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A theory for optimal MTI digital signal processing, part II. signal design

Published in:
MIT Lincoln Laboratory Report TN-1972-14-II

Summary

In Part I of this report the optimum MTI receiver was derived and analyzed for the case in which the radar pulses were emitted from the transmitter equally spaced in time. For typical long range ATC surveillance radars , aliasing of the target and clutter spectra results in detection blind speeds at multiples of approximately 70 knots. It is well known operationally that these blind speeds can be eliminated by staggering the transmitter PRF. Heretofore, there has been no thorough theoretical analysis of the effect of staggered PRF on the spectral distribution of the target and clutter signals. It is shown in Part II that the clutter spectral density continues to fold over at the PRF, but that the signal spectrum becomes dispersed in frequency, somewhat like an anti-jam signal. The effect that this phenomenon has on the performance of the optimum processor is evaluated in terms of the signal-to-interference ratio (SIR) criterion that was derived in Part I. It is further noted that even when the target Doppler shifts are more than one PRF apart, the spectra are distinguishable, suggesting that unambiguous Doppler estimation may be possible. This concept is explored in detail using the MTI ambiguity function. It is shown that good SIR performance can be obtained by choosing the stagger parameters to minimize the height of the subsidiary Doppler side-lobes. The resulting design problem is noted to be similar to that of obtaining good antenna patterns for arrays having non-uniformly spaced elements.
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Summary

In Part I of this report the optimum MTI receiver was derived and analyzed for the case in which the radar pulses were emitted from the transmitter equally spaced in time. For typical long range ATC surveillance radars , aliasing of the target and clutter spectra results in detection blind...

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Dual lane runway study, interim report, Project 082-421-214

Published in:
Project Report ATC-11, MIT Lincoln Laboratory

Summary

An overview of the issues involved in the design of dual lane runways is presented. These issues include: centerline spacing, parallel taxiway, high speed exits, midpoint versus end point crossing, threshold stagger, and departure/arrival runway preference. An interactive graphics simulation was developed on the TX-2 computer. The simulation provides the capability for an airport designer to easily input dual lane runway configurations. ATC controllers were employed for over 100 hours to control and direct simulated traffic to various dual lane configurations. A set of preliminary criteria for dual lane runway configurations are presented along with recommendations for future work.
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Summary

An overview of the issues involved in the design of dual lane runways is presented. These issues include: centerline spacing, parallel taxiway, high speed exits, midpoint versus end point crossing, threshold stagger, and departure/arrival runway preference. An interactive graphics simulation was developed on the TX-2 computer. The simulation provides the...

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Comparison of immunity to garbling for three candidate modulation schemes for DABS

Published in:
MIT Lincoln Laboratory Report ATC-12

Summary

The performance of three candidate modulation schemes for DABS is analyzed in this report and a comparison on the basis of probability of error per bit is made. The three types of modulation are PAM, DPSK, and FSK. The results show that, at a given level of interference and signal-to-noise ratio, DPSK and FSK have a lower P(e)/bit than PAM and this difference is significant in most cases. In addition to P(e)/bit, however, the choice of modulation and message format depends on the capacity required, bandwidth occupancy, and cost of implementation. This list consideration is especially important with regard to the transponder.
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Summary

The performance of three candidate modulation schemes for DABS is analyzed in this report and a comparison on the basis of probability of error per bit is made. The three types of modulation are PAM, DPSK, and FSK. The results show that, at a given level of interference and signal-to-noise...

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Parallel approach surveillance

Published in:
MIT Lincoln Laboratory Report ATC-13

Summary

This report investigates the requirements imposed on a surveillance system for supporting independent approaches to closely spaced parallel runways. Based on a proposed procedure for monitoring aircraft approach paths and controlling deviations from proper approach paths, the required spacing between runway centerlines is derived as a function of surveillance system characteristics and other parameters. Potential trade-offs between the surveillance system characteristics are then investigated to determine whether the DABS sensor might be utilized for position measurement and/or communication in such a surveillance system. The results indicate that the required runway spacing is more sensitive to delays and data update intervals than to position measurement accuracies, and that, if DABS is to perform the communication function in the system, it should probably be used for position measurement as well.
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Summary

This report investigates the requirements imposed on a surveillance system for supporting independent approaches to closely spaced parallel runways. Based on a proposed procedure for monitoring aircraft approach paths and controlling deviations from proper approach paths, the required spacing between runway centerlines is derived as a function of surveillance system...

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Surveillance aspects of the Advanced Air Traffic Management System

Published in:
MIT Lincoln Laboratory Report ATC-10

Summary

Three topics with impact on the performance of Air-to Satellite-to-Ground Systems for Air Traffic Control Surveillance are addressed in detail: 1) vulnerability to intentional jamming; 2) performance degradation due to the multiple access noise which results from uncoordinated aircraft transmissions, and 3) tracking techniques for improved surveillance accuracy and reduced short-term outages.
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Summary

Three topics with impact on the performance of Air-to Satellite-to-Ground Systems for Air Traffic Control Surveillance are addressed in detail: 1) vulnerability to intentional jamming; 2) performance degradation due to the multiple access noise which results from uncoordinated aircraft transmissions, and 3) tracking techniques for improved surveillance accuracy and reduced...

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Final Report: Transponder Test Program

Published in:
MIT Lincoln Laboratory Report ATC-9

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

Published in:
MIT Lincoln Laboratory Report TN-1972-14-I

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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Interrogation scheduling for the discrete address beacon system

Author:
Published in:
MIT Lincoln Laboratory Report ATC-8

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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An optimum surveillance radar for ATC

Published in:
IEEE Electronics and Aerospace Systems Conf., EASCON, 1972.

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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Interim report transponder test program

Published in:
Project Report ATC-5, MIT Lincoln Laboratory

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...

READ MORE