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Effects of finite register length in digital filtering and the fast Fourier transform

April 20, 1972
  |
Journal Article
Author:
Alan V. Oppenheim
…
Published in:
Proceedings of the IEEE Vol. 60, No. 8, Aug 72, pp. 957-976.
Topic:
signal processing
R&D area:
R&D group:

Summary

When digital signal processing operations are implemented on a computer or with special-purpose hardware, errors and constraints due to finite word length are unavoidable. The main categories of finite register length effects are errors due to A/D conversion, errors due to roundoffs in the arithmetic, constraints on signal levels imposed by the need to prevent overflow, and quantization of system coefficients. The effects of finite register length on implementations of linear recursive difference equation digital filters, and the fast Fourier transform (FFT), are discussed in some detail. For these algorithms, the differing quantization effects of fixed point, floating point, and block floating point arithmetic are examined and compared. The paper is intended primarily as a tutorial review of a subject which has received considerable attention over the past few years. The groundwork is set through a discussion of the relationship between the binary representation of numbers and truncation or rounding, and a formulation of a statistical model for arithmetic roundoff. The analyses presented here are intended to illustrate techniques of working with particular models. Results of previous work are discussed and summarized when appropriate. Some examples are presented to indicate how the results developed for simple digital filters and the FFT can be applied to the analysis of more complicated systems which use these algorithms as building blocks.
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Summary

When digital signal processing operations are implemented on a computer or with special-purpose hardware, errors and constraints due to finite word length are unavoidable. The main categories of finite register length effects are errors due to A/D conversion, errors due to roundoffs in the arithmetic, constraints on signal levels imposed...

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Effects of finite register length in digital filtering and the fast Fourier transform

Final Report: Transponder Test Program

April 12, 1972
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Project Report
Author:
George V. Colby
…
Published in:
MIT Lincoln Laboratory Report ATC-9
Topic:
surveillance
R&D area:
R&D group:

Summary

Performance parameters of transponders installed in aircraft were measured to determine their degree of compliance with current specifications. A mobile van was outfitted with electronic test equipment which simulated the transmitter and receiver sections of a ground interrogator and which allowed measurement of transponder parameters. A horn antenna located near the aircraft under test was used to couple signals to and from the transponder. The results of measuremetns on 504 transponders installed in general aviation aircraft, 17 transponders installed in military aircraft, and 28 transponders installed in air carrier aircraft are reported. Of these, 31 general aviation, 2 military, and one air carrier transponders were inoperative. The results of measurements of reply frequency, squitter, delay, Mode C operation, dead time, P2/P1 ratio required for suppression, suppression time, framing pulse spacing, power output and sensitivity are included.
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Summary

Performance parameters of transponders installed in aircraft were measured to determine their degree of compliance with current specifications. A mobile van was outfitted with electronic test equipment which simulated the transmitter and receiver sections of a ground interrogator and which allowed measurement of transponder parameters. A horn antenna located near...

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Final Report: Transponder Test Program

A theory for optimal MTI digital signal processing, part I. receiver synthesis

February 22, 1972
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Technical Report
Author:
Robert J. McAulay
Published in:
MIT Lincoln Laboratory Report TN-1972-14-I
Topic:
air traffic control
R&D area:
R&D group:

Summary

A classical problem in radar theory is the detection of moving targets in a ground clutter plus receiver noise background. Improvements in clutter rejection have recently been made by replacing analog MTI processors by their digital equivalents as this eliminates many of the problems associated with the maintenance of the analog hardware. In an attempt to determine the ultimate improvements possible using this new technology, the MTI problem was formulated as a classical detection problem and solved using the generalized likelihood ratio test. By manipulating the likelihood ratio, the receiver could be interpreted as a clutter filter in cascade with a Doppler filter bank. The performance of the optimum receiver was evaluated in terms of the output signal-to-interference ratio and compared with well-known MTI processors. It was shown that near-optimum performance can be obtained using a sliding weighted Discrete Fourier Transform (DFT). All of the results in Part I assume uniformly spaced transmitted pulses, which, for high velocity aircraft, leads to aliasing of the target and clutter spectra and detection blind speeds. In Part II the maximum likelihood method is applied using a more general model for the non-uniformly sampled target returns. This leads to an optimum receiver that is a slightly more complicated version of the sliding weighted DFT. In addition to removing the detection blind speeds, it is found that unambiguous Doppler measurements
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Summary

A classical problem in radar theory is the detection of moving targets in a ground clutter plus receiver noise background. Improvements in clutter rejection have recently been made by replacing analog MTI processors by their digital equivalents as this eliminates many of the problems associated with the maintenance of the...

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A theory for optimal MTI digital signal processing, part I. receiver synthesis

Interrogation scheduling for the discrete address beacon system

January 24, 1972
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Project Report
Author:
Edward J. Kelly
Published in:
MIT Lincoln Laboratory Report ATC-8
Topic:
surveillance
R&D area:
R&D group:

Summary

This report is an attempt to define the interrogation scheduling problem which arised in the implementation of the discrete address beacon idea. The interfaces of this problem with other parts of the beacon system design are discussed, and several specific algorithms for scheduling are analyzed for arrays and rotating antennas.
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Summary

This report is an attempt to define the interrogation scheduling problem which arised in the implementation of the discrete address beacon idea. The interfaces of this problem with other parts of the beacon system design are discussed, and several specific algorithms for scheduling are analyzed for arrays and rotating antennas.

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Interrogation scheduling for the discrete address beacon system

An optimum surveillance radar for ATC

January 1, 1972
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Conference Paper
Author:
Herbert G. Weiss
Published in:
IEEE Electronics and Aerospace Systems Conf., EASCON, 1972.
Topic:
air traffic control
R&D area:
R&D group:

Summary

The role of surveillance radar will change as the evolving ATC system relies more heavily upon cooperative beacons, but radars will still remain as an important system element. Today's radars have major limitations for an automated ATC environment because they report unwanted targets (ground, bird, and weather clutter) and because they are expensive to operate and maintain. In addition, to minimize ground clutter, radars are usually sited relatively close to the ground and consequently their performance is not adequate to detect small, distant, low-flying aircraft. By exploiting today's digital technology and by using a completely linear signal processing system, it is now possible to obtain a major improvement in MTI performance. The Lincoln Laboratory has demonstrated a 48-db clutter improvement factor on a 15-rpm scanning S-band ASR-type radar. This clutter rejection capability is about 20 db greater than exhibited by radars now in the field. By selection of more appropriate radar parameters, still greater fixed clutter and weather rejection can be achieved.
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Summary

The role of surveillance radar will change as the evolving ATC system relies more heavily upon cooperative beacons, but radars will still remain as an important system element. Today's radars have major limitations for an automated ATC environment because they report unwanted targets (ground, bird, and weather clutter) and because...

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An optimum surveillance radar for ATC

Interim report transponder test program

September 29, 1971
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Project Report
Author:
George V. Colby
…
Published in:
Project Report ATC-5, MIT Lincoln Laboratory
Topic:
air traffic control
R&D area:
R&D group:

Summary

This report covers the work done under the first phase of a continuing program of field tests on ATCRBS transponders. Characteristic transponder parameters were measured to determine their degree of compliance with the current specifications. A mobile van was outfitted with electronic test equipment which simulated the transmitter and receiver sections of a ground interrogator and allowed measurement of transponder parameters. A horn antenna located near the aircraft under test was used to couple signals to and from the transponder. The tests were performed at nine civilian airports on transponders installed in operational general aviation aircraft. The results of the measurements on the first 96 units are reported in detail and tentative conclusions drawn.
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Summary

This report covers the work done under the first phase of a continuing program of field tests on ATCRBS transponders. Characteristic transponder parameters were measured to determine their degree of compliance with the current specifications. A mobile van was outfitted with electronic test equipment which simulated the transmitter and receiver...

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Interim report transponder test program

Concept formulation studies of the surveillance apects of the fourth generation air traffic control system

September 21, 1971
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Project Report
Author:
Adrian E. Eckberg Jr
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Published in:
MIT Lincoln Laboratory Report ATC-7
Topic:
surveillance
R&D area:
R&D group:

Summary

This report presents a first order feasibility study of four particular candidate surveillance systems for the fourth generation air traffic control system. No attempts has been made to compare these systems, rather we have chosen to examine in detail the most crucial aspects of each. This analysis has brought to light many of the features of these systems. These are detailed along with the research and development required to select the most attractive surveillance system.
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Summary

This report presents a first order feasibility study of four particular candidate surveillance systems for the fourth generation air traffic control system. No attempts has been made to compare these systems, rather we have chosen to examine in detail the most crucial aspects of each. This analysis has brought to...

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Concept formulation studies of the surveillance apects of the fourth generation air traffic control system

Concept formulation studies of the control aspects of the fourth generation air traffic control system, final report

September 15, 1971
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Project Report
Author:
John U. Beusch
…
Published in:
MIT Lincoln Laboratory Report ATC-6
Topic:
air traffic control
R&D area:
R&D group:

Summary

A concept formulation study of the control aspects of the fourth generation air traffic control system is presented. The results of this study are not strongly influenced by present-day equipment. They are influenced by certain aspects of present airspace utilization and procedures which appear necessary for the design of an effective system. The inputs to the control system design include the fourth generation air traffic demand, characteristics of fixed elements (types of aircraft, etc.), and disturbances such as weather effects. The control system which has been formulated includes flight plan generation, flow control, conformance monitoring, and collision avoidance as control functions. A baseline control system is given as a first iteration of the fourth generation system. The baseline system is defined by classifying types of airspace, conformance requirements, and required segregation of classes of flight paths. The airspace is divided into three categories: positive control air space containing only controlled aircraft, controlled (mixed) air space containing both controlled and cooperative aircraft, and uncontrolled airspace containing uncontrolled aircraft. Cooperative aircraft must be able to accept IPC co-ands as well as simplified flight plans when flying in high density retied air space. The surveillance, navigation, and communications systems complete the interacting parts of the control system. Candidate fourth generation system concepts ranging from the completely tactical to the highly strategic have been described both in this report and elsewhere. In order to characterize a proposed concept we have drawn up a list of decisions which we find must be made in the course of a flight. We then consider where these decisions are made and thereby characterize the system. The feasibility of generating conflict free flight plans is investigated with the aid of analytical models. A consideration of the factors which influence the flight planning process is presented. Use is made of a generally accepted traffic density model for the 1995 time period. The expected number of conflicts for selected routes and the distances required to resolve conflicts are evaluated. The use of aircraft performance characteristics in evaluating the effectiveness of conflict resolution maneuvers is discussed. The level of conformance necessary for conflict free flight plans is determined for each maneuver. For cases in which the required conformance was unrealistically high, it was determined that providing velocity structure in high density airspace permitted a decrease in conformance requirements. Factors which directly influence the capability of aircraft to conform to flight plans in a strategic system as well as the relevant technology areas peculiar to the implementation of conflict free flight plans are considered. The conclusions reached during this study are followed by recommendations for future work in specific areas.
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Summary

A concept formulation study of the control aspects of the fourth generation air traffic control system is presented. The results of this study are not strongly influenced by present-day equipment. They are influenced by certain aspects of present airspace utilization and procedures which appear necessary for the design of an...

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Concept formulation studies of the control aspects of the fourth generation air traffic control system, final report

Technical development plan for a discrete address beacon system, vol. II [draft]

August 19, 1971
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Project Report
Author:
Division 4
Published in:
MIT Lincoln Laboratory Report ATC-4-II
Topic:
surveillance
R&D area:
R&D group:

Summary

The Technical Development Plan for a Discrete Address Beacon System is published in two volumes. Volume I is the basic plan, while this volume (Volume II) contains a more detailed description of the 46 tasks recommended for accomplishment during Phase 1 of the development cycle. It also includes cost estimates for each task.
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Summary

The Technical Development Plan for a Discrete Address Beacon System is published in two volumes. Volume I is the basic plan, while this volume (Volume II) contains a more detailed description of the 46 tasks recommended for accomplishment during Phase 1 of the development cycle. It also includes cost estimates...

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Technical development plan for a discrete address beacon system, vol. II [draft]

Technical development plan for a discrete address beacon system, vol. I [draft]

August 6, 1971
  |
Project Report
Author:
Division 4
Published in:
MIT Lincoln Laboratory Report ATC-4-I
Topic:
surveillance
R&D area:
R&D group:

Summary

The requirement for a Discrete Address Beacon System (DABS) was highlighted by the Department of Transportation Air Traffic Control Advisory Committee to provide improved surveillance and ground-air communications in support of air traffic control automation. This document presents a technical development plan for such a system; this plan was developed in close colaboration with FAA personnel in the Office of System Engineering Management and the Systems Research and Development Service. The DABS Technical Development Plan identifies the critical issues and technical options, presents a program for their resolution, followed by the development and test of a feasibility model of the system, and suggests a management structure to coordinate and carry out the many tasks involved in the implementation of the plan.
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Summary

The requirement for a Discrete Address Beacon System (DABS) was highlighted by the Department of Transportation Air Traffic Control Advisory Committee to provide improved surveillance and ground-air communications in support of air traffic control automation. This document presents a technical development plan for such a system; this plan was developed...

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Technical development plan for a discrete address beacon system, vol. I [draft]
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