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Morphology of ionospheric scintillation

January 30, 1974
  |
Conference Paper
Author:
Robert K. Crane
Published in:
Proc. AIAA 12th Aerospace Sciences Mtg., 30 January - 1 February 1974, pp. 1-16.
Topic:
communications
R&D area:
R&D group:

Summary

Small scale ionospheric irregularities in the F-region can cause fluctuations in the amplitude, phase, and angle of arrival of VHF. UHF, and SHF signals traversing the ionosphere. Under some conditions, the power level fluctuations or scintillations at VHF and UHF may become severe with 12 dB signal level increases and fades in excess of 30 dB being observed. Current information about the probabilities of occurrence of severe fades is derived from a number of experiments using either radio star or satellite borne sources. The measurements are generally of signal level only and have been used to calculate scintillation indices to characterize scintillation intensity. An examination of the global distribution of scintillation indices show that scintillations are of importance to communication system performance primarily in the auroral and polar regions and at night near the geomagnetic equator.
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Summary

Small scale ionospheric irregularities in the F-region can cause fluctuations in the amplitude, phase, and angle of arrival of VHF. UHF, and SHF signals traversing the ionosphere. Under some conditions, the power level fluctuations or scintillations at VHF and UHF may become severe with 12 dB signal level increases and...

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Morphology of ionospheric scintillation

Effects of airborne transponder antenna lobe switching on en route (PCD) and terminal (BDAS) beacon reply processing

January 29, 1974
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Project Report
Author:
Ernest H. Day
…
Published in:
MIT Lincoln Laboratory Report ATC-18
Topic:
antennas
R&D area:
R&D group:

Summary

The comparative performances of switching top and bottom transponder antennas versus the bottom antenna alone, in target detection by ARTS III and by PCD, were investigated in order to determine which of the two antenna configurations is preferable. A variety of military aircraft participated, performing climbouts, orbits, straight and level segments, and descents, in order to expose a wide range of aspect angles to the interrogator. Data were collected at Washington, D.C., utilizing the ATCBI at Andrews Air Force Base, and at NAFEC, utilizing the Elwood site. The frequency of occurrence of lost targets, particularly of consecutive lost targets, was found to vary considerably from one aircraft type to another. Analysis of the reduced data provides a reasonable basis, however, for concluding that, to maximize average probability of detection, the bottom antenna is better in the terminal area but switching antennas are better for En Route application. To minimize long sequences of misses which cause track loss on turns, the switching antenna appears more favorable in both flight regimes. The data also suggest that a higher probability of detection can be obtained in both environments, without incurring serious penalties, by reducing the leading edge detection thresholds.
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Summary

The comparative performances of switching top and bottom transponder antennas versus the bottom antenna alone, in target detection by ARTS III and by PCD, were investigated in order to determine which of the two antenna configurations is preferable. A variety of military aircraft participated, performing climbouts, orbits, straight and level...

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Effects of airborne transponder antenna lobe switching on en route (PCD) and terminal (BDAS) beacon reply processing

Digital signal processor for air traffic control radars

January 1, 1974
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Conference Paper
Author:
Charles E. Muehe
Published in:
Northeast Electronics Research and Engineering Meeting, NEREM, 28-31 October 1974.
Topic:
air traffic control
R&D area:
R&D group:

Summary

At a previous NEREM Meeting [1] and in a subsequent paper [2], we described the general philosophy and particular ideas which can be used to overcome the problems associated with achieving good radar detection performance in the presence of various types of clutter; ground clutter (including second-time-around returns ), weather clutter and angels (bird flocks). Recently, a digital signal processor called an MTD (Moving Target Detector) has been designed and built for application to an S-band ASR (Airport Surveillance Radar). This paper describes the MTD and presents some preliminary test results. The MTD is a special purpose hard-wired digital signal processor which is capable of processing a full 360 coverage in 1/16 nmi steps out to a nominal range of 48 nmi. The MTD was designed to provide digital radar output to an automated air traffic control system.
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Summary

At a previous NEREM Meeting [1] and in a subsequent paper [2], we described the general philosophy and particular ideas which can be used to overcome the problems associated with achieving good radar detection performance in the presence of various types of clutter; ground clutter (including second-time-around returns ), weather...

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Digital signal processor for air traffic control radars

Final report on task A surveillance and communication issues in the transition to a discrete address beacon system

December 26, 1973
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Project Report
Author:
Walter I. Wells
…
Published in:
MIT Lincoln Laboratory Report ATC-21
Topic:
surveillance
R&D area:
R&D group:

Summary

This report discusses the transition from the ATCRBS-based surveillance function with voice radio only to a DABS-based surveillance function with integral digital communication capability to support IPC and automation. Recommendations are directed toward alleviation of certain problems already evident and toward preparation for the deployment of DABS beginning in the late 1970s. An evaluation of the present ATCRBS system indicates basic adequacy in the present environment for the current mode of operation of the ATC system. The introduction of automation into the ATC system requires capability in the areas of data link and enhances surveillance reliability for automatic tracking that the DABS system will provide. On this basis it is concluded that the ATCRBS system does not need major modifications to continue its role into the DABS period at locations where the environment and operation will be similar to that presently encountered. A number of recommendations are made regarding radar where new technology can provide significantly enhanced performance at little added cost. The introduction of a digital data link provides many opportunities and challenges. Most of them associated with tactical message handling are being addressed within the DABS program but attention is called to a related set of issues for messages originating from or destined for other than ARTS or NAS (e.g., FSS).
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Summary

This report discusses the transition from the ATCRBS-based surveillance function with voice radio only to a DABS-based surveillance function with integral digital communication capability to support IPC and automation. Recommendations are directed toward alleviation of certain problems already evident and toward preparation for the deployment of DABS beginning in the...

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Final report on task A surveillance and communication issues in the transition to a discrete address beacon system

DABS/ATCRBS transponder bench test program

November 28, 1973
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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

The Discrete Address Beacon System (DABS)

November 8, 1973
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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
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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

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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