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MLS multipath studies volume I: mathematical models and validation

February 25, 1976
  |
Project Report
Author:
James E. Evans
…
Published in:
MIT Lincoln Laboratory Report ATC-63,I
Topic:
L-band
R&D area:
R&D group:

Summary

This report summarizes MLS multipath work carried out at Lincoln Laboratory from March 1974 to Sept. 30, 1975. The focus of the program is the development of realistic models for 1) the multipath in representative real world environments and 2) the multipath characteristic of candidate MLS techniques. These multipath and system models are used in a comprehensive computer simulation to predict the strengths and weaknesses of major MLS systems when subjected to representative real world environments. The report is organized into two volumes. Volume I describes the algorithms and validation of various portions of the program. In Volume II, the simulation (or selected portions thereof) is applied to key multipath related MLS issues. Mathematical models are given for the major MLS multipath sources (ground reflections, building and aircraft reflections, and shadowing by objects and humped runways), and it is shown that they agree (Doppler and scanning beam) considered in phase II of the U.S. MLS program are presented together with validation by comparison with theory and bench tests. Also presented are the results of a general study in motion averaging. The (validated) computer simulation (and portions thereof) is then applied to studying 1) the critical areas required by the TRSB system to avoid excessive reflection effects, 2) the expected TRSB performance of a specific TRSB system at Friendship International Airport (MD).
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Summary

This report summarizes MLS multipath work carried out at Lincoln Laboratory from March 1974 to Sept. 30, 1975. The focus of the program is the development of realistic models for 1) the multipath in representative real world environments and 2) the multipath characteristic of candidate MLS techniques. These multipath and...

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MLS multipath studies volume I: mathematical models and validation

Optimum elevation angle estimation in the presence of ground reflection multipath

February 9, 1976
  |
Technical Report
Author:
Robert J. McAulay
Published in:
MIT Lincoln Laboratory Report TN-1976-11
Topic:
air traffic control
R&D area:
R&D group:

Summary

An optimal trade-off between the width of the subarray aperture and the width of the interferometer base line is performed that achieves a specified elevation angle estimation error while minimizing the overall height of the interferometer configuration. Statistical decision theory is used to analyze and design a separate sensor for resolving the interferometer ambiguities. For coverage over 2.5 to 40 in elevation and +/-60 in azimuth, two 7-wavelength subarrays separated by 8 wavelengths are sufficient for 1-mrad elevation-angle errors. A 4-element nonuniformly spaced array of dipole antennas mounted on tri-plane reflectors renders the probability of an ambiguity error less than 0.004.
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Summary

An optimal trade-off between the width of the subarray aperture and the width of the interferometer base line is performed that achieves a specified elevation angle estimation error while minimizing the overall height of the interferometer configuration. Statistical decision theory is used to analyze and design a separate sensor for...

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Optimum elevation angle estimation in the presence of ground reflection multipath

Summary of DABS antenna studies

February 3, 1976
  |
Project Report
Author:
Jean-Claude Sureau
Published in:
MIT Lincoln Laboratory Report ATC-53
Topic:
surveillance
R&D area:
R&D group:

Summary

A DBS antenna is characterized by the simultaneous availability of three beams: 1. A sum beam through which all data is transferred. 2. A monopulse difference beam used for target direction finding. 3. A control beam. Its function is to guarantee that all transactions occur in the main beam. Whereas the desirable azimuth characteristics arise from the basic required functions and from the necessity to minimize the effects of the RF (target) environment, the desirable elevation features are such as to reduce the effects of the physical environment. Implementation options are very sensitive to the type (if any) of primary radar with which it is to be collocated.
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Summary

A DBS antenna is characterized by the simultaneous availability of three beams: 1. A sum beam through which all data is transferred. 2. A monopulse difference beam used for target direction finding. 3. A control beam. Its function is to guarantee that all transactions occur in the main beam. Whereas...

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Summary of DABS antenna studies

Design validation of the network management function

February 2, 1976
  |
Project Report
Author:
Patricia H. Mann
…
Published in:
MIT Lincoln Laboratory Report ATC-54
Topic:
air traffic control
R&D area:
R&D group:

Summary

This document presents the results of a major design validation effort of the Network Management function described in the DABS Engineering Requirements document. The design validation is based on simulation of a DABS network of three sensors interacting with airborne traffic of approximately 800 aircraft
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Summary

This document presents the results of a major design validation effort of the Network Management function described in the DABS Engineering Requirements document. The design validation is based on simulation of a DABS network of three sensors interacting with airborne traffic of approximately 800 aircraft

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Design validation of the network management function

Airport survey for MLS multipath issues

December 15, 1975
  |
Project Report
Author:
David A. Shnidman
Published in:
MIT Lincoln Laboratory Report ATC-58
Topic:
air traffic control
R&D area:
R&D group:

Summary

Eight major U.S. civilian airports were visited and data on the surface material of all sizable buildings visible from the runways were obtained. This information is catalogued herein. It is only with the aid of such information that we can address issues such as the likelihood of a system performance changes due to polarization, pattern control and coverage control. A total of 93 buildings and 123 surfaces are included and the breakdown between the various surfaces is as follows: 74 surfaces were corrugated 17 surfaces were cinder block 16 surfaces were brick 9 surfaces were concrete 5 surfaces were metal. Of the 74 corrugated surfaces 18 were of the "flat" variety, 34 were one of five sub-categories and the remaining 22 needed 15 sub-categories for classification.
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Summary

Eight major U.S. civilian airports were visited and data on the surface material of all sizable buildings visible from the runways were obtained. This information is catalogued herein. It is only with the aid of such information that we can address issues such as the likelihood of a system performance...

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Airport survey for MLS multipath issues

Discrete address beacon system (DABS) test plan for FY 1976

November 14, 1975
  |
Project Report
Author:
William H. Harman III
…
Published in:
MIT Lincoln Laboratory Report ATC-56
Topic:
surveillance
R&D area:
R&D group:

Summary

The major objectives of the continued DABS testing by Lincoln Laboratory are: (1) design validation and refinement, (2) performance assessment, and (3) the development of a data base of environmental characteristics. This document describes that portion of the test activities that will take place during FY 1976. Also included is a description of the special test facilities and teclmiques needed to collect and analyze the required data.
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Summary

The major objectives of the continued DABS testing by Lincoln Laboratory are: (1) design validation and refinement, (2) performance assessment, and (3) the development of a data base of environmental characteristics. This document describes that portion of the test activities that will take place during FY 1976. Also included is...

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Discrete address beacon system (DABS) test plan for FY 1976

Logan MLS multipath experiment

September 23, 1975
  |
Project Report
Author:
David A. Shnidman
Published in:
MIT Lincoln Laboratory Report ATC-55
Topic:
air traffic control
R&D area:
R&D group:

Summary

The National Plan for a Microwave Landing System (MLS) has specified a carrier frequency for the system in the vicinity of 5.1 GHz. At that frequency, no multipath data taken at a major civilian airport existed. The purpose of this experiment was to obtain such data at Logan International Airport in order to ascertain: 1) which objects are the major causes of measurable multipath reflections and their levels relative to the direct signal (MID level), 2) whether or not the reflections from these objects can be satisfactorily simulated by the Lincoln computer model and, if so, how complicated must that model be, and 3) if the characteristics of multipath provide a significant discriminant between the Doppler and scanning beam techniques. It was found in the experiment that regions where reflections were noted could be predicted from ray optics and diffraction. No measurable reflections were noted elsewhere. For the purpose of modeling for multipath, building surfaces could be characterized as a flat plate with a reflection coefficient determined by measurement if it were a complicated surface, or by the dielectric properties of the surface material, if a simple surface. The airplane reflection model was also found to agree well with measurements.
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Summary

The National Plan for a Microwave Landing System (MLS) has specified a carrier frequency for the system in the vicinity of 5.1 GHz. At that frequency, no multipath data taken at a major civilian airport existed. The purpose of this experiment was to obtain such data at Logan International Airport...

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Logan MLS multipath experiment

DABS downlink coding

September 12, 1975
  |
Project Report
Author:
John T. Barrows
Published in:
MIT Lincoln Laboratory Report ATC-48
Topic:
surveillance
R&D area:
R&D group:

Summary

This report summarizes the encoding/decoding techniques incorporated into the DABS-downlink design. It has been determined that the binary cyclic code used for the uplink is applicable to the downlink interference environment, thus rendering considerable hardware simplification in the transponder. The downlink environment leads to a characterization as a burst erasure channel, which allows the code to be used to a burst correction capacity. This report concentrates on the error correction techniques including specific implementations. Evaluation of the performance of the code by simulation and/or bench test is presently being carried out and will be reported in a future document.
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Summary

This report summarizes the encoding/decoding techniques incorporated into the DABS-downlink design. It has been determined that the binary cyclic code used for the uplink is applicable to the downlink interference environment, thus rendering considerable hardware simplification in the transponder. The downlink environment leads to a characterization as a burst erasure...

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DABS downlink coding

DABS uplink coding

July 25, 1975
  |
Project Report
Author:
John T. Barrows
Published in:
MIT Lincoln Laboratory Report ATC-49
Topic:
surveillance
R&D area:
R&D group:

Summary

This report details the coding techniques incorporated into the DABS uplink design. Justification is given for the error control method selected in terms of the link characteristics and design constraints. Performance results, including extensive evaluation by simulation and bench test, are presented for the selected code. A binary shortened cyclic code having 24 redundant bits was selected. The overhead due to the code redundancy is minimized by a scheme in which the parity check bits are overlayed on the discrete address field in the encoded message. This code is shown to have the capability of protecting a DABS transponder from accepting an erroneous uplink message with an error probability of less than 10 to the -7 power in a severe interference environment. This same code will be used in the DABS downlink in a burst erasure correction mode. Results of the analysis of the downlink will appear in a separate report.
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Summary

This report details the coding techniques incorporated into the DABS uplink design. Justification is given for the error control method selected in terms of the link characteristics and design constraints. Performance results, including extensive evaluation by simulation and bench test, are presented for the selected code. A binary shortened cyclic...

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DABS uplink coding

Impact of obstacle shadows on monopulse azimuth estimate [project report]

July 17, 1975
  |
Project Report
Author:
Alex Spiridon
Published in:
MIT Lincoln Laboratory Report ATC-50
Topic:
surveillance
R&D area:
R&D group:

Summary

Obstacle shadows, within view of a sensor using monopulse azimuth estimate, cause an error in the azimuth estimate. This report discusses the azimuth error as a function of obstacle dimension and position, and the sensor antenna illumination.
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Summary

Obstacle shadows, within view of a sensor using monopulse azimuth estimate, cause an error in the azimuth estimate. This report discusses the azimuth error as a function of obstacle dimension and position, and the sensor antenna illumination.

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Impact of obstacle shadows on monopulse azimuth estimate [project report]
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