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Optimum time-varying FIR filter designs for the Airport Surveillance Radar wind shear processor

December 28, 1994
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Project Report
Author:
Edward S. Chornoboy
Published in:
MIT Lincoln Laboratory Report ATC-191
Topic:
wind shear
R&D area:
R&D group:

Summary

We have developed new design algorithms for finite impulse response (FIR) filters that compensate for arbitrary input spacing and that allow for arbitrary group delay specification. The potential of these new designs to work with the ASR-9 staggered pulse spacing is examined in the context of the ASR-9 wind-shear processor (WSP). Benefits derived from the new designs include an improved (optimal) stopband design, an increased yield in pulse samples for moments estimation, and the retention of pulse-stagger phase information, which can be used for velocity dealiasing. These improvements are demonstrated using simulated and test-bed data, the latter acquired during 1991/1992 Orlando operations. Filter utilization, in the context of a pre-existing adaptive selection scheme (1) and the Orlando (FL) clutter environment, is examined using the new filters, and areas for improvement are identified.
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Summary

We have developed new design algorithms for finite impulse response (FIR) filters that compensate for arbitrary input spacing and that allow for arbitrary group delay specification. The potential of these new designs to work with the ASR-9 staggered pulse spacing is examined in the context of the ASR-9 wind-shear processor...

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Optimum time-varying FIR filter designs for the Airport Surveillance Radar wind shear processor

Safety analysis of the Traffic Information Service

November 22, 1994
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Project Report
Author:
Divya C. Chandra
…
Published in:
MIT Lincoln Laboratory Report ATC-226
Topic:
collision avoidance
R&D area:
R&D group:

Summary

Traffic Information Service (TIS) is a Mode S data link application being developed for use by general aviation (GA) pilots. Its purpose is to provide a low-cost means of assisting the pilot in visual acquisition of nearby aircraft. The service provides two functions: traffic alerting and threat assessment. These functions are also performed by the Traffic Alert and Collision Avoidance System (TCAS). The purpose of this report is to evaluate the effectiveness and safety of TIS in relation to that of TCAS I. The analysis begins with a conceptual review of Andrews' statistical model of visual acquisition. Next, the surveillance systems and threat-detection logic of TIS and TCAS I are reviewed. Results of a Monte Carlo simulation that modeled the threat-assessment performance of TCAS I and TIS are also presented. The analysis supports the conclusion that, because of the high degree of similarity between TIS and TCAS I, TIS is a safe and effective means of assisting the pilot in visual acquisition of air traffic.
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Summary

Traffic Information Service (TIS) is a Mode S data link application being developed for use by general aviation (GA) pilots. Its purpose is to provide a low-cost means of assisting the pilot in visual acquisition of nearby aircraft. The service provides two functions: traffic alerting and threat assessment. These functions...

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Safety analysis of the Traffic Information Service

Obtaining low sidelobes using non-linear FM pulse compression

November 4, 1994
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Project Report
Author:
Melvin Labitt
Published in:
MIT Lincoln Laboratory Report ATC-223
Topic:
surveillance
R&D area:
R&D group:

Summary

Airport Surveillance Radar (ASR) manufacturers are proposing the use of non-linear FM pulse compression in their all solid state radars. However there is concern that the use of pulse compression will limit the radar's performance. High range sidelobes can cause poor performance in both target and weather detection. The theory of nonlinear FM pulse compression is derived along with a method of minimizing the sidelobes using a minimum mean square error (MMSE) technique. The results of a computer program using the MMSE technique show that very low sidelobe levels of more than 100 dB down may be achieved. These very low sidelobes are affected by filter misalignment, target Doppler, and by transmitter phase errors or stability. Curves are presented demonstrating these effects. We also show how filter misalignment can be corrected by receiver filtering. The methods presented here are general enough to be used to assess the performance of proposed non-linear FM waveform radars.
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Summary

Airport Surveillance Radar (ASR) manufacturers are proposing the use of non-linear FM pulse compression in their all solid state radars. However there is concern that the use of pulse compression will limit the radar's performance. High range sidelobes can cause poor performance in both target and weather detection. The theory...

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Obtaining low sidelobes using non-linear FM pulse compression

Energy onset times for speaker identification

November 1, 1994
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Journal Article
Author:
Thomas F. Quatieri
…
Published in:
IEEE Signal Process. Lett., Vol. 1, No. 11, November 1994, pp. 160-162.
Topic:
speaker recognition
R&D area:
R&D group:

Summary

Onset times of resonant energy pulses are measured with the high-resolution Teager operator and used as features in the Reynolds Gaussian-mixture speaker identification algorithm. Feature sets are constructed with primary pitch and secondary pulse locations derived from low and high speech formants. Preliminary testing was performed with a confusable 40-speaker subset from the NTIMIT (telephone channel) database. Speaker identification improved from 55 to 70% correct classification when the full set of new resonant energy-based features were added as an independent stream to conventional mel-cepstra.
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Summary

Onset times of resonant energy pulses are measured with the high-resolution Teager operator and used as features in the Reynolds Gaussian-mixture speaker identification algorithm. Feature sets are constructed with primary pitch and secondary pulse locations derived from low and high speech formants. Preliminary testing was performed with a confusable 40-speaker...

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Energy onset times for speaker identification

GPS-squitter experimental results

October 30, 1994
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Conference Paper
Author:
Robert E. Boisvert
…
Published in:
13th AIAA/IEEE Digital Avionics Systems Conf., 30 October - 3 November 1994, pp. 521-527.
Topic:
airborne surveillance
R&D area:
R&D group:

Summary

GPS-Squitter is a system concept that merges the capabilities of Automatic Dependent Surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permits equipped aircraft to participate in ADS or beacon ground environments. This offers many possibilities for transition from beacon to ADS-based surveillance. This paper briefly defines the GPS-Squitter concept and its principal applications. The thrust of the paper is the presentation of surface and airborne surveillance measurements made at Hanscom Field in Bedford, Massachusetts and at the Logan International Airport in Boston. In each case the measurements show the excellent surveillance performance provided by this concept.
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Summary

GPS-Squitter is a system concept that merges the capabilities of Automatic Dependent Surveillance (ADS) and the Mode S beacon radar. The result is an integrated concept for seamless surveillance and data link that permits equipped aircraft to participate in ADS or beacon ground environments. This offers many possibilities for transition...

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GPS-squitter experimental results

Formant AM-FM for speaker identification

October 25, 1994
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Conference Paper
Author:
Charles R. Jankowski Jr
…
Published in:
Proc. IEEE-SP Int. Symp. on Time-Frequency and Time-Scale Analysis, 25-28 October 1994, pp. 608-611.
Topic:
speaker recognition
R&D area:
R&D group:

Summary

The performance of systems for speaker identification (SID) can be quite good with clean speech, though much lower with degraded speech. Thus it is useful to search for new features for SID, particularly features that are robust over a degraded channel. This paper investigates features that are robust over a degraded channel. This paper investigates features that are based on amplitude and frequency modulations of speech formants. Such modulations are measured using a high-resolution energy operator and related algorithms for recovering amplitude and frequency from an AM-FM signal. When these features are added to traditional features using an existing SID system with a telephone speech database, SID performance improved by as much as 15%. Energy onset time measurements that yielded improved SID performance are also discussed.
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Summary

The performance of systems for speaker identification (SID) can be quite good with clean speech, though much lower with degraded speech. Thus it is useful to search for new features for SID, particularly features that are robust over a degraded channel. This paper investigates features that are robust over a...

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Formant AM-FM for speaker identification

Summer 1992 Terminal area-Local Analysis and Prediction System (T-LAPS) evaluation

October 7, 1994
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Project Report
Author:
Steven R. Finch
…
Published in:
MIT Lincoln Laboratory Report ATC-218
Topic:
sensors
R&D area:
R&D group:

Summary

The Integrated Terminal Weather System (ITWS) is a development program initiated by the Federal Administration (FAA) to produce a fully automated, integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service sensors as well as from aircraft in flight in the terminal area. The ITWS will provide Air Traffic personnel with products that are immediately usable without further meteorological interpretation. Among the products are current terminal area weather, short-term (0-30 minute) predictions of significant weather phenomena, and the Terminal Winds product. The terminal winds product is the component of the ITWS which produces estimates of the horizontal winds on a three dimensional grid of points encompassing an airport terminal region. It uses information from a variety of sensors, including Doppler weather radars. In 1992, an operational test of an initial prototype Terminal Winds system was conducted at the MIT Lincoln Laboratory testbed in Orlando, FL. This report describes our evalution of the initial Terminal Winds prototype.
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Summary

The Integrated Terminal Weather System (ITWS) is a development program initiated by the Federal Administration (FAA) to produce a fully automated, integrated terminal weather information system to improve the safety, efficiency and capacity of terminal area aviation operations. The ITWS will acquire data from FAA and National Weather Service sensors...

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Summer 1992 Terminal area-Local Analysis and Prediction System (T-LAPS) evaluation

Experimental evaluation of features for robust speaker identification

October 1, 1994
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Journal Article
Author:
Douglas A. Reynolds
Published in:
IEEE Trans. Speech Audio Process., Vol. 2, No. 4, October 1994, pp. 639-643.
Topic:
speaker recognition
R&D area:
R&D group:

Summary

This correspondence presents an experimental evaluation of different features and channel compensation techniques for robust speaker identification. The goal is to keep all processing and classification steps constant and to vary only the features and compensations used to allow a controlled comparison. A general, maximum-likelihood classifier based on Gaussian mixture densities is used as the classifier, and experiments are conducted on the King speech database, a conversational, telephone-speech database. The features examined are mel-frequency and linear-frequency filterbank cepstral coefficients, linear prediction ceptral coefficients. The channel compensation techniques examined are cepstral mean removal, RASTA processing, and a quadratic trend removal technique. It is shown for this database that performance difference between the basic features is small, and the major gains are due to the channel compensation techniques. The best "across-the-divide" recognition accuracy of 92% is obtained for both high-order LPC features and band-limited filterbank features.
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Summary

This correspondence presents an experimental evaluation of different features and channel compensation techniques for robust speaker identification. The goal is to keep all processing and classification steps constant and to vary only the features and compensations used to allow a controlled comparison. A general, maximum-likelihood classifier based on Gaussian mixture...

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Experimental evaluation of features for robust speaker identification

TDWR scan strategy implementation

September 2, 1994
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Project Report
Author:
Daniel P. Hynek
Published in:
MIT Lincoln Laboratory Report ATC-222
Topic:
radar
R&D area:
R&D group:

Summary

The Terminal Doppler Weather Radars (TDWRs) installed at major airports around the country are intended to enhance the safety of air travel by the detection and timely warning of hazardous wind shear conditions in the airport terminal area. To meet these objectives, scan strategies to efficiently cover the protected airspace were developed after extensive testing at several sites with different meteorological environments. Since the topology and geometry differ at each TDWR location, special considerations were necessary to define the specific scan sequences for each site. This report describes the criteria used to establish these scan sequences, including the determination of the lowest practicable elevation angle for each site - the "surface scan," which is used to detect microburst surface outflows, and other special scans such as the "MTS scan," which is used to illuminate the remote Moving Target Simulator (MTS).
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Summary

The Terminal Doppler Weather Radars (TDWRs) installed at major airports around the country are intended to enhance the safety of air travel by the detection and timely warning of hazardous wind shear conditions in the airport terminal area. To meet these objectives, scan strategies to efficiently cover the protected airspace...

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TDWR scan strategy implementation

Air traffic control development at Lincoln Laboratory

September 1, 1994
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Journal Article
Author:
John C. Fielding
Published in:
Lincoln Laboratory Journal, Vol. 7, No. 2, Fall 1994, pp. 147-148.
Topic:
air traffic control
R&D area:
R&D group:

Summary

Lincoln Laboratory-developed air traffic control technologies, which were described in the Fall 1989 issue of this journal, are now in operational use. These technologies include the Mode-Select beacon system, the Traffic Alert and Collision Avoidance System, the Precision Runway Monitor system, the Terminal Doppler Weather Radar, and the Moving Target Detector signal processor used in the current generation of Airport Surveillance Radars. Our newest efforts focus on utilization of the Global Positioning System for both navigation and surveillance, and on the development of automation aids for air traffic control and management.
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Summary

Lincoln Laboratory-developed air traffic control technologies, which were described in the Fall 1989 issue of this journal, are now in operational use. These technologies include the Mode-Select beacon system, the Traffic Alert and Collision Avoidance System, the Precision Runway Monitor system, the Terminal Doppler Weather Radar, and the Moving Target...

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Air traffic control development at Lincoln Laboratory
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