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Variance and spectra of angle-of-arrival and Doppler fluctuations caused by ionospheric scintillation

May 1, 1978
  |
Journal Article
Author:
Robert K. Crane
Published in:
J. of Geophysical Research, May 1, 1978, Vol. 83, No. A5, pp. 2091-2102.
Topic:
radar
R&D area:
R&D group:

Summary

The variance and spectra of angle-of-arrival and Doppler fluctuations were estimated by using 150- and 400-MHz transmissions from the low-orbiting U.S. Navy navigation satellites observed at the Millstone Hill radar facility. A theoretical model for the variance and spectra was also constructed by using the Rytov approximation and a power law power spectrum model for the electron density fluctuations. The model provided a means for the estimation of both the axial ratio and the location of the lower edge of the irregularity region, using only angle-of-arrival and Doppler observations made at a single location. Good agreement was obtained between the model estimates and observations. Analysis of data from two magnetic storms revealed simultaneous occurrences of E region and F region irregularities at invariant latitudes north of 56°.
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Summary

The variance and spectra of angle-of-arrival and Doppler fluctuations were estimated by using 150- and 400-MHz transmissions from the low-orbiting U.S. Navy navigation satellites observed at the Millstone Hill radar facility. A theoretical model for the variance and spectra was also constructed by using the Rytov approximation and a power...

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Variance and spectra of angle-of-arrival and Doppler fluctuations caused by ionospheric scintillation

Automating radars for air traffic control

February 2, 1978
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Conference Paper
Author:
Charles E. Muehe
…
Published in:
Electronic Show and Convention, Electro, Boston, MA, 23-25 March 1978.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Developments in digital signal processing over the past few years have improved the detection and false alarm properties of air surveillance radars to such an extent that automatic radar tracking of all aircraft within the radar's coverage volume has become a reality. This paper derives the radar requirements to support tracking in a fully automated air traffic control system.
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Summary

Developments in digital signal processing over the past few years have improved the detection and false alarm properties of air surveillance radars to such an extent that automatic radar tracking of all aircraft within the radar's coverage volume has become a reality. This paper derives the radar requirements to support...

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Automating radars for air traffic control

Interferometer design for elevation angle estimation

August 21, 1977
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Journal Article
Author:
Robert J. McAulay
Published in:
IEEE Trans. Aerosp. Electron. Syst., Vol. AES-13, No. 5, September 1977, pp. 486-503.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Radars that are developed for the purpose of monitoring aircraft landings in the terminal air traffic control system can be designed to exploit the relatively high signal-to-noise ratio that characterizes the power budgets calculated for such a link. An interferometer using a pair of low gain antennas can be used to obtain passive coverage over a target azimuth and elevation sector. A large baseline can be used to obtain the desired elevation angle estimation accuracy. In this paper an optimal tradeoff between the width of the subarray aperture and the width of the interferometer baseline is performed that achieves a specified elevation angle estimation error while minimizing the overall height of the interferometer configuration. The algorithm searches through the class of antenna patterns that can be synthesized from so-called finite impulse response, linear phase digital filters. For the specific problem of designing an elevation sensor for monitoring landing aircraft on final approach, the elevation angle can be estimated with no more than 1-mrad rms error when the aircraft is within 60 azimuth, 2.5 to 40 elevation, using two 7-wavelength subarray antennas spaced 8 wave-lengths apart. The design of a separate sensor for resolving the interferometer ambiguities is formulated as a hypothesis testing problem and solved using statistical decision theory. A bound on the probability of an ambiguity error is derived that accounts for the effects of ground reflection multipath and receiver noise.
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Summary

Radars that are developed for the purpose of monitoring aircraft landings in the terminal air traffic control system can be designed to exploit the relatively high signal-to-noise ratio that characterizes the power budgets calculated for such a link. An interferometer using a pair of low gain antennas can be used...

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Interferometer design for elevation angle estimation

Airborne radars for surveillance and weapon delivery

July 15, 1977
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Technical Report
Author:
Charles E. Muehe
Published in:
MIT Lincoln Laboratory Report TN-1977-23
Topic:
airborne surveillance
R&D area:
R&D group:

Summary

Airborne radars such as AW ACS capable of large area surveillance of aircraft over both land and sea have become a reality in the past few years. Soon to follow are radars capable of large area surveillance of moving ground traffic. Through their ability to accurately report enemy movement and to target individual enemy ground vehicles, these radars will undoubtedly have a large impact on intelligence gathering, resource allocation, command, control and the damage assessment functions. This report describes relationships and trade-offs fundamental in the design of airborne surveillance radars in various operational roles. It describes radar capabilities which can be achieved using modern technology including array antennas, advanced waveforms and advanced signal processing techniques.
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Summary

Airborne radars such as AW ACS capable of large area surveillance of aircraft over both land and sea have become a reality in the past few years. Soon to follow are radars capable of large area surveillance of moving ground traffic. Through their ability to accurately report enemy movement and...

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Airborne radars for surveillance and weapon delivery

Coaxial magnetron spectra and instabilities

June 24, 1977
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Project Report
Author:
Melvin Labitt
Published in:
MIT Lincoln Laboratory Report ATC-74
Topic:
surveillance
R&D area:
R&D group:

Summary

Application of advanced radar clutter rejection techniques to FAA airport surveillance and enroute radars is constrained by inherent instabilities and spectral properties of the device used with the radar transmitter to generate high level RF pulse energy, and the degree to which its spectrum can be influenced by the circuit in which it operates. Coaxial magnetrons are believed to be spectrally pure, controllable and stable, and to embody other characteristics such as long life, which make them attractive replacements for the magnetrons presently employed. This report summarizes the results of extensive measurements made on a conventional S-band magnetron (presently employed in the ASR-7 radar) and a coaxial magnetron of equivalent pulse and power rating to compare their instabilities and spectral properties.
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Summary

Application of advanced radar clutter rejection techniques to FAA airport surveillance and enroute radars is constrained by inherent instabilities and spectral properties of the device used with the radar transmitter to generate high level RF pulse energy, and the degree to which its spectrum can be influenced by the circuit...

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Coaxial magnetron spectra and instabilities

Advanced signal processing for airport surveillance radars

June 11, 1977
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Conference Paper
Author:
Lincoln Cartledge
…
Published in:
IEEE Electronics and Aerospace Systems Convention, EASCON, 7-9 October 1974.
Topic:
air traffic control
R&D area:
R&D group:

Summary

The inclusion of airport surveillance radars (ASR) in an automated air traffic control system, such as the ARTS-III, has been limited by the present radar's capability to automatically reject ground clutter, weather clutter and angels while still maintaining good detectability on all aircraft within their coverage patterns. Analytical and experimental studies have been performed which indicate that new techniques can significantly enhance the automated capability of these radars. A special-purpose, hard-wired, digital signal processor has been designed, built and tested which provides near-optimum target detection over the entire ASR coverage out to 48 nmi. The processor which coherently integrates eight pulses has both a fine grained clutter map for optimal thresholding in high ground clutter environments and a mean-level thresholding scheme for filtering those Doppler cells which contain heavy precipitation. Because of the processor's ability to detect targets in a high ground clutter environment, the ASR's will be able to operate their antennas at lower elevation angles and, thus, have better coverage of low flying aircraft near the terminal. The processor is initially being tested on a highly modified, coherent S-band, FPR-18 radar. The stability of the klystron transmitter was improved so that it would not limit system performance and a new, wide dynamic range, linear receiver was provided.
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Summary

The inclusion of airport surveillance radars (ASR) in an automated air traffic control system, such as the ARTS-III, has been limited by the present radar's capability to automatically reject ground clutter, weather clutter and angels while still maintaining good detectability on all aircraft within their coverage patterns. Analytical and experimental...

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Advanced signal processing for airport surveillance radars

Comparison of the performance of the moving target detector and the radar video digitizer

April 26, 1977
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Project Report
Author:
Robert M. O'Donnell
…
Published in:
MIT Lincoln Laboratory Report ATC-70
Topic:
surveillance
R&D area:
R&D group:

Summary

Results of side by side simultaneous tests to compare the performance of the Moving Target Detector (MID) digital signal processor and that of a newly developed adaptive sliding window detector, the Radar Video Digitizer (RVD-4), are described. The MTD, used with a highly modified FPS-18, employs coherent linear doppler filtering, adaptive thresholding, and a fine grained clutter map which together reject all forms of clutter simultaneously. The RVD-4, which was used with an ASR-7, is a non-linear, non-coherent digital processor. The detection and false alarm performance of both processors in thermal noise was identical. Measured detection and sub-clutter visibility performance of the MTD on controlled aircraft flying in heavy rain, in heavy ground clutter, and at near-zero radial velocity is shown to be superior to that of the RVD-4. MID report data is also shown to be more accurate than the RVD-4 data resulting in improved ARTS-Ill tracker performance when using MID processed data.
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Summary

Results of side by side simultaneous tests to compare the performance of the Moving Target Detector (MID) digital signal processor and that of a newly developed adaptive sliding window detector, the Radar Video Digitizer (RVD-4), are described. The MTD, used with a highly modified FPS-18, employs coherent linear doppler filtering...

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Comparison of the performance of the moving target detector and the radar video digitizer

Description and performance evaluation of the moving target detector

March 8, 1977
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Project Report
Author:
Lincoln Cartledge
…
Published in:
MIT Lincoln Laboratory Report ATC-69
Topic:
surveillance
R&D area:
R&D group:

Summary

Under FAA sponsorship, MIT, Lincoln Laboratory has developed new techniques which significantly enhance automated aircraft detection in all forms of clutter. These techniques are embodied in a digital signal processor called the Moving Target Detector (MTD). This processor has been integrated into the ARTS-III system at the National Aviation Facilities Experimental Center, Atlantic City, New Jersey (NAFEC) and has undergone testing during the summer of 1975. This report contains a description of the MTD design and its evaluation tests. A detailed discussion of the significance of the results is also presented. The detection performance of the MTD was excellent in the clear, in rain and ground clutter, and false alarms were under complete control. The MTD processed range and azimuth data was very accurate, and the MTJI did not suffer from track dropouts as did the conventional MTI when the aircraft track became tangential to the radar. Performance was excellent on magnetron as well as klystron-type radars with the exception- of second-time-around clutter cancellation.
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Summary

Under FAA sponsorship, MIT, Lincoln Laboratory has developed new techniques which significantly enhance automated aircraft detection in all forms of clutter. These techniques are embodied in a digital signal processor called the Moving Target Detector (MTD). This processor has been integrated into the ARTS-III system at the National Aviation Facilities...

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Description and performance evaluation of the moving target detector

DABS monopulse summary

February 4, 1977
  |
Project Report
Author:
David Karp
…
Published in:
MIT Lincoln Laboratory Report ATC-72
Topic:
surveillance
R&D area:
R&D group:

Summary

Improved azimuthal resolution of proximate aircraft necessary to support ATC automation can be achieved by beacon surveillance systems employing monopulse angle estimation techniques described in this report. Included in the report are the results of beacon surveillance monopulse system analyses relating to off-boresight angle estimation using short (1/2 micro sec) pulses: the effects of specular and diffuse multipath signal return; the effects of overlapping ATCRBS fruit replies, and the problems of antenna pattern design. These topics have been studied in detail as part of the Lincoln Laboratory disign of the Discrete Address Beacon System (DABS). This report summarizes analytical results obtained. In general, it has been concluded that the ATC environment does not pose a serious problem to the use of the monopulse concept for beacon system direction finding and that sufficient direction finding accuracy can be obtained using a small number of narrow pulses for each scan.
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Summary

Improved azimuthal resolution of proximate aircraft necessary to support ATC automation can be achieved by beacon surveillance systems employing monopulse angle estimation techniques described in this report. Included in the report are the results of beacon surveillance monopulse system analyses relating to off-boresight angle estimation using short (1/2 micro sec)...

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DABS monopulse summary

Ionospheric scintillation

February 1, 1977
  |
Journal Article
Author:
Robert K. Crane
Published in:
Proc. of the IEEE, Vol. 65, No. 2, February 1977, pp. 180-199.
Topic:
radar
R&D area:
R&D group:

Summary

Available observations of ionospheric scintillation are analyzed to evaluate the adequacy of existing models used for the interpretation of scintillation data. The theoretical models are reviewed and the frequency and propagation geometry dependences predicted by the models are compared with the observations. The models were used to construct scintillation occurrence distribution functions which show that scintillation phenomena significantly affect the design of transionospheric radar or communication systems operating at frequencies below 1 GHz. Diversity schemes useful for mitigation of scintillation effects are considered. Mention is made of the geophysical processes thought to be responsible for scintillation.
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Summary

Available observations of ionospheric scintillation are analyzed to evaluate the adequacy of existing models used for the interpretation of scintillation data. The theoretical models are reviewed and the frequency and propagation geometry dependences predicted by the models are compared with the observations. The models were used to construct scintillation occurrence...

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Ionospheric scintillation
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