A Hewlett Packard 8410 Network Analyzer was modified to be used as an automated far-field antenna range receiver. By using external mixers, analog to digital signal conversion, and an external computer/controller, the HP8410 is capable of measuring signals as low as -110 dBm. The modified receiver is an integral part of an automated far-field range which features computer controlled test antenna positioning, system measurement parameters, and data acquisition, as well as customized measurement file management. The system described was assembled and made operational, taking advantage of off-the-shelf hardware available at minimal cost

Kunath, Richard R.

Terry, John D.

English

NASA Technical Reports Server

NASA Technical Memorandum ]03700 ._ .
/h' -3...3
Using a Modified Hewlett Packard 8410
Network Analyzer as an Automated
Far-Field Antenna Range Receiver
(NASA-TM-I03700) USING A MOUIFIED HEWLETT
PACKARD 8410 NETWORK ANALYZFR AS AN
AUTOMATED FAEFIELD ANTENNA EANGE RECEIVER
(NASA) 10 p CSCL 09C
63133
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John D. Terry and Richard R. Kunath
Lewis Research Center
Cleveland, Ohio
Prepared for the
Antenna Measurement Techniques Association Meeting
PhiI_i-delphia, Pennsylvania, October 8"II, 1990
https://ntrs.nasa.gov/search.jsp?R=19910010036 2020-03-19T18:44:11+00:00Z
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USING A MODIFIED HEWLETT PACKARD 8410 NETWORK ANALYZER
AS AN AUTOMATED FAR-FIELD ANTENNA RANGE RECEIVER
John D. Terry and Richard R. Kunath
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135
SbFvLMARY
A Hewlett Packard 8410 Network Analyzer was modified to be used as an
automated far-field antenna range receiver. By using external mixers, analog
to digital signal conversion, and an external computer/controller, the HP8410
is capable of measuring signals as low as -110 dBm. The modified receiver is
an integral part of an automated far-field range which features computer con-
trolled test antenna positioning, system measurement parameters, and data
acquisition, as well as customized measurement file management. The system
described was assembled and made operational taking advantage of off-the-shelf
hardware available at minimal cost.
INTRODUCTION
As part of its mission to develop and evaluate advanced antenna feed
designs, the RF and Antenna Technology Branch of NASA Lewis Research Center's
Space Electronics Division required an automated far-field antenna test range.
The principle piece of instrumentation in any microwave measurement system is
the microwave receiver, For antenna measurements, the receiver must have the
capability to measure both the relative (and sometimes absolute) phase and
amplitude between a reference and test signal.
Microwave receivers having these capabilities have been developed for the
measurement of microwave device and circuit characterization. These receivers
are the main component in microwave network analyzers. The Hewlett Packard
8410 Network Analyzer is implemented using such a receiver. When configured
for S-parameter measurements of microwave devices and circuits, the system can-
not readily be used as an antenna measurement receiver. However, by reconfi-
guring the receiver, the HP8410 can be converted into a sensitive antenna
measurement receiver at minimal cost.
THE HP8410 NETWORK ANALYZER SYSTEM
Shown in figure 1 is the original configuration of the HP8410 microwave
receiver as a network analyzer. The key components of the system are an RF
source, a low frequency synthesizer, a harmonic generator, and the receiver
(ref. 1). The system is phaselocked by using a highly stable LO (local oscil-
lator) signal and a phase comparator to generate an error signal which is used
to FM modulate the RF source for a constant intermediate frequency (IF) signal
into the receiver. The RF signal is split to provide a reference signal to the
receiver and a test signal to stimulate the device under test (DUT). Both RF
signals are applied to a harmonic generator which serves two functions; together
with the synthesizer, the harmonic generator is used to generate the stable LO
source, and it also contains mixers to downconvert the reference and test chan-
nel signals to the IF frequency (20.278 MHz). The IF signals entering the re-
ceiver are downconverted a second time to 278.78 kHz and then compared to
determine the phase and amplitude difference between them.
MODIFIED HP8410 MICROWAVE RECEIVER SYSTEM
The modified HP8410 microwave receiver system is shown in figure 2. In
order to function properly, the receiver must receive both a reference and a
test IF signal at 20.278 MHz. The modified system develops these signals
directly using external mixers and an independent LO source, rather than the
harmonic generator and a multiplied, low frequency synthesizer. The external
mixers used have considerably less conversion loss as compared to the mixers
in the harmonic generator. Two sets of mixers are used to provide frequency
.neasurement capability up to 40 GHz. One set of mixers enables fundamental
mixing up to 18 GHz, and a second set of mixers enable even harmonic mixing up
to 40 GHz. Above 26.5 GHz, a frequency doubter/amplifier is used to generate
the required RF signal.
MODIFIED HP8410 MICROWAVERECEIVER CHARACTERISTICS
The system described above exhibits remarkable sensitivity. The manufac-
turer specifies the dynamic range at approximately 65 dB. However, this is
only the dynamic range of the receiver's display module. By adjusting the ref-
erence level input, it is possible to measure test channel signals as low as
-110 dBm. These results were measured by correlating the signal displayed on
the HP8410 with a signal displayed on a spectrum analyzer whose resolution
bandwidth was set to mimic that of the HP8410 receiver. According to the manu-
facturer, the maximum iF signal level that can be applied is nominally 0 dBm,
which puts the dynamic range at 110 dB. The increased performance is largely
due to two factors, the relative adjustment of the reference signal just dis-
cussed, and the lower conversion loss achievable with external mixers. If
even higher quality measurements are required, the phase comparator can be
eliminated and a second microwave synthesizer used for the RF source. In this
configuration, the modified HP8410 system imitates that of an HP8510 system.
The modified HP8410 receiver is also easily interfaced with an external
computer/controller. The HP8410 provides analog outputs of the signals dis-
played on its CRT. These phase and amplitude signals can be converted to
digital signals by using either analog to digital converters, or by using a
digital voltmeter of the appropriate range. The phaselock status of the sys-
tem can be monitored in a similar fashion. By monitoring these signals, this
measurement system is capable of rendering fixed frequency amplitude and phase
measurements, as well as stepped frequency scan measurements.
SYSTEM AUTOMATION
This section describes both the hardware and software integration, and
automation of the modified HP8410 receiver with the antenna positioning and
data acquisition subsystems. The key elements of the system automation are the
system controller and the positioning hardware. The system controller controls
the overall operation of a test run, as well as the processing of the measured
data. The positioning hardware, on the other hand, mainly controls the motion
of the antenna under test and displays data during a test run.
System Controller
The heart of the system controller is an HP308 personal computer. This PC
comes equipped with two processors and several [/0 interfaces. One processor
operates in the DOS 3.3 environment, the other, in the Hewlett Packard (HP)
BASIC 5.0 environment. The two processors communicate through a port connect-
ing them. The versatility of this machine has been fully exploited in the sys-
tem controlling. Test parameters are specified in the DOS under the control of
a software program, and data is taken while in the HP B_SIC environment under
the control of another software program.
SYSTEM SOFTWARE CHARACTERISTICS AND MANLCE_N_
DOS Environment
The first program discussed is the far-field antenna measurement program
(FA_). The program operates in the DOS environment and is menu driven. This
program has four menu options: create control file, edit control file, view
data, and run test.
Create Control File
The first option is used to create control files for swept frequency and
pattern measurements. The control files are used to specify test conditions
during a run. For the swept frequency measurement, the radiated power level
and the frequency scan are given. For a pattern measurement, the radiated
power level and angular scan are given. For either test, the parameters are
saved in files to be edited or executed at a later time.
Edit Control File
The second option is used to modify the control files created in option
one. The control files can be renamed, deleted, or printed from within this
option. Also, the contents of the file can be edited and saved under the same
filename or a different filename. This facilitates changing test conditions
when multiple tests are made.
View Data
The third option is used to view data stored in files from previously
executed tests. A variety of display options is available. Some examples are:
amplitude versus scan angle, phase versus scan angle, amplitude versus scan
frequency, and phase versus scan frequency. Each of these displays can be
plotted to an HP7475A pen plotter in this option. Examples of these plots are
shown in figures 3 to 6 respectively.
Run Test
The last option is used to run a test. This option stores a specified
filename in a buffer to be read by the second software program. In this option
control transfers from DOS to the HP BASIC operating system.
HP BASIC Environment
The second program, called Analyzer, operates in the HP BASIC environment.
It executes all the parameters in the file specified in the buffer. The Ana-
lyzer program reads the content of the control file via the communications
port. It then uses this information to program both microwave hardware and
electronic hardware used in the system.
SYSTEM HARDWARECHARACTERISTICS
Microwave Hardware
The microwave hardware is programmed through the IEEE-488 interface of the
computer. The microwave hardware consists of an HP8350A sweep oscillator/
signal generator and an HP8672A synthesizer configured as the LO. The signal
generator is programmed for either stepped continuous wave or continuous wave
operations depending on whether a swept frequency or a pattern measurement has
been specified. The signal generator is also programmed to the power level
specified in the control file. The LO is programmed to the calculated fre-
quency which maintains phaselock with the signal generator.
Automation Hardware
The automation hardware consists of the positioning hardware and the
HP59313A analog-to-digital (a/d) converter. The positioning hardware is pro-
grammed through the general purpose input/output (gpio) interface of the com-
puter. The test antenna is positioned to boresight during a swept frequency
measurement and swept over an angular scan during pattern measurement. The a/d
converter is programmed through the IEEE-488 interface. The analog outputs for
the relative amplitude and phase of the ITP8410 receiver are connected to the
inputs of two channels of the a/d converter. The a/d converter is programmed
to read both channels at each frequency step, and angular position for swept
frequency and pattern measurements, respectively. The PC stores the data in
files and displays the data on the screen. In addition, the data is also plot-
ted to an HP7475A pen plotter.
4
Positioning Hardware
The other key element of the automation process is the positioning hard-
ware. The positioning hardware is used to move the test antenna to any speci-
fied position or positions. The positioning hardware includes a three axes
motor driver unit, a Scientific Atlanta (SA) 5300 Series pedestal, a SA 1800
Series dual synchro display, and a synchro display select unit.
The motion of the test antenna is controlled by the pedestal and three
axes motor driver. The test antenna is mounted to the SA pedestal. The three
axes motor driver unit controls the azimuth and elevation motors of the pedes-
tal. This unit was designed and fabricated in-house. The unit can control
both DC servo and stepper motors. The axes are selecte_ electronically by the
PC. In addition to controlling the motors of the pedestal, this unit also has
front panel displays of the amplitude and phase measured by the HP8410 during a
test.
The position of the test antenna is read by the PC through the SA digital
synch_'o display and the synchro select unit. The digital synchro display
simul'aneously monitors the azimuth and elevation synchro of the pedestal. The
synchro select unit electronically selects the display corresponding to the
axis being controlled by the PC. This unit was also designed and fabricated
in-house.
CONCLUSIONS
The development of an automated far-field antenna range measurement system
featuring a modified HP8410 microwave receiver has been presented. With the
addition of a few external components, the HP8410 network analyzer has been
modified to function as a highly sensitive, general purpose microwave receiver,
suitable for pattern and frequency swept antenna measurements. The system
automation described in this paper combines techniques demonstrated in other
automated systems (refs. 2 and 3) and techniques unique to this system. Menu
driven software programs have been used in other automated systems and data
processing in the HP BASIC environment has also been used. However, incorpo-
rating both techniques in one system and using control files to coordinate the
operation of both techniques has not been demonstrated previously. Also, each
of the two units of the positioning hardware has been fabricated and assembled
in-house at minimal cost. A similar cost savings has been realized by the
in-house development of the automation software.
REFERENCES
1. Beauchamp, B.: A Low Cost, Unified Approach to Antenna Data Processing.
AMTA Proceedings, Antenna Measurement Techniques Association, Atlanta, GA,
Sept. 1988.
2. Shively, D.G.; and Stutzman, W.L.: A Low Cost, PC Based Far-Field Antenna
Range. AMTA Proceedings, Antenna Measurement Techniques Association,
Atlanta, GA, Sept. 1988.
3. Operating and Service Manual for the HP8410B Network Analyzer, Hewlett
Packard Company, June 1979.
H P8709A
SYNCHRONIZER
_IUNING
20.278MHz HP84t2 MAGNITUDE/
I PHASE DtSPLAY
RECEIVER
HP8350 SWEEP
GENERATOR
---'_ HP8411 HARMONIC
CONVERTER
( 0.11-I8 GHz }
:TEST
HP3335A
SYNTHESIZEE
Figure1.--Unmodified HP8410 configuration.
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SYNCHRO SELEC T(]R I
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Figure 2.--Automated far field antenna measurement system using modified H P8410.
ORIGINAL PAGE iS
OF POOR QUALITY
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ORIGINAL
OF POOR
National Aeronaulics and
Space Administralion
1. Report No.
NASA TM-103700
4. Title and Subtitle
Using a Modified Hewlett Packard 8410 Network Analyzer as an Automated
Report Documentation Page
2. Government Accession No. 3. Recipient's Catalog No.
5. Report Date
Far-Field Antenna Range Receiver
7. Author(s)
John D. Terry and Richard R. Kunath
9. Performing Organization Name and Address
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135-3191
12. Sponsoring Agency Name and Address
National Aeronautics and Space Administration
Washington, D.C. 20546-0001
6. Performing Organization Code
8. Performing Organization Report No.
E-5922
10. Work Unit No.
650-60-20
11. Contract or Grant No.
13. Type of Report and Period Covered
Technical Memorandum
14, Sponsoring Agency Code
15. Supplementary Notes
Prepared for the Antenna Measurement Techniques Association Meeting, Philadelphia, Pennsylvania, October
8-11, 1990.
16, Abstract
A Hewlett Packard 8410 Network Analyzer was modified to be used as an automated far-field antenna range
receiver. By using external mixers, analog to digital signal conversion, and an external computer/controller, the
HP8410 is capable of measuring signals as low as - 110 dBm. The modified rcceiver is an integral part of an
automated far-field range which features computer controlled test antenna positioning, system measurement
parameters, and data acquisition, as well as customized measurement file management. The system described was
assembled and made operational taking advantage of off-the-shelf hardware available at minimal cost.
17. Key Words (Suggested by Author(s))
Microwave instrumentation
Antenna measurements
Far-field
18, Distribution Statement
Unclassified - Unlimited
Subject Category 33
19. Security Classif. (of this report) 120. Security Classif. (of this page) 121. No. of pages
Unclassified [ Unclassified I 10
NASAFORM1626OCT86 *For sale by the National Technical Information Service, Springfield, Virginia 22161
22. Price*
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