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DABS/ATCRBS transponder bench test program

November 28, 1973
  |
Project Report
Author:
Edmond R. Becotte
…
Published in:
MIT Lincoln Laboratory Report ATC-25
Topic:
surveillance
R&D area:
R&D group:

Summary

The objective of this program was the determination of the effect on ATCRBS transponders of candidate modulation schemes in DABS uplink transmissions. Bench test were conducted on twenty-two different transponder samples, including representative air carrier and general aviation transponders and a military transponder. In this report, individual test procedures are outlined, the reduced data are presented, and some conclusions regarding the selection of the DABS uplink waveforms based upon the data are given. The basis of these conclusions is a DABS design goal of generating the least possible interference to the existing ATCRBS system. In addition to performing tests whose purpose was the direct measurement of response of ATCRBS transponders to candidate DABS uplink waveforms, tests were also run to obtain other link-related characteristic, such as response to non-standard pulses. Conclusions, based upon the test performed, were the DABS signals modulated by either PSK or FSK would be demodulated by a significant fraction of ATCRBS transponders and that there are no feasible PAM pulse widths or spacings which would not be decoded by a significant fraction of ATCRBS transponders. ATCRBS transponder reply probability drops nearly to zero when the DABS message (of arbitrary modulation type) has a duration less than 30 microseconds and is preceded by ATCRBS suppressing preamble. It was further shown that the reliability of suppression al interrogation levels near MTL can be improved by increasing the peak power of the preamble relative to the message.
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Summary

The objective of this program was the determination of the effect on ATCRBS transponders of candidate modulation schemes in DABS uplink transmissions. Bench test were conducted on twenty-two different transponder samples, including representative air carrier and general aviation transponders and a military transponder. In this report, individual test procedures are...

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DABS/ATCRBS transponder bench test program

Provisional Signal Formats for the Discrete Address Beacon System

November 9, 1973
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Project Report
Author:
Paul R. Drouilhet Jr
Published in:
MIT Lincoln Laboratory Report ATC-30
Topic:
surveillance
R&D area:
R&D group:

Summary

This document specifies provisional DABS signal formats, i.e., the characteristics of the "signals-in-space"which for the DABS interrogations and replies. Also included is a discussion of the utilization of the described formats to effect the surveillance and data link communication functions for which DABS has been designed. These signal formats will be used in the design and construction of engineering development model transponders and interrogators for prototype system test and evaluation at NAFEC during Phase II of the DABS Development Program; and, with modifications resulting from this test and evaluation effort, will form the basis for the operational implementation of DABS.
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Summary

This document specifies provisional DABS signal formats, i.e., the characteristics of the "signals-in-space"which for the DABS interrogations and replies. Also included is a discussion of the utilization of the described formats to effect the surveillance and data link communication functions for which DABS has been designed. These signal formats will...

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Provisional Signal Formats for the Discrete Address Beacon System

Prediction of optical landing guidance system performance in Cat. III-a minimum weather

November 8, 1973
  |
Technical Report
Author:
David G. Kocher
Published in:
MIT Lincoln Laboratory Report TN-1973-47
Topic:
air traffic control
R&D area:
R&D group:

Summary

The feasibility of using a laser optical system to provide precision guidance for the final two miles of aircraft landing approaches in low visibility weather is examined. Since low visibility is caused most frequently by clouds and fog, approximate calculations of the optical signal, scattered light and noise are made as a function of range for various cloud and fog densities. It is concluded that with current laser technology, performance of an optical landing guidance system would be inadequate in the presence of Category III-a minimum visibility clouds and fogs.
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Summary

The feasibility of using a laser optical system to provide precision guidance for the final two miles of aircraft landing approaches in low visibility weather is examined. Since low visibility is caused most frequently by clouds and fog, approximate calculations of the optical signal, scattered light and noise are made...

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Prediction of optical landing guidance system performance in Cat. III-a minimum weather

The Discrete Address Beacon System (DABS)

November 8, 1973
  |
Conference Paper
Author:
Herbert G. Weiss
…
Published in:
IEEE Northeast Electronic Research and Engineering Mtg., NEREM, 8 November 1973.
Topic:
air traffic control
R&D area:
R&D group:

Summary

The requirement for additional automation in the air traffic control process has placed new emphasis on the need for high quality surveillance data and for a ground-to-aircraft data link. The ATCRBS beacon system has proven a valuable complement to radar because it provides the ground controller with position, identity, and altitude data that is not contaminated by ground and weather clutter. However, the growing number of beacon-equipped aircraft and ground interrogators and the inherent self-interference limitations of the ATCRBS beacon system have motivated the need for a more reliable and flexible beacon system. The 1969 the Air Traffic Control Advisory Committee recommended the development of such an improved system which they named the Discrete Address Beacon System (DABS), incorporating both surveillance and a data link. Since 1971, M.I.T. Lincoln Laboratory, under the sponsorship of the FAA, has been investigating various DABS design options.
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Summary

The requirement for additional automation in the air traffic control process has placed new emphasis on the need for high quality surveillance data and for a ground-to-aircraft data link. The ATCRBS beacon system has proven a valuable complement to radar because it provides the ground controller with position, identity, and...

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The Discrete Address Beacon System (DABS)

Empirical assessment of ATCRBS

October 31, 1973
  |
Project Report
Author:
Alan G. Cameron
…
Published in:
MIT Lincoln Laboratory Report ATC-16
Topic:
surveillance
R&D area:
R&D group:

Summary

This report discusses the operational performance of the FAA ATCRBS system, as determined from data extracted from the ARTS III digital processing system. Data was gathered from several sites including Andrews Air Force Base, (Md.), Logan International Airport (Boston, Mass.), and McCarran International Airport (Las Vegas, Nevada). Quantitative performance data, as well as discussion of the problem area and possible techniques and procedures for its solution, are provided in the areas of weak/broken targets, false targets, synchronous garble, interference, erroneous decoding, improper defruiter operation, and insufficient angular resolution. A discussion of improvements that can alleviate some of the deficiences of today's secondary radar (ATCRBS) system is included.
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Summary

This report discusses the operational performance of the FAA ATCRBS system, as determined from data extracted from the ARTS III digital processing system. Data was gathered from several sites including Andrews Air Force Base, (Md.), Logan International Airport (Boston, Mass.), and McCarran International Airport (Las Vegas, Nevada). Quantitative performance data...

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Empirical assessment of ATCRBS

Interrogation scheduling algorithms for a discrete address beacon system

October 17, 1973
  |
Project Report
Author:
Alex Spiridon
…
Published in:
MIT Lincoln Laboratory Report ATC-19
Topic:
surveillance
R&D area:
R&D group:

Summary

This report describes several scheduling algorithms that may form part of the interrogation management function of a discrete address beacon system. These include scheduling algorithms that can handle unequal message lengths and types which can schedule a message very rapidly (dynamic scheduling). The algorithms are evaluated in terms of the computation required to execute them and their packing efficiencies.
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Summary

This report describes several scheduling algorithms that may form part of the interrogation management function of a discrete address beacon system. These include scheduling algorithms that can handle unequal message lengths and types which can schedule a message very rapidly (dynamic scheduling). The algorithms are evaluated in terms of the...

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Interrogation scheduling algorithms for a discrete address beacon system

Accuracy limitations of range-range (spherical) multilateration systems

October 11, 1973
  |
Technical Report
Author:
Harry B. Lee
Published in:
MIT Lincoln Laboratory Report TN-1973-43
Topic:
surveillance
R&D area:
R&D group:

Summary

This report presents a novel procedure for determining the accuracy of range-range (or spherical) multilateration systems. The procedure is a generalization of one previously described for hyperbolic multilateration systems. A central result is a demonstration that the inverse of the covariance matrix for positional errors corresponds to the moment of inertia matrix of a simple mass configuration. The insight afforded by this fact is used to resolve a number of questions relating to accuracy. Specific questions addressed include the following: 1. How does accuracy depend upon the number of receivers? 2. How does accuracy depend upon the deployment of receivers? 3. What is the maximum accuracy that can be obtained from N receivers? How should the receivers be deployed to maximize accuracy? 4. How do altitude errors compare to horizontal errors in satellite-based systems? In ground-based systems?
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Summary

This report presents a novel procedure for determining the accuracy of range-range (or spherical) multilateration systems. The procedure is a generalization of one previously described for hyperbolic multilateration systems. A central result is a demonstration that the inverse of the covariance matrix for positional errors corresponds to the moment of...

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Accuracy limitations of range-range (spherical) multilateration systems

An optimum interference detector for DABS monopulse data editing

September 26, 1973
  |
Technical Report
Author:
Robert J. McAulay
…
Published in:
MIT Lincoln Laboratory Report TN-1973-48
Topic:
air traffic control
R&D area:
R&D group:

Summary

In the application of the Discrete Address Beacon System (DABS) concept to Air Traffic Control (ATC) surveillance, estimates of aircraft position must be made using as few replies as possible, preferably one. This requires the use of monopulse techniques. Since the beacon system provides high signal-to-noise ratios (SNR), the fundamental limitation to direction finding (DF) performance is due to externally generated interference from multipath signals and from the present Air Traffic Control Radar Beacon System (ATCRBS). Since there are many bits in any one DABS reply it should be possible to generate an accurate azimuth estimate if those that bear interference could be detected and deleted from the sample. In this report, the generalized likelihood ratio test is used to derive an optimum interference statistic. The detector performance is then analyzed in detail with respect to its dependence on SNR, interference-to-signal ratio (ISR) and on the relative phase between the target and interfering signals. It is shown that good detection performance can be obtained if the phase difference between the target and interference signals are either in- or out-of-phase.
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Summary

In the application of the Discrete Address Beacon System (DABS) concept to Air Traffic Control (ATC) surveillance, estimates of aircraft position must be made using as few replies as possible, preferably one. This requires the use of monopulse techniques. Since the beacon system provides high signal-to-noise ratios (SNR), the fundamental...

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An optimum interference detector for DABS monopulse data editing

The effects of interference on monopulse performance

August 1, 1973
  |
Technical Report
Author:
Robert J. McAulay
Published in:
MIT Lincoln Laboratory Report TN-1973-30
Topic:
air traffic control
R&D area:
R&D group:

Summary

The first and second moments of the monopulse azimuth estimates are used to characterize the estimator performance in a background of mainbeam or sidelobe multipath or ATCRBS interference. An exact expression for the bias error is obtained that not only accounts for the bias due to targets separated in azimuth but also demonstrates the effect of fading or signal cancellation. For a target signal at a 20 dB signal-to-noise ratio, it is shown that the fading effect produces negligible bias unless the signal-to-interference ratio is between ±2.5 dB. A first order expression for the variance is obtained that demonstrates that an increase in the random error will occur due to the target separation in azimuth and due to signal fades. The exact nature of the bias and variance depend strongly on the relative phase between the target and interference signals with the poorest performance being obtained at the in- and out-of-phase conditions. It is knowledge of this behavior that is essential in evaluating the idea of azimuth estimation data editing.
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Summary

The first and second moments of the monopulse azimuth estimates are used to characterize the estimator performance in a background of mainbeam or sidelobe multipath or ATCRBS interference. An exact expression for the bias error is obtained that not only accounts for the bias due to targets separated in azimuth...

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The effects of interference on monopulse performance

Recent advances in air traffic control radars

June 26, 1973
  |
Conference Paper
Author:
Charles E. Muehe
Published in:
IEEE Northeast Electronic Research and Engineering Meeting, NEREM, 8 November 1973.
Topic:
air traffic control
R&D area:
R&D group:

Summary

This paper describes recent improvements in microwave radars used for air traffic control. These improvements have been designed to increase the target-to-clutter ratio so that adaptive thresholding can be used to give a very low false alarm rate and high probability of detection even when the aircraft target is in the presence of strong clutter. Studies show that detection suffers when three types of clutter returns are strong; namely, ground clutter, weather clutter or angels. Angels have been almost universally identified as bird flocks. Under certain terrain and propagation conditions, second-time-around clutter can also be a problem. Here ground returns from the second to last transmitted pulse are received from targets beyond the nonambiguous range. These may be from mountains or from the ground when anomalous propagation conditions occur. Meaningful improvements in this class of radar can be conveniently grouped as shown in Table I. We will briefly discuss each of the three classes listed.
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Summary

This paper describes recent improvements in microwave radars used for air traffic control. These improvements have been designed to increase the target-to-clutter ratio so that adaptive thresholding can be used to give a very low false alarm rate and high probability of detection even when the aircraft target is in...

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Recent advances in air traffic control radars
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