each frequency point (max hold
function). The result of this test is shown in Figure 10. It can be seen that
the HP 8432A filter resulted in a band pass of approximately 3.86 to 6.2 GHz.
This significantly reduces the noise from below 3.3 GHz, but there is still
much noise allowed to pass above toe operating frequency of 4.5 GHz. In order
15
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2.0
HP 8620 C
Sweep
Oscillator
to 8
9 ^ '
.oc
5HZ
HP 8432 A
Band Pass
Filter
GU
~" """p
Max. Hold
on
Display
HP 8566 A
Spectrum
Analyzer
Figure 9.
Test of HP8432A bandpass filter.
to reduce the bandpass frequency range, a HP 360D low pass filter with a
cut-off frequency of 4.1 GHz was put in series with the bandpass filter. The
characteristics of the two filters in series was determined by the same method
illustrated in Figure 9, except both filters were connected together in
series. The results are shown in Figure 11. These results show that 4.5 GHz
can no longer be used for an operating frequency since it is filtered by the
low pass filter. A closer look at the filter characteristics revealed a low
standing wave ratio (SWR) at 4.1 GHz. Therefore, since all the equipment used
in the system is capable of operation at this frequency, 4.1 SHz became the
new operating frequency for future testing.
Through the use of these filters, the dynamic range of the TWT was
increased from 35 dB to approximately 50 dB. This range is sufficient for use
in this project.
16
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10/23/81. 6:15 PM
REF 10.0 dBir: RtfEN 20 dB
13 dB/
POS PK
V******.
JTflRT 2.00 GHz
RES SN 3 NHz
VBM 3 MHz
HKR 4.052 GHz
8.40 cBm
l.o
STOP 8.00 GHz
SWP 158 *sac
Figure 10.
Filtering characteristics of HP8432A bandpass filter.
17
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10/23/81. 6:42 PM
REF 10.0 dBm flTTEN 20 d=
10'dBx
POS PK
r
STflRT 3.50
RES BH 3 MHz
VBN 3
—^
STOP 4.50 GHz
SHP 25.0 ms»c
Figure 11.
Filtering characteristics of the HP8432A bandpass filter in series with the
HP360D lowpass filter.
18
-------
Anechpic
Material
NARDA 643
Standard Gain
Horn
PIN
Modulator
TWT
Amplifier
Filters
Bi-Directional
Coaxial Coupler
Figure 12.
Block diagram of the system to simulate the radiation pattern of a rotating radar antenna.
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Determination of System Transfer Function
Since all of the components of the system were tested and determined to be
acceptable, the whole system was assembled including the DAC from a Varian
Data Machines computer. Figure 12 illustrates the equipment set-up of the
whole system.
The entire system was tested to insure the repeatability of the power out
of the directional coupler when a particular DC voltage is applied to the bias
of the PIN. A BASIC program was written for the Varian computer to control
the voltage from the OAC. The program allows the operator to input a
particular value of voltage to be supplied from the DAC to the bias of the
PIN. For each voltage supplied to the bias, the corresponding power out of
the directional coupler was recorded. These data of DC voltage versus power
were fit to a third degree polynomial by a curve fitting program on the
HP9845B computer. This polynomial is the function necessary for a main
computer controlling program which will automate the DC voltage supplied to
the bias of the PIN modulator. These data are tabulated in Table 3 and the
resulting curve is shown in Figure 13.
20
-------
3
CT
O)
POLYNOMIflL
Power out of coupler
versug
Voltage requested
-.55--
-.525-•
X
> I t I I—h—I—I I I I I I i I—f.
01 is- •* ru
7777
iu
Ppuer (dBm)
Figure 13.
Data plot of power versus voltage.
These data were collected three separate times and were repeatable to within
=*Q.05 dB . The polynomial to fit the curve was found to be:
V * 2.14X10"6?3 + 3.67xlO~5P2 + 3.70xlO~3P - 0.63
where;
V . DC volts to the bias of the PIN modulator (volts)
P » Power out of the coupler (dBm)
Power is the independent variable so the computer operator may request the
power level he would like output from the system. "Hie computer will convert
this requested power to the appropriate value to output the DC voltage from
-------
the DAC. This voltage from the DAC will cause the system to output the
requested power.
Table 3. Power out versus voltage in.
DATA
Point #i:
Point #2 =
Point #3'
Point #4--
Point *?M
Point #6s
Point #7:
Point #8 =
Point #9:
Point #10:
Point tli:
Point #12 =
Point #13:
Point #14:
Point #15=
Point #16 =
Point #17 =
Point #i8:
Point #19 =
Point #20:
Point #21=
Point *22<
Point #23=
Point #24:
X=21
X=16.5S
X<=14.84
X=13.02
X=i2.0S
X=8 . 71
X=8 . 43
X=7.6
X=6,Si
X=4 , 22
X=3 , 02
X=i.8i
X=.28
X==-.96
X=-i.28
X=-2.24
X=-3,44
X=-5.97
X=-7.5i
X=-li.83
X=-14.05
X=-i6.67
X*-18.3
X=-19.6
Y—.51
Y=~.5S
Y=- . 56
Y=-.S7
Y=- . 575
Y=- , 59
Y=- . 592
Y=-.S95
Y=-.6
Y=- . 61
Y=~.6i5
Y«- . 62
Y=-.625
Y=- . 63
YB- . 632
Y=- . 635
Y=~ . 64
Y-~ . 65
Y»- . 655
Y=-.67
Y=-.68
Y=- . 69
Y— . 695
Y—.7
POLYNOHIAL HODEL: Y
Coefficients:
A ( 0 ) =- . 627382389708
AU)=3.6954i202060E-Q3
A(2)=3 , 66672228630E-05
A(3>=2. 14378444360E-06
Source Df
Regression 3
Residual 20
Total 23
Correlation Coeff Cr>*
-i )*XA
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Data Collection at McCarran Airport
In order to simulate a rotating radar pattern, it is necessary to first
measure actual observed radar radiation patterns. This was done by using a
unique system developed by the Nonionizing Radiation Surveillance Branch, of
EPA. This system uses a Hewlett-Packard (HP) model 9845B computer interfaced
with a HP8566A spectrum analyzer. The software has been developed by NRSB to
measure several different types of radio signals. This system is a mobile
system which may be mounted in a Dodge Ramcharger as well as in the lab. The
radar signal was received by a TECOM parabolic dish antenna mounted on top of
the ramcharger. Data collected by the system may be saved on a floppy disk
for retrieval at a later date.
The first step in making the field measurements was to test the
measurement system and software in the laboratory. The laboratory is equipped
with an Electro/Data Inc. Model AN112F log periodic antenna mounted on the
roof of the building. This antenna is mounted horizontally and is capable of
receiving microwave signals in the frequency range 1.0 - 12.4 GHz.
It was first determined that the radar installation located at McCarran
International Airport would be a good radar to use as a model since it is
easily accessible, produces a strong signal and is typical of the type of
radar for which hazard survey measurements are commonly made.
A schematic of the measuring system used in the lab is illustrated in
Figure 14. Although the laboratory measurements were intended only as a system
check and an opportunity for the operator to become proficient in using the
system, the results were worth saving. The results of the laboratory
measurements are shown in Figures 15, 16, and 17.
23
-------
Heliax
Cable
O
r^
AKJ it*> cl Electro /Data
AN112FJ^
LTT
HP 8566 A
Spectrum
Analyzer
Uitanna
System Control
and Data
0
IEEE 488
Data Bus
HP 9845 8 Q
Computer
System
Software
HP 9885 M
Drive
Figure 14,
Radar data collected in the Lab.
Figure 15 shows the CRT display of the HP 8566A spectrum analyzer
resulting from a radar pulse width measurement. For this particular pulse
width measurement, the spectrum analyzer was set up in the frequency domain
with a frequency span of 12 MHz and the center frequency of 2.75 GHz which is
the frequency of the radar signal. The horizontal axis is frequency and the
vertical axis is power. The distance between the initial null and the
terminal null is the mainlobe width which, in this case, was found to be 3.39
MHz. The pulse width is related to the mainlobe width by the formula:
' eff = (0.5)(MLW)
where: *\~aff - P^se width (seconds)
MLW = mainlobe width (Hz)
In this case the pulse width was found to be 0.59 jisec. The pulse width
measurement is not.directly pertinent for use in this project, but this figure
demonstrates the capability of the measurement system, and it is good practice
to collect all the data one can while the measurement system is set up.
Figure 16 shows the CRT display of the HP 8566A spectrum analyzer during
an antenna rotational duty cycle measurement. For this measurement, the
spectrum analyzer is set up in the time domain, so a real time picture of the
24
-------
TEST
Operator; flNDY MONHEISER
Location* Lfll
Sweep Time - .05 *ec
Inference Level * -10
Sc*1e Dfv » 10
BM
iea kHz
<1»* Width Measurement
Center freq « 2.749? GHz
cursor on Initial null
Initial Null : 2.7481
cursor on terminal null
Terminal Null : -74.374
CH= CY>: -74.477
-50
RES BM * 188 kHz
Me«iurritieni.3
I 1—I 1
Figure 15.
Center - 2.75 GHz
1200 kHz/HIV
25
-------
TEST
Operator: flNDV MONHEISER
Location: LAB
18x21'31. H:48 flM
Sweep Tim* * € set
Reference Level « -38 dB«*
Scale Div * 5
Res IM - 3 MHz
flntenna Rotational Duty Cycle
Peaks Measured at:
Location i: 76 -36.05dBw
Radar Rotation Rate:
SeeondsxRotation: 4.73
Center freq » 2.749? GHz
Location 2: 865 -36.
R P M 12.674
M»in Beam Reference: -36,075
flmenna
cycl*:{ -20.301
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-------
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REF -30,0 dBm RTTE'i 0 d
CENTER 2.749 690
RES BW 3 HHz
VBH 3 MHZ
SPRN 0 Hz
SHP 2.00 sac
Figure 17,
Peak signal from rotating radar antenna. Measurement made in lab.
-------
radar antenna's radiation pattern can be seen. A peak signal is produced when
the rotating radar antenna is directed toward the receiving antenna. The
antenna makes a complete rotation and is again directed toward the receiving
antenna producing another peak signal. Tte time between the peak signals is
the rotation rate of the antenna. The signal in Figure 16 shows a rotation
rate of 4.73 seconds which is equivalent to 12.674 rotations per minute
(RPM). This data is not just graphical, as shown in Figure 16, but associated
with the graph is an array of 1001 values. Each value is a power level in
dBm. The points are numbered from 0 to 1010 from left to right across the CRT
display. This array is the key to repr;ducing the radiation pattern. The
Varian mini-computer will convert this arr*y to DC voltages to output from the
DAC.
Figure 17 is an expanded view of the peak signal of the rotating radar
antenna. This is also defined by 1001 pol-ts. This type of display does not
show the whole 360 degrees of the antenna's rotation, but the peak signal is
much better defined.
For actual measurements in the field, the system was mounted in a Dodge
Ramcharger which was designed by NRSB ts accommodate the measuring system.
There was one major difference in the equirment used in the field. Instead of
using the log periodic antenna (as shown i-i Figure 14), a TECOM parabolic dish
antenna was used to receive the signal frini the rotating radar antenna. The
dish antenna is capable of receiving signals of either horizontal or vertical
polarization. The mobile system is shown It Figures 18 and 19.
27
-------
Figure 18.
Outside view of mobile measurement system.
28
-------
Figure 19.
Inside view of mobile measurement system.
The system was powered by a gasoline 1800 watt portable alternator which was
removed from the vehicle and placed several feet away. The dish antenna was
mounted on a Pelco pan/tilt unit which can position the dish vertically and
horizontally. The dish antenna was directed toward the rotating radar antenna
as shown in Figure 20.
Three different locations around the airport were used as measurement
sites. All the sites provided good data, but location 2 was determined to be
the best of the three locations because of the absence of nearby fences and
buildings. The data from location 2 are shown in Figures 21, 22, and 23.
These figures show the same type of data as shown in Figures 15, 16 and 17
except an external attenuation of 20 dB was attached to the front of the HP
8655A spectrum analyzer due to the strong signal at Location 2.
29
-------
Figure 20.
Dish receiving antenna directed toward rotating radar antenna.
When the laboratory measurements were compared to the field measurements,
the lab data appears to be sufficient for use in the project should the need
arise to make additional measurements.
The data collected in the field will be used as a data array for the
controlling computer program. The data may be manipulated for several
different variations of the actual signal measured in the field.
30
-------
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04/27/82. 12:20 PH
REF 10.0 dim RTTEN 20 dB
CENTER 4.100 100 000 GHz
RES BN 3 NHz VBW 3 MHz
SPRN 0 Hz
£»P 5.08 sec
Figure 23.
Peak signal from rotating Radar Antenna. Measurement made at McCarran
Airport. Horizontal axis of receiving antenna used.
33
-------
Controlling Computer Program
As explained on page 9, the amplitude modulstfan of the signal is
accomplished by using a PIN diode attenuator or norjlator. The PIN diode
attenuator is controlled by DC voltages supplied fr^a a Digital-to-Analog-
Converter (DAC), which is part of a Varian 2=ta Machines 62Q/f-100
mini-computer. In order to simulate a rotating rr^ar antenna pattern, a
computer program was written in BASIC. This program «as entitled "DRIVER."
DRIVER uses actual radar measurement data, corn-arts it to a voltage
appropriate for the system by using the transfer function, and puts this new
adjusted data into an array. These voltages are then ;jtput from the DAC in
such a fashion as to simulate the rotating radar antenna signal strength
variation. Since radar antennas have various rots.--,3nal rates, DRIVER is
capable of outputting the set of data over various i-^e periods. DRIVER is
capable of outputting 1000 data elements in less than :ne second. The output
time is entered by the operator and DRIVER outDJts the set of data
continuously until it is manually stopped. This allays the signal pattern to
be transmitted over and over in order to simulate 2 continuously rotating
radar antenna. A listing of DRIVER is shown on page fi2 sf the appendix.
34
-------
Data Transfer Between Systems
As described on page 23, measurements from a rotering radar antenna
located at McCarran Airport were made using a measurement ystem consisting of
a HP 9845B computer and a HP 8566A spectrum analyzer. Tie data from these
measurements were stored on floppy disk and a magnetic tap* cartridge. These
data may be retrieved from the floppy disk or cartridge ~n the lab. These
data on received power levels of the rotating radar aitenna signal are
represented in an array of 1001 elements. This array ii the set of data
necessary for the DRIVER data pool. The Varian mini-compute*, however, is not
capable of reading the data from the HP floppy disk or carridge. The Varian
has floppy disk drives, a high-speed paper tape reader, a rassette drive, and
a hard disk unit for mass storage input/output. The Tappy disk format,
however, is not the same for the HP and Varian computers.
After considering several alternatives, it was decitad that the data
transfer could best be accomplished by using paper tape since a Facit 4070
paper tape punch was available. The Facit, however, «as not directly
compatible with the HP 9845B computer.
Pin
1
2
3
4
5
m
Signal
Chi
Cfi2
Ch3
CM
ChS
Chfi
Pin
14
IS
16
17
18
10
Signal
_
_
_
—
c«-»
1
8
9
10
11
12
13
Ch7
Ch8
Ch9
SO
PI
PR
20
21
22
23
24
25
Eir.l
TL
+ 24V
+ SV
0V
f 14 IS 14 17 IS 19 » 21 22 23 24 25 A
I OOOOOOOOOOOOX
/OOOOOOOOOOOOOl
I I 2 3 4 3 6 7 1 » K) II O 13 J
Figure 24.
Signal connector for Facit 4070 paper tape purctu
35
-------
In order to Interface the Facit paper tape punch with the HP 9845B
computer, the voltage and logic requirements were considered. Figure 24 shows
the function of each pin for the Facit interface jack.
Pins 1 through 8 are the eight data channels and pin 9 is for the feed hole
track. Pins 11 and 12 are the punch instruction (PI) and punch ready (PR)
signals. Pin 25 is ground and pins 10, 19, 20, and 21 were not used for this
interface since the error signals, tape low signal, and the stepping direction
were not considered necessary.
The Facit interfaces using positive-true logic. A high (true) signal is a
logical 1 and a low (false) signal is a logical 0. A logical 1 corresponds to
a +3.5 to +12 volt signal and a logical 0 corresponds to a -12 to +1.5 volt
signal. Figure 25 shows the signal diagram necessary for the Facit to
interface.
1*0 (fen Omcw)
t—
1
M
10 1»
"t
I
t.
Figure 25.
Signal diagram for Facit interface.
There are only two instructions necessary for the Facit, the PI and the PR
instruction. The stepping direction (SO) will always be forward and therefore
corresponds to zero volts.
36
-------
Figure 26 shows the function of each pin for the HP 98034A HP interface
bus (HP-IB) connector and Table 4 defines the abreviations used.
Table 4. HP-IB Signal Lines
DI01
*
*
ET=O8
DAV
NRFD
NDAC
IFC
ATN
SRO
REN
EOI
Data Input Output l
*
*
Data Input Output 8 !
Data Valid
Not Ready for Data
Data Not Accepted
Interface Clear
Attention
Service Request
Remote Enable
End or Identify
Figure 26,
HP-IB Cable Pinouts.
Pins 1» 2, 3, 4, 13, 14, 15, and 16 are the eight data channels. Pins 6, 7,
and 8 are the data valid (DAV), not ready for data (NRFD), and not data
accepted (NDAC) channels. Pin 24 is signal ground. The other pins were not
used in this interface.
The HP 98034A Interface Card connects the HP 9845B computer to the HP
Interface Bus (HP-IB), allowing the computer to interact with several
different instruments such as the HP 8566A spectrum analyzer, the HP 2631S
graphics printer, the HP 59313A Analog-to-Digital converter, and other such
instruments.
37
-------
The HP-IB interfaces using -egative-true logic. A high (true) signal is a
logical 0 and a low (false) siinal is a logical 1. This is the opposite of
the Facit logic. Also, for the HP-IB, a logical 1 corresponds to <0.4 volts
while a logical 0 corresponds to >2.4 volts. Figure 27 shows the signal
diagram necessary for the HP-IB to interface.
'— i r— •*
DATA - -
(TALKER)
NW=0
(LISTENED)
NDAC
(LISTENER)
(Th» curvad hnes nQc*e *m*aoclw•** oe'o'e DAV is se< «*»
Figure 27.
Signal diagram for HP-IB.
In order to make the voltag=s and the logic compatible between the HP-IB
and the Facit, a series of DC offset inverting operational amplifiers were
constructed. A block diagram of the pin-to-pin interface through the
amplifiers is shown in Figure 28.
38
-------
Ground
12
FACIT Signal Connector
fc-,-9
? ud3:24
34567
• • » • 9 •
Ch1 Ch2 CN3 Ch4 ChS
D101
D102
PR
Ch7 ChS PI PR IP
D103 D104 TD105_jblOB JD107 D108 DAV
Ground
12 3 4 13 14 15 16 6 8
24
NDAC
2}*-
NRFD
HP-IB
Figure 28.
Pin-to-pin connector of Facit to HP-IB.
Figure 28 shows ten amplifiers. Eight of these amplifiers are for the
data channels, one is for the punch instruction, and one is for the punch
ready instruction. Notice the direction of signal transfer is from the HP-IB
to the Facit through all the amplifiers except the PR reply. The nine
amplifiers are identical. Only the PR amplifier is different. Figure 29
shows a block diagram of one of the nine identical amplifier's input/output.
39
-------
FACIT
Outputs
Amp
t
(Logical 0)
OR
Inputs +3.5 Volts
P| (Logical 0}
HP-IB
FACIT
f
•
Ouuts . Volts
(Logical 1 )
I Amp
Inputs 0Y°»*L
| (Logical 1}
HP-IB
Figure 29.
Signal in versus signal out for data amplifier.
It can be seen that if a logical 1 (<0.4V) is output from the HP-IB then a
logical 1 {* 3.5 to +12V) is input to the Facit, and vice versa. Therefore,
if a bit is set from the HP-IB, it will be set for the Facit. If the
amplifiers were not present, a logical 1 from the HP-IB would be input to the
Facit as a logical 0. The amplifiers match the logic between the Facit and
the HP-IB. Figure 30 shows a schematic circuit diagram of a data channel
amplifier. These amplifiers are DC offset by +7,5 Volts.
40
-------
Figure 30.
Schematic of data rrannel amplifier. DC offset is +7.5 volts.
The PR to NDAC araplif-=r was DC offset by +3.5 volts since the signal is
from the Fadt to the -f-lB. Figure 31 shows a block diagram of this
amplifier's input/output arc Figure 32 shows a schematic circuit diagram.
41
-------
FAC1T
*
,„ lfc +6 Volts
r"P_uts (Logical 1)
Amp
OR
1
HP-IB
FACIT
I
Amp
ft, t« - Volts
Outputs (Logrca,0)
1
HP-IB
Figure 31.
Signal in versus signal out for PR to NDAC amplifier,
Ovout
Figure 32.
Schematic of PR to NDAC amplifier. DC offset is +3.5 volts.
42
-------
These amplifiers allow the HP 9845B computer to interface to the Facit
4070 paper tape punch via the HP 98034 HP-IB. It is now possible for data on
a HP floppy disk or magnetic tape cartridge to be punched out on paper tape.
The Varian mini-computer may now read in these data via its high-speed paper
tape reader.
43
-------
Procedure for Punching Data from HP 9845B
This is a step by step procedure to be used to transfer data saved on
cartridge to paper tape using the HP 9845B computer. The procedure Is as
follows:
1. Put cartridge entitled "ANDY'S PROGRAMS" in either of the two
cartridge drives on the HP 9845B.
2. Load the program "PHOTO" from the cartridge into the computer memory.
3. Run PHOTO and recall the saved data (PHOTO will guide the operator
through this process).
4. When the statement "D(*) SHOULD BE THERE!i" appears, push STOP.
5. Load the disk entitled "ANDY'S DATA" into the disk drive.
6, Type ASSIGNf 1 to "XFER.-F"
7. Type PRINT#1; D(*}
8. Load the program "PTPVl" from the cartridge.
9. Connect the paper tape punch to the HP 9845B via the interface box
(insure the interface box is plugged in).
10. Turn on the paper tape punch and make a leader on the paper tape.
11. Push RUN.
This procedure punches out the data from the specified file onto paper
tape 1n the form of a program. The program contains DATA statements. An
example of the format is shown on page Al of the appendix.
44
-------
System Set-up in Anechoic Range
The function of an anechoic range is to provide a microwave reflection
free volume for radiated microwave testing and/or measurements. Such ranges
may take the form of completely enclosed chambers such as a room with all
surfaces covered with anechoic (non-reflective) material. This practically
eliminates signal reflection off of walls, equipment, and other fixtures.
Figures 33 and 34 show a different version of an anechoic range constructed by
the Nonionizing Radiation Surveillance Branch (NRS3) of the U.S. Environmental
Protection Agency (EPA).
Figure 33.
Anechoic range panel for mounting of measurement probe.
45
-------
Figure 34.
Anechoic range panel for mounting of standard gain horn transmitting antenna.
46
-------
The anecholc range consists of two wooden sleds mounted on casters so they
may be separated by various distances by either rolling them toward or away
from each other. The material mounted on the wooden sleds is carbon loaded
foam rubber which absorbs microwave signals such as those transmitted from the
Narda 643 standard gain horn antenna shown in Figure 34. This helps insure
that the microwave measurement probe (shown in Figure 33 as a white spherical
object) does not receive reflected signals but is exposed only to the signal
radiated directly from the horn antenna. The horn antenna and the measurement
probe are oriented toward each other as shown in Figure 35.
Figure 35.
Orientation of transmitting antenna and measurement probe in anechoic range.
Note directional coupler attached to horn antenna to facilitate measurement of
forward and reflected power at the input to the horn.
The radar simulation system was set up in the anechoic range as shown in
Figure 36. This figure shows the back of the sled shown in Figure 34. Figure
36 shows all the components of the system described in Figure 12 except the
47
-------
Varlan mini-computer with its OAC is not shown although it is connected to the
system. The NARDA 3024 coupler and the NARDA 643 standard gain horn are
mounted on the other side of the wood frame. The HP8566A spectrum analyzer
(bottom right) is used to monitor the simulated radar signal while the HP3490A
multimeter (bottom left) 1s used to monitor the DC voltage applied to the bias
port of the the PIN attenuator from the DAC. A Hughes 1277H traveling wave
tube (TWT) amplifier is used to produce a radiated signal of sufficient
intensity to be readily detectable by the hazard survey probe.
Figure 36.
Radar simulation equipment set up in anechoic range,
Figure 37 shows a NAROA 8616 electromagnetic radiation monitor mounted
behind the sled shown in Figure 33. This instrument is connected to the probe
in Figure 33. A piece of PVC pipe is used as a mount for the probe. Various
other instruments to be tested or calibrated may be mounted in the same
fashion.
48
-------
t~..
Figure 37.
Test equipment mounted in anechoic range.
49
-------
The Varian Data Machines 620/f-100 mini-computer 1s shown in Figure 38.
The DAC is located in the left panel with the cable leading to 1t. This coax
cable runs across the lab to attach to the PIN attenuator located in the
anechoic range.
Figure 38.
Varian Data Machines 620/f-100 mini-computer with DAC.
50
-------
Radar Signal Simulation
The crux of this project is to simulate the signal pattern of a rotating
radar antenna. As stated earlier In this report, measurements of an actual
rotating radar antenna were made at McCarran Airport. Several different
locations around the airport were used to make measurements of the radar using
the mobile measurement system described on page 28. Page 24 described several
different measurements of the radar antenna's pulse width, rotational duty
cycle, and peak signal. This project mainly deals with that portion of the
radar's antenna radiation pattern which best describes the peak signal created
at a given observation point by the rotating radar antenna. Figure 39 shows
one such measurement. This figure shows the signal pattern of the rotating
radar antenna as displayed on the CRT of the HP 8566A spectrum analyzer.
These data were entitled WRDAR. The horizontal axis is in the time domain
while the vertical axis shows the received power level in dBm. The peak
signal is observed when the radar antenna swings toward the receiving antenna
at the observation point and then disappears as the antenna swings away.
Notice that the power level difference from the peak to the lower level
Indicated in Figure 39 is approximately 22 dB.
51
-------
83/31/82, 4:0? PM
REF 10.0 dBm RTTEN 20 dB + 20 dB EXT. RTTEN.
NRDBR
CENTER 3.749 740 080 GHz
RES BN 3 NHz VBW 3 MHz
SPflN 0 Hz
SHP 2.00 sec
Figure 39.
Peak radar measurement made at McCarran Airport,
52
-------
In order to simulate the signal pattern shown in Figure 39, the data for
WRDAR were loaded into the Varian mini-computer. As previously described, the
computer program DRIVER will manipulate these data to produce the appropriate
DC voltages from the DAC to the system. The system was set up in the anechoic
range and connected as shown in Figure 40.
Varian
Data
Machines
620/MOO
Power
Meter
Anechoic
Material
HP 8620 C
Signal
Generator
son
Termination
_5E
NARDA 643
Standard Gain
Horn
NARDA 3024
Bi-Directional
Coaxial Coupler
Figure 40.
System set-up in anechoic range.
In order to monitor the signal being transmitted from the horn antenna,
the spectrum analyzer was connected to the forward port of the bi-directional
coupler as shown in Figure 40. The computer program DRIVER was run and the
horn antenna transmitted the simulated radar signal shown in Figure 41. The
spectrum analyzer was set to the same sweep time as in Figure 39, but the
center frequency is not the same. The actual radar signal of Figure 39 was
received at 2.75 GHz and the simulated radar signal was transmitted at 4.1
J5Hz.^Notice the difference in power level from the peak to the lower level
indicated in Figure 41 is approximately 22 dB. This is the same as in Figure
39. Also the overall pattern is consistent between the two figures. This
simulated pattern is quite acceptable for use in this project and in fact is a
very precise simulation.
53
-------
04/27/82. 12:20 PM
REF 10.0 dBrn RTTEN 20 dB ^ 3i dB EXT. flTTEN.
13
POS PK
CENTER 4.100 100 000 GHz
RES BN 3 HHz VBW 3 MHz
SPRN 0 Hz
SWP 5.00 sec
Figure 41,
Simulated radar signal pattern of WRDAR shown in Figure 17.
54
-------
Time Response of the NAROA 8616 Electromagnetic Monitor
The purpose of this project is to test the time response of microwave
survey meters (such as the NARDA 8616 electromagnetic monitor} to the
time-varying signal patterns transmitted by rotating radar antennas. The
concern about the time response is due to the fact that the high frequency
probes used for the NARDA 8616 meter use thin-film thermocouples to detect the
electric field. The thermocouples generate a DC signal which is proportional
to the power dissipated in them. This process is inherently slow for
measurements of time-varying signals. This slow time response will result in
a lower power density reading of a rotating radar antenna pattern since the
thermocouples simply cannot follow the rapidly changing power level of the
signal.
In order to test the time response of the NARDA 8616 meter with the 8621
high frequency probe, it is necessary to be capable of monitoring both the
transmitted signal and the NARDA1s response simultaneously. The response of
the NARDA may be monitored via its recorder output jack. The recorder output
corresponds to a DC voltage of +3 Volts for a full-scale reading on the meter
and 0 Volts for a zero reading.
The transmitted signal is monitored by connecting the HP 8566A spectrum
analyzer (S/A) to the forward port of the coupler as shown in Figure 40.
In order to monitor the transmitted signal and the NARDA1s response
simultaneously, a computer program entitled "RESPNS" was written for the HP
9845B computer. This program interacts with the HP 59313A Analog-to-Digital
(A/D) converter and the HP 8566A S/A as shown in Figure 42. A listing of
RESPNS is shown on page A3 of the appendix.
55
-------
HP-IB HP 9845 B
\Computer
Tt
HP 59313 A
Analog to
Digital
Converter
Recorder ' "" ] ; " "
Output— ^^
^Y^ NARDA 8616
\_Ly Electromagnetic
"- • Radiation Monitor
b'-s, NARDA 8621 •' • — hv
High Frequency.^^ s^*\. ""*""**"' ^s^
N Probe (^j %}j®Eh~ •£
Standard
Gain Horn
HP-IB
i
I
HP 8566 A
Spectrum
Analyzer
j
fr
ARDA
t
Forward
^^Power Port
3024 j— «
Coaxial
Coupler
Simulation
System
Figure 42.
Simultaneous monitoring of NARDA response time and transmitted signal.
The program RESPNS controls the interaction of the S/A and the A/D. The
S/A triggers the A/0 to begin collecting data from the NARDA1s recorder output
at the same time the S/A begins a sweep in time. While the S/A is taking a
sweep the A/D is sending data to the HP 9845B, When the S/A completes a sweep
it interrupts the A/D. This procedure insures that the data collected from
the A/D corresponds to the sweep of the S/A. RESPNS then reads the data from
the S/A and graphs both the transmitted signal and the response of the NARDA
as shown in Figure 43.
The horizontal axes in Figure 43 represent the corresponding time from a
beginning of a sweep from the S/A to the end of a sweep. The vertical axes
represent power in dBm for the simulated radar signal and power density in
mW/sq. cm for the NARDA probe response. It can be seen in Figure 43 that
there is a difference in time between when the peak value of the simulated
radar signal occurs and when the peak of the NARDA response occurs. The
straight line present in the simulated radar signal is intentionally placed
there by the Van"an computer program so the beginning and end of a rotation
may be observed.
56
-------
simulated Radar Signal
Center Frequency
I
4.18175 GHz
«.
o
D.
-50.0
2.0
1.5
1.0
0.5
0.0
NflRDR Probe Response
flctual
Value is
8.7
8
ttinc
5 .eta
5.08
Figure 43.
Time response of NAROA meter to a simulated rotating radar antenna signal
pattern.
57
-------
10.0
Simulated Radar Signal
Center Frequency
W
NflRDfi Probe Response
.0
1.5
1.0
flctuil
Value is
8-3
0
time Csec)
2.58
2.58
Figure 44.
NARDA time response to simulated rotating radar antenna signal pattern,
Notice time of 2.50 seconds.
53
-------
Simulated Radar Signal
Center Frequency
I
4.18175 GHz
i
X
«*
C. -1
ii
o
a.
2.0
1.5
i.0
0.5
0.0
fictu-al
8.3
10.00
NRRBfi Probe Response
time Csec)
10.80
Figure 45.
NARDA time response to simulated ratating radar antenna signal pattern.
Notice time of 10.0 seconds.
-------
Also notice in Figure 43 that the actual peak value is 8.7 mW/sq cm. This
is the reading that the Narda should display. The Narda only displays,
however, a peak value of approximately 1.4 mW/sq era.
Figure 43 corresponds to an antenna rotation rate of 5 seconds per
rotation. Figure ^Ilihows the response of the Narda probe when the simulated
rotation rate is increased to 2.50 seconds per rotation. As predicted, since
the Narda has less time to respond to the peak signal, it reads an even lower
value. It shoulld read 8.3 mW/sq cm. Figure 45 shows the response of the
Narda when the simulated rotation rate is decreased to 10 seconds per
rotation. The Narda has an increase amount of time to respond to the
simulated rotation, and thus displays a higher value. Notice, however, that
the peak signal is still approximately only 3 mW/sq on instead of 8.3 mW/sq cm.
60
-------
Summary
The purpose of this project was to develop a system to measure the
response time of microwave survey Instruments to rotating radar antenna
patterns.
The main crux of the project was to develop the system to simulate and
transmit a rotating radar antenna signal pattern.
The system was successfully developed to simulate the radar antenna
pattern at McCarran Airport. This is not the limit of the system, however,
since any set of data may be used by the controlling computer program, DRIVER.
This system has the capability to vary the rotational rate of the pattern
by simply inputting the desired rotational rate into the computer when
prompted to do so by the program.
This system does not transmit a pulsed signal as an actual radar signal
does, but it is not necessary to do so for testing of the NARDA probe. This
system does have the capability, however, to transmit a pulsed signal by
applying a pulse train to the external AM jack of the HP8620C sweep
oscillator. This could be useful for other applications of this system.
The response of the instrument under test (such as the NARDA 8616
Electromagnetic Radiation Monitor) may be recorded and evaluated through the
use of the HP 9845B computer. The results may be graphed and analyzed all by
the automation of the program RESPNS.
-------
List of Abbreviations Used
DAC Digital-to-Analog Converter
dB decibel
dBm decibel with respect to one milliwatt
DC direct current
EPA Environmental Protection Agency
EXT. AM External amplitude modulation
GHz gigahertz
HP Hewlett-Packard
NRSB Nonionizing Radiation Surveillance Branch
PIN Positive-Intrinsic-Negative
SWR standing wave ratio
TWT traveling wave tube
62
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References
1. Facit Company, "Facit 4070 Tape Punch Technical Description," ATVIDA8ERG,
Sweden.
2. Hewlett-Packard Company, "98034A HP-IB Interface Installation and Service
Manual," 1976.
3, Narda Microwave Corporation, "Operation and Maintenance Manual for Model
8603/8601/8602 Broadband Isotropic Radiation Monitor,"
63
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Appendix I
Example of Paper Tape Program Format
Al
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188 WITfl -38, -37. 3- -37* -37. 3* -3?. i* -38. 8* -48. 4* <-41.f* -43. If -42. t
If t DATA -42. 0* -41* -39. 3* -38. 8* -37. 4* -36. ** -3*. 1* -36. |, -3*. 4
188 MTU -36. 4, -37, -37. 8* -39. 2* -41,, 1* -43. 3* -43. 4, -46. 9 * -47. |
lit DATA -47. 2. -46. 7, -47. 2< -46. 6* -48, 3* -43, 7, -44. 7* -42. 4* -41. •
128 DATA -41. 8* -48. 4, -39. 4, -3f * -39. 3, -38. 8* -38. 9* -39. 4* -48. 2
138 DATA -48. 2- -41* -41. 6* -42. 3- -43. 3* -43. 4* -44. 1* -43,, 1* -43. 9
f 48 DATA -43. 9* -43* -44. 3* -43* -46* -46. 2* -48. 3* -38. 3* -33* -33* -33.1
138 DATA -33. 1* -33. 3* -33. 7* -32. 8* -31. 9* -38. 2* -48. 9* -46. 9* -46. 3
968 DATA -46. 3* -44. 8* -43. 2* -42. 7* -48. 3* -39. 3* -37. 9* -36. 8* -36. 2
178 DATA -36. 2, -33. 9* -33. 4, -33. 6* -33. 4* -33. 6* -36. 3* -36,,8* -37. 9
988 DATA -37. 9* -38. 2* -39. 7, -48* -41. «* -43. 3* -43,,2* -48* -49. 6*-49. 7
198 DATA -49. 7* -49. 7* -44. 7* -42. 9* -41. 6* -41,.8, -48. §* -39. 8, -48. 2
1888 DATA -48. 2* -41.1* -41.1, -43. 2* -43. 9, -49, -32. 3* -53* -31. 5* -31. t
1818 Ml* -31.1* -31. 9* -32. 3* -32. 8* -33. 3* -58. 2* -48. 2* -43* -43,,9
1828 DATA -43. 9* -44.1* -43. 8* -43. 2* -43. 8* -43.1* -44. 3* -43. 7. -43
1838 DATA -43, -42. 2* -42, -42. 2* -42. 3, -41. 8* -42. i,.-42, -41. 6, »48. 9
1848 DATA -48. 9* -48. 9* -41. 3* -41.4, -48. 8, -48. 8* -48. 7, -41. f , -43.1
1838 DATA -43.1, -44. 8, -46. 8, -47.1, -47. 3, -44. 3, -44.1* -43. 7, -42."8
1868 DAT* -42. 8* -42. 3, -41. 7* -41. 9* -48. 9* -41.1* -41. 3* -43. 4, -43
1878 DATA -43, -44. 8, -44. 7, -43. 2, -44. 2* -43. 8, -41. 8. -41. -4J, 4, -48.4
1888 DATA -48. 4, -39. ?, -41.1* -42. 7* -43. 8* -49, -43. 9, -44, -44. 3, -38. 9
1898 DATA -38. 9* -39, -38. 2, -38. 7, -39. 8, -41. 2, -48. ** -43. 4* -42. *
1188 ORTII -42. C* -4Z 7« -41. 8* -48. 3* -39. 6, -38, -37. 2, -37. 4* -37* -18
1118 DBTH -38, -39. 2, -48. 4, -42. 4, -49. 4, -46. 9* -47. 6* -44. 1, -43.1
1128 D*T* -43.1, -41. 3* -41. 2* -42. 3, -42. 6, -43. 2, -43. 8, -44, -42. |
1138 D«T« -42.1* -42. 9* -41. 7* -41. 3, -39. 9* -38. 7, -38. 2, -37. f, -37. 4
1148 D*TH -37. 4, -37* -38. 2, -37. 3, -3f. 2* -39. 3* -42.1* -44. 3, -47. 9
1138 DftTfl -47. 9* -49. 8* -49. 6* -47. 2* -46. 8. -44. 2, -42. 6, -41,7, -43.1
1168 DftTH -43.1, -43* -43.1* -42. 6* -42* -48.1* -37. 6* -36. 3* -36. 3* -3|. 8
1178 MTU -33. 8, -33. 3* -34. 7* -34. 2* -33. 4, -32. 9, -32. 4, -32. 2, -31. 7
1188 DftTfl -31. 7, -32. 1,-32. 3, -33,-33. 9*-33. 3,-36*-36. 3* -36. 4*-36. •
1198 OflTfl -36. 8* -36. 7, -36. 6* -37. 6, -38.1* -38. 9* -39. 4, -39. 7, -48. 4
1288 DATA -48. 4* -39. 7* -39. 6* -39. 2, -39. 7* -39. 4, -48. 8, -48. 4* -41. €
1218 DATA -4i: SI -39, -36. 6* -33. 6* -34. 7, -34, -32. 8*-32* -32* -31. 9
1228 DATA -31. 9* -32. 2* -33. 4* -34. 8* -36. 3, -39. 2* -43. 4* -47, -48. 4
1238 DATA -48. 4* -37. 4, -36.1* -33. 3* -33. 3* -36. 6* -37. 5* -48. 7* -44. 7
1248 DATA -44. 7* -33. 1* -43. 8* -43. 3* -45* -42. 6* -48. 8* -38. 6* -37* -34.1
1238 DATA -34. 3* -31. 8* -38. 8* -38. 3* -38. 7* -31. 6* -32. 8* -33* -38. 8
1268 DATA -38. 3* -38. 4* -38. 2* -33. 8* -33* -32. 4* -32* -38. 9* -31. 2* -31. 3
1278 DATA -38. 3* -38.1* -38. 2* -38. 2* -38. 3* -31. 7* -32. 3* -34. 7* -33. 2
•} * ft
u!
Hi:
.:• V
f.
VT
*i'-
i ? '4 1?
-
4|. ( «.
"T, tt
-------
Appendix I!
Listing of Program "DRIVER"
A2
-------
-
10 R«N THIS PROQRAN READS POUEH LEVELS IN DBN FROM DATA STATEMENTS ''
20 REN WHICH ARE TO BE ATTACHED TO THIS PROGRAN USING A LOAD COMMAND.
30 REN THE DATA IS READ INTO AN ARRAV. THE PROGRAM THEN .
40 REN CONVERTS THE POMER LEVEL TO THE CORROiPOMDINQ VOLTAGE TO -
90 REN BE OUTPUT FROM THE DAC •:
£0 DIN P<20'30> •••> \
70 DIN AC20*30> l. il
80 REN ****•**•****»*********•*•***»•***»•**•***•***•*****•••*##***>*••• ',;.
90 REN ************»***»***»**»*****»»**»*»**#**»***»*****»»»***»••***** , ,: |r
100 REN THIS SECTION OUTPUTS A CALIBRATION VOLTAGE FROM DAC
110 LET V»-. 31
120 LET NC 1>«NC 2>» 1 -"I
130 LET AC 1>«INT< 827. 4*V> r i
140 CALL DATAO« NC !>• AC 1>* 1. 30
190 PRINT "DAC IS NOW OUTPUTTING A CALIBRATION VOLTAGE. • M •-
168 PRINT "THE VOLTMETER SHOULD NOU READ 8PROX. -0. 90370 VOLTS"
178 PRINT "SET UP THE THT TO OUTPUT A POMER LESS THAN ITS SATURATION"! '
1.80 PRINT « LEVEL* ••"*;
190 REN eft************************************************************** - fi:
210 REN THIS SECTION READS FRON THE DATA POOL AND :;
220 REN OUTPUTS THE APPROPRIATE VOLTAGE FRON THE DAC
230 PRINT r lr
240 PRINT Ul
230 GOTO BM
260 PRINT
270 READ D '"-^ "
260 PRINT 'NflX LEVEL OFFSET IS "| D
290 PRINT
300 PRINT "CONFUTING11
310 FOR a* 1 TO 30
320 FOR !« 1 TO 20
330 READ P
349 REN INCREASE P(I.J) TO A MAX OPERATING LEVEL
330 LET PU*
360 NEXT I
370 NEKT «l /
3G0 PRINT "CONFUTING" /
390 FOR J« 1 TO 30
:'' i; ?l
-------
100 POR I» 1 TO 20
110 LET V- 2. 14379E-B6*Pt 3* 3. €€€70E-00*Pt 2
420 LET V*V+ 3. 69340E-03*PCI* J>- .€274
430 LET AU,J>-INT< 027. 4*V)
440 NEXT I
490 NEXT J
460 PRINT -INPUT THE ROTATIONAL RATE DESIRED CHILLISECONDS>*J
470 INPUT S
400 PRINT
490 PRINT
500 PRINT "TO STOP THE PROGRAM HIT ESC'
510 CALL TTV
120 PRINT "HERE GOES"
530 CALL CRT
540 CALL DATAO*MC I)/AC 1« i>« 999,5
590 REM CONTINUOUS LOOP MUST MANUALLY STOP PROGRAM
5€0 NAIT 1000
570 GOTO 940
500 REN
590 REN
100 REN THIS SECTION ALLOWS THE DAC TO Off ZfROED
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Appendix III
Listing of Program "RESPNS"
A3
-------
10 COM INTEGER AdOOO)
20 SHORT yoltstCn_Max,Cony,C<1000),B
100 INPUT "Input NARDA's actual peak value before rotation
110 DISP "Press CONTinue when ready to read data froM A/D"
120 PAUSE
130 DISP "Reading A/D"
140 OUTPUT 718>"R2"
ISO OUTPUT 718)"32"
160 IF NOT FRACTCI/S) THEN STATUS 718>L
170 IF L=68 THEN Talk
ISO OUTPUT 706>"H4AJ"
190 ENTER 706 BFHS 2 NQFQRMATjACI)
200 I=I+i
210 GOTO 160
220 Talk: !
230 BEEP
240 DISP "Preparing Graphics"
250 OUTPUT 718j"Ri"
260 IF AU>=9999 THEN 1=1-1
270 FOR J=0 TO I
280 C(J)=Conw*A
370 MAT SEARCH B(*>
380 MAT SEARCH B<*>,MAXj
390 IF FRACT(YMax/10) THEN Y«ax=PROUNI>(YMax/iO-»-. 5,0>*iO
400 IF FRACTCY«in/iO) THEN YMin=PROUND(YMin/iO-.5,0)*10
410 PLOTTER IS "GRAPHICS"
420 GRAPHICS
430 CALL Lgrid
440 R=St/I
450 FOR J=0 TO I
460 PLOT R*J,C(J>
470 NEXT J
480 CALL
490 J=0
SOO FOR 1=0 TO St STEP St/1000
510 PLOT I,B(J)
520 J=J+i
530 NEXT I
540 SETGU
550 LORG 5
560 LDIR 90
570 MOVE 2.1,24.8
-------
580 LABEL USING "*,K"j "Power Density"
590 MOVE 5.8,24.8
600 LABEL USING «t,KH>"<«y/sq CM)"
610 HOVE 2.1,75.2
620 LABEL USING "t,K"i"Output Power"
630 MOVE 5.8,75.2
640 LABEL USING "*,K"j "tdBM)"
650 LDIR 0
660 MOVE 70,1.7
670 LABEL USING "f,K"j"ti«e (sec)"
680 CSIZE 3.3
690 MOVE 70,98
700 LABEL USING "t,K"j"Sinulated Radar Signal"
710 MOVE 70,48.6
720 LABEL USING "t,K">"NARDA Probe Response"
730 GPRINT 115,140,"Actual Peak Value is"
740 GPRINT 15Q,i20,VAL$«," wW/CM*2"
750 GPRINT 115,400,"Center Frequency" "
760 GPRINT 150,38Q,VAL*(Cf>&" GHz"
770 END
780 SUB Lgrid(X«in,Xrtax,Xdiv,YMin,YMax,Ydiv,Type,Xt>
790 DEC
800 DIM Xft801,Tft803,Y*taQ3
810 LORG 2
820 IF Xt=i THEN LOCATE 20,120,5,45
830 IF Xt=2 THEN LOCATE 20,128,55,95
840 SCALE XMin,X«ax,YMin,YMax
850 CSIZE 3
860 Y_corr = *.04
870 Grid_x=/Xdiv-i£-10
880 IF Xt=l THEN Grid y=(Y«ax-Y«in>/Ydiv-lE-10
890 IF Xt=2 THEN Grid_y=Ydiv
900 IF Type=l THEN 930
910 GRID Grid_x,Grid_y,XMin,YMin
920 GOTO 940
930 AXES Grid_x,Grid y,XMin,YMin
940 MOVE Xrtin,Yrtin~Ylcorr
950 LABEL USING **,D"iXMin
960 MOVE Xmax,YMirt-Y_corr
970 LORG 8
980 LABEL USING "*,4D.DD">Xwax
990 CSIZE 3,1,9/15
1000 FOR Y_label=Y«in TO Ynax+iE-6 STEP Grid y*C3~Xt>
1010 MOVE XMin,Y label
1020 LABEL USING*""*,MDDZ.D,A"|Y_label, " «
1030 NEXT Y_label
1040 SUBEXIT
1050 SUBEND
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50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
E_PA 520/6-85-019
3. Recipient's Accession No.
4. Title and Subtitle Development of a System to Measure the Response
Time of Microwave Survey Instruments to Rotating Radar Antenna
Patterns
5. Report Data
June 1985
7, AuthartsJ
Paul A. Monheiser
8. Perforrning Organization Rapt, Hoi
9. Performing Organization Name and Address
U.S. Environmental Protection Agency
Office of Radiation Programs
P.O. Box 18416
Las ¥egas, NV 89114-8416
10, Projecl/Task/Work Unit No.
11. ContraeMC) or Grarrt
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