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Obtaining low sidelobes using non-linear FM pulse compression

November 4, 1994
  |
Project Report
Author:
Melvin Labitt
Published in:
MIT Lincoln Laboratory Report ATC-223
Topic:
surveillance
R&D area:
R&D group:

Summary

Airport Surveillance Radar (ASR) manufacturers are proposing the use of non-linear FM pulse compression in their all solid state radars. However there is concern that the use of pulse compression will limit the radar's performance. High range sidelobes can cause poor performance in both target and weather detection. The theory of nonlinear FM pulse compression is derived along with a method of minimizing the sidelobes using a minimum mean square error (MMSE) technique. The results of a computer program using the MMSE technique show that very low sidelobe levels of more than 100 dB down may be achieved. These very low sidelobes are affected by filter misalignment, target Doppler, and by transmitter phase errors or stability. Curves are presented demonstrating these effects. We also show how filter misalignment can be corrected by receiver filtering. The methods presented here are general enough to be used to assess the performance of proposed non-linear FM waveform radars.
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Summary

Airport Surveillance Radar (ASR) manufacturers are proposing the use of non-linear FM pulse compression in their all solid state radars. However there is concern that the use of pulse compression will limit the radar's performance. High range sidelobes can cause poor performance in both target and weather detection. The theory...

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Obtaining low sidelobes using non-linear FM pulse compression

Coordinated radar and aircraft observations of turbulence

May 26, 1981
  |
Project Report
Author:
Melvin Labitt
Published in:
MIT Lincoln Laboratory Report ATC-108
Topic:
weather
R&D area:
R&D group:

Summary

Interim results of a program to measure and correlate radar- and aircraft-sensed turbulence in rainstorms are presented. The dissipation factor of a turbulence air mass can be measured by an aircraft and a weather radar. Comparisons are made between precipitation reflectivity and spectral width measurements as indicators of turbulence. The instrumentation and data processing procedures are described. Examples of turbulence observations made with a storm-penetrating aircraft and the weather radar are given. The relationship between the radar observations and the physical properties of the turbulence atmosphere are derived. The relationship of radar spectral width (variance) to turbulence intensity is discussed.
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Summary

Interim results of a program to measure and correlate radar- and aircraft-sensed turbulence in rainstorms are presented. The dissipation factor of a turbulence air mass can be measured by an aircraft and a weather radar. Comparisons are made between precipitation reflectivity and spectral width measurements as indicators of turbulence. The...

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Coordinated radar and aircraft observations of turbulence

Effects of common band (3500-3700 MHz) operation of geostationary satellites and the FAA limited-surveillance radar

November 9, 1979
  |
Project Report
Author:
David Karp
…
Published in:
MIT Lincoln Laboratory Report ATC-92
Topic:
surveillance
R&D area:
R&D group:

Summary

The study reported investigates the likelihood of interference by FDM/FM transmissions from geostationary satellites operating in the frequency range 3500-3700 MHz upon proposed FAA limited-surveillance radars operating in the same band. It is concluded, based upon the analysis, that the FAA limited-surveillance radars and the geostationary satellites can function in a common band, 3500-3700 MHz with only slight degradation to the radar coverage.
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Summary

The study reported investigates the likelihood of interference by FDM/FM transmissions from geostationary satellites operating in the frequency range 3500-3700 MHz upon proposed FAA limited-surveillance radars operating in the same band. It is concluded, based upon the analysis, that the FAA limited-surveillance radars and the geostationary satellites can function in...

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Effects of common band (3500-3700 MHz) operation of geostationary satellites and the FAA limited-surveillance radar

Coaxial magnetron spectra and instabilities

June 24, 1977
  |
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
  |
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

Automatic Reporting of Height (AROH) design and trade-off studies

November 1, 1976
  |
Technical Report
Author:
Lincoln Cartledge
…
Published in:
MIT Lincoln Laboratory Report TN-1976-42
Topic:
air traffic control
R&D area:
R&D group:

Summary

Application of MTD signal processing and state-of-the-art data processing can result in a completely automatic nodding beam height finder. The resulting savings in manpower are significant. Calculations show that such a system should have good sensitivity and adequate rejection of ground and weather clutter. Modification of an FPS-6 radar for this purpose is discussed.
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Summary

Application of MTD signal processing and state-of-the-art data processing can result in a completely automatic nodding beam height finder. The resulting savings in manpower are significant. Calculations show that such a system should have good sensitivity and adequate rejection of ground and weather clutter. Modification of an FPS-6 radar for...

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Automatic Reporting of Height (AROH) design and trade-off studies

New techniques applied to air-traffic control radars

June 1, 1974
  |
Journal Article
Author:
Charles E. Muehe
…
Published in:
Proc. IEEE, Vol. 62, No. 6, June 1974, pp. 716-723.
Topic:
air traffic control
R&D area:
R&D group:

Summary

During the past two years a program has been carried out to show how new techniques can greatly improve the performance of radars used for air-traffic control. A survey of problems associated with presently used radars was undertaken. This survey indicates that primary radar in an automated air-traffic control system can be made significantly more effective by the use of new techniques. The radar's handling of extraneous reflections (clutter) is critical to its performance. Three types of interfering clutter were found to predominate: ground clutter, weather clutter, and angels. Angels are generally accepted to be radar returns from flocks of birds. In addition, second-time-around clutter is often troublesome. For each type of clutter, all known remedies for improving the signal-to-clutter ratio were studied and radar systems were configured using appropriate sets of remedies. Some specific solutions incorporated in the resulting radar systems are: a) the use of linear large dynamic range, near-optimum digital signal processors to filter signals from clutter, b) the use of electronically step-scanned antennas to improve the correlation of aircraft and clutter returns from pulse to pulse, c) the use of multiple PRF's instead of staggered PRF's together with coherent transmitters to keep second-time-around clutter returns well correlated while still overcoming blind speeds, d) the use of a fine grained ground clutter map to give superclutter visibility on tangential targets, and e) the use of lower operating frequencies to greatly reduce weather and angel returns. Two demonstration radar systems have been implemented, an S-band radar using a mechanically rotating antenna and a UHF radar using an electronically step-scanned cylindrical antenna. Experimental results are described.
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Summary

During the past two years a program has been carried out to show how new techniques can greatly improve the performance of radars used for air-traffic control. A survey of problems associated with presently used radars was undertaken. This survey indicates that primary radar in an automated air-traffic control system...

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New techniques applied to air-traffic control radars

Concepts for improvement of airport surveillance radars

February 26, 1973
  |
Project Report
Author:
Charles E. Muehe
…
Published in:
MIT Lincoln Laboratory Report ATC-14
Topic:
radar
R&D area:
R&D group:

Summary

This report reviews the performance of operational ASR's, discusses each type of clutter with which the target must compete, examines presently employed methods of overcoming clutter and several state-of-the-art techniques which have not found their way into the ASR's for one reason or another. It concludes by describing two radars, one at S-band and one at UHF, which are believed to come closest to fulfilling ASR requirements in advanced ARTS facilities. The major improvements in performance will be derived from the use of linear optimum signal processing. Further gains will be achieved through the use of adaptive thresholds. STC will combat bird clutter. The radar will incorporate proper shaping of the antenna pattern so that aircraft off the peak of the antenna elevation beam will not be at a disadvantage compared to moving clutter at the peak. The recommended radar concepts also include radial velocity determination by Doppler measurement. This should prove of value in maintaining target tracks and in discrimination against ground vehicles.
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Summary

This report reviews the performance of operational ASR's, discusses each type of clutter with which the target must compete, examines presently employed methods of overcoming clutter and several state-of-the-art techniques which have not found their way into the ASR's for one reason or another. It concludes by describing two radars...

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Concepts for improvement of airport surveillance radars

An experimental UHF ground surveillance radar, volume II

October 12, 1972
  |
Technical Report
Author:
Lincoln Cartledge
…
Published in:
MIT Lincoln Laboratory Report TR-497-II
Topic:
radar
R&D area:
R&D group:

Summary

This is Volume 2 of the final report summarizing two years of work on ground-based foliage-penetration radar. The design and implementation of a breadboard radar system and of a theoretical and experimental investigation of target and propagation phenomena specific to the foliage-penetration problem are described. Volume 1 comprises three main sections: a short introduction; an overall description of the radar; and detailed descriptions of the hardware and software subsystems in the radar. Volume 2 describes the use of the radar as a measurements system for studying targets and the clutter environment, in addition to its use for demonstrating the feasibility of radar detection of walking men in foliage. Investigations of target return spectra, clutter return spectra, and clutter return amplitude statistics are reported. Theoretical models relating clutter spectra to wind turbulence and tree resonances are presented and compared with experimental results. Similarly, a previous theoretical prediction of target return spectra is compared with experimental results. Clutter return amplitude statistics are measured and found to be Gaussian under certain conditions. Finally, Vol.2 contains some comments on the relationships between the subclutter visibility and various parameters of digital MTI systems.
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Summary

This is Volume 2 of the final report summarizing two years of work on ground-based foliage-penetration radar. The design and implementation of a breadboard radar system and of a theoretical and experimental investigation of target and propagation phenomena specific to the foliage-penetration problem are described. Volume 1 comprises three main...

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An experimental UHF ground surveillance radar, volume II
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