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1. AGENCY USE ONLY (Leave
blank)
2. REPORT DATE
5 August 1 998
3. REPORT TYPE miw - -
Final Report, covers 1 August 1997 - 1 August 1998
4. TITLE AND SUBTITLE
A passive radar for atmospheric remote sensing using
commercial FM broadcasts
6. AUTHOR(S)
John D. Sahr
5. FUNDING NUMBERS
AFOSR Grant
F4 9620-96-1-0138
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
[email protected]
206 543 3842
8. PERFORMING ORGANIZATION
REPORT NUMBER
Department of Electrical Engineering
University of Washington box 352500
Seattle, Washington 98195-2500
9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES)
Air Force Office of Scientific Research
1 10 Duncan Avenue, Suite B1 15
Bolling AFB, DC 20332
10. SPONSORING / MONITORING
AGENCY REPORT NUMBER
11. SUPPLEMENTARY NOTES
This is the final report for this grant
12a. DISTRIBUTION / AVAILABILITY STATEMENT
Distribution unlimited
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200 Words)
We are developing a completely passive bistatic radar using commercial FM broadcasts near
100 MHz. By correlating a clean copy of the broadcasts with the weak, delayed scatter at
a remote site, we will generate the full range-Doppler profile of ion acoustic turbulence
near the auroral electro jets. More precisely we will be calculating the cross ambiguity
function of data from two receivers separated by approximately 100 km, intending to detect
targets at slant ranges as large as 1000 km.
The AFOSR funded portion of this project is now complete. We have completed construction
of a fully functional bistatic radar, synchronized in time and frequency using Global
Positioning System (GPS) technology. We have successfully detected aircraft at ranges as
great as 240 km with 1.5 m/s velocity resolution. Detection of aircraft is an important
step in detecting auroral turbulence, which has similar scattered power and Doppler shift.
An overview of this work has been presented at two international conferences and resulted
in two refereed publications and three MS theses.
14. SUBJECT TERMS
Passive bistatic radar, ionosphere, radar signal processing
15. NUMBER OF PAGES
3
16. PRICE CODE
17. SECURITY CLASSIFICATION
OF REPORT
unclassified
18. SECURITY CLASSIFICATION
OF THIS PAGE
unclassified
19. SECURITY CLASSIFICATION
OF ABSTRACT
unclassified
20. LIMITATION OF ABSTRACT
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NSN 7540-01-280-5500
Standard Form 298 (Rev. 2-89)
Prescribed by ANSI Std. 239-1 8
298-102
1 Objectives
This research project is devoted to the development of a completely passive bistatic radar for studies of turbulence
in the lower ionosphere. In particular we propose to take advantage of commercial FM broadcasts near 100 MHz
which have high average power and excellent ambiguity function, corresponding to superb sensitivity and full Doppler
spectrum recovery with fine range resolution.
Although our effort is aimed at upper atmospheric studies, this radar system should be quite effective at detecting
meteor trails, aircraft, and possibly even satellites.
2 Status of Effort
In the last year we have completed full proof-of-concept experiments and successfully detected two classes of targets
with a completely passive system. Both aircraft and geologic features (Mt. Rainier) are regularly detected. Significant
improvements in the basic signal processing enable us to process data at approximately one percent of real time. We
can continuously record data until the recording media fill, which is approximately one hour.
As this AFOSR grant closes four graduate students are working on the project, as well as eight undergraduate
students. The students currently are working to improve the signal processing algorithms for greater efficiency and
resolution, accomodating various systematic errors in the receivers.
We maintain a World Wide Web page for recent results:
http: //res . ee.washington.edu/ spp/Projects/Manastash/ status/mrr .html
We are seeking funding from both the National Science Foundation and AFOSR to continue activity on this project.
Our total request from both agencies is $200,000 per year.
3 Accomplishments
Mr Frank Lind has successfully completed development of a working bistatic receiver pair. These receivers are synchro¬
nized using the Global Positioning System to about 100 ns sampling jitter, and about 0.001 Hz in center frequency. The
receivers have very simple direct conversion topology, and are inexpensively constructed from modern surface mount
components largely intended for cellular telephone service. Each receiver is controlled by a conventional personal com¬
puter running the linux operating system, and include multichannel synchronous analog to digital converters (12 bits,
8 channels). The entire receiver system can be duplicated for about $10,000 per receiver station.
The receivers have been in nearly continuous operation since November 1997; some power outages created problems
at the remote site which have been mitigated by the addition of uninterruptible power supplies. Currently the system
is quite robust and we are very pleased with its performance ... although we also have several enhancements in mind
for new students to develop.
Ms Dawn Gidner has built an excellent log-periodic antenna to provide useful azimuthal control of the remote site,
and we intend to increase the gain to about 20 dB in the next year.
This project has attracted considerable attention in the international geophysics community. We have been invited
to speak at the URSI General Assembly (Lille, France, 1996), and the Western Pacific meeting of the AGU (Taipei,
Taiwan, 1998) to describe this completely passive radar system.
Last summer Mr Chad Lindstrom completed his MS thesis using the radar system to detect aircraft. Mr Lindstrom
is now serving at the USAF Phillips Lab at Kirtland Air Force Base, New Mexico.
4 Personnel Supported
1. Dr John D. Sahr, PI
2. Mr FYank Lind, second year graduate student (Geophysics Department)
3. Mr Chad Lindstrom, beginning graduate student (Electrical Enginering)
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5 Technical Publications
5.1 Journal Publications
1. Sahr and Lind, “The Manastash Ridge Radar: A Passive Bistatic Radar for Upper Atmospheric Radio Science,”
Radio Science, v32, p2345-58, 1997.
2. Sahr and Lind, “Passive Radio Remote Sensing of the Atmosphere using Transmitters of Opportunity,” Radio
Science Bulletin, v284, p4-7, 1998
5.2 other
It is expected that Mr Rank Lind will complete his PhD in August 1999. His dissertation will contain substantial
documentation describing this radar. Currently we have undertaken and standard documentation methodology for our
hardware and software, and there are approximately 200 pages of such documentation that we have produced ourselves
(as opposed to having assembled from vendors, etc.). Some of this documentation may be found on the World Wide
Web:
http : //res . ee . Washington . edu/ spp / Manuals /mrr Jiwman . pdf
6 Inter act ions /Transit ions
6.1 Conference Presentations
1. Sahr, Passive Correlative Radar Methods, URSI General Assembly, Lille France, August 1996.
2. Lind and Sahr, The Manastash Ridge Radar, Western Pacific Meeting of the AGU, Taipei Taiwan, July 1998
6.2 Transitions
Dr Richard Lodwig of Lockheed Martin Federal Systems visited us last December. We investigated the possibility of
receiving support from Lockheed, which has a significant development in a related passive radar method. Unfortunately
the University and Lockheed could not resolve differences of opinion in the ownership of intellectual property, and so
that source of support did not blossom.
Mr Chad Lindstrom completed his MS thesis in July 1997, and subsequently took a position in the Air Force at
Phillips Lab, Kirtland Air Force Base. Mr Lindstrom’s thesis dealt with the engineering issues relevant to a monostatic
passive radar system, as opposed to the bistatic system which is our main focus.
7 Patent Disclosures
(none)
8 Honors
• John D. Sahr: Henry Booker Fellowship, URSI-US National Committee, presented at URSI General Assembly,
Lille, France, August 1996.
• Rank Lind: First Prize, Student Poster Contest, UW Department of Electrical Engineering, ’’Passive Bistatic
Radar for Remote Sensing of Ionospheric Turbulence,” April 1996.
• For publications and research related to this effort, John Sahr was promoted to Associate Professor in Autumn
1997.
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