Publications
A summary of the DABS transponder design/cost studies
March 1, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-27
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Summary
One of the major concerns in the DABS development program has been the cost of the DABS transponder. In order to realistically assess the impact on transponder cost of the many alternative techniques and design choices being considered for DABS, four study contracts were awarded to avionics manufacturers to design and estimate costs of special circuitry (in Phase I) and complete transponders (in Phase II). This report summarizes the major results of these design/cost studies, which cover general aviation, military, and air carrier transponder designs (including a retrofit kit for the military APX-72 transponder). The transponder design/cost studies have had a marked influence on the design of the DABS signal and message formats. Since the cost studies were basically intended for comparing link options for DADS, the transponder specifications used in these cost studies do not correspond in detail to current DABS transponder specifications. Therefore the cost data contained in this report cannot be taken to be completely representative of the cost of the finally specified DABS transponders.
Summary
One of the major concerns in the DABS development program has been the cost of the DABS transponder. In order to realistically assess the impact on transponder cost of the many alternative techniques and design choices being considered for DABS, four study contracts were awarded to avionics manufacturers to design...
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Technical Assessment of Satellites for CONUS Air Traffic Control, Volume II - Random Access Aircraft-To-Satellite Techniques
February 28, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-26,II
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Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST), and 3) Satellite-to-Aircraft Techniques (SAT). A technical assessment is made of the various techniques with no one particular technique emerging as superior; several feasible alternatives are identified. The assessment indicates that satellite bases techniques for CONUS ATC can be developed without relying on high risk technology. This volume deals with RAST, CAST and SAT are treated in companion volumes. A system employing RAST could operate by having each aircraft transmit a unique signature periodically, without any coordination of transmissions. The position of the aircraft is then obtained by multilateration using the arrival times of its signature at four or more satellites. Since aircraft transmissions are not coordinated, there is the possibility that different signatures may overlap at a satellite receiver. The resulting mutual interference is a factor in the performance of systems employing RAST. The critical technical aspects of RAST are explored with special emphasis on signaling formats, satellite coverage issues, degradation due to mutual interference and susceptibility to jamming.
Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST)...
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Summary of results of antenna design cost studies
February 19, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-22
Summary
Design/cost studies on antenna systems for DABS have been carried out by Texas Instruments and Westinghouse under Lincoln Laboratory sponsorship. For independent, mechanically-rotating systems aperture widths between 10' and 35' and heights between 4' and 16' were considered, with estimated corresponding production costs ranging from $10K to more than $200K. No generally-recommended implementation emerged although the trend was to choose planar arrays for stringent performance requirements and to accept less expensive reflectors when requirements were sufficiently relaxed. Although the aperture size was found to have a significant cost impact on the remainder of the system (pedestal, drive, tower), the antenna usually accounted for less than half of the total antenna installation cost. With the use of off-boresight monopulse direction-finding, agile beam arrays require only slightly more than one beam position per beamwidth. Even with the resulting simplification in the beamforming circuitry, their cost is about twice that of comparable rotators and starts at about $200K. DABS systems which share the same pedestal as primary radars ("co-located") are inherently highly constrained and tend to lead to unique implementations. For an ASR installation, an integral monopulse beacon feed constitutes an economical (less than $5K) and expedient implementation with performance parameters which, though not optimum, are acceptable for DABS (4 degrees beamwidth and 2 dB/degree elevation cut-off rate). A back-mounted antenna of the same (or smaller) aperture size as the AST reflector can also be implemented as a retrofit for about $40K. For ARSR installations, integral monopulse beacon feeds are also feasible at a very nominal cost but some performance compromises have to be accepted. Back-mounted DABS antennas can be accommodated in a large range of aperture sizes.
Summary
Design/cost studies on antenna systems for DABS have been carried out by Texas Instruments and Westinghouse under Lincoln Laboratory sponsorship. For independent, mechanically-rotating systems aperture widths between 10' and 35' and heights between 4' and 16' were considered, with estimated corresponding production costs ranging from $10K to more than $200K...
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Technical Assessment of Satellites for CONUS Air Traffic Control, Volume III - Satellite-To-Aircraft Techniques
February 19, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-26,III
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Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST), and 3) Satellite-to-Aircraft Techniques (SAT). A technical assessment is made of the various techniques with no one particular technique emerging as superior; several feasible alternatives are identified. The assessment indicates that satellite bases techniques for CONUS ATC can be developed without relying on high risk technology. This three-volume report is a technical assessment of all three techniques. The present volume examines satellite-to-aircraft techniques (SAT). The remaining two volumes treat CAST and RAST. The assessment has shown that workable systems could be configured using any one of the three techniques without reliance on high risk technology. No one technique has emerged as superior. Rather several viable alternatives have been identified. All techniques appear to require more costly avionics than today's ground-based system.
Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST)...
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A system for acoustic-phonetic analysis of continuous speech
February 15, 1974
Conference Paper
Published in:
Proc. IEEE Symp. on Speech Recognition, 15-19 April 1974, pp. 54-67.
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Summary
A system for acoustic-phonetic analysis of continuous speech is being developed to serve as part of an automatic speech understanding system. The acoustic system accepts the speech waveform as an input and produces as output a string of phoneme-like units referred to as acoustic phonetic elements (APEL'S). This paper should be considered as a progress report, since the system is still under active development. The initial phase of the acoustic analysis consists of signal processing and parameter extraction, and includes spectrum analysis via linear prediction, computation of a number of parameters of the spectrum, and fundamental frequency extraction. This is followed by a preliminary segmentation of the speech into a few broad acoustic categories and formant tracking during vowel-like segments. The next phase consists of more detailed segmentation and classification intended to meet the needs of subsequent linguistic analysis. The preliminary segmentation and segment classification yield the following categories: vowel-like sound; volume dip within vowel-like sound; fricative-like sound; stop consonants, including silence or voice bar, and associated burst. These categories are produced by a deviation tree based upon energy measurements in selected frequency bands, derivatives and ratios of these measurements, a voicing detector, and a few editing rules. The more detailed classification algorithms include: 1) detection and identification of some diphthongs, semivowels, and nasals, through analysis of formant motions, positions, and amplitudes; 2) a vowel identifier, which determines three ranked choices for each vowel based on a comparison of the formant positions in the detected vowel segment to stored formant positions in a speaker-normalized vowel table; 3) a fricative identifier, which employs measurement of relative spectral energies in several bands to group the fricative segments into phoneme-like categories; 4) stop consonant classification based on the properties of the plosive burst. The above algorithms have been tested on a substantial corpus of continuous speech data. Performance results, as well as detailed descriptions of the algorithms are given.
Summary
A system for acoustic-phonetic analysis of continuous speech is being developed to serve as part of an automatic speech understanding system. The acoustic system accepts the speech waveform as an input and produces as output a string of phoneme-like units referred to as acoustic phonetic elements (APEL'S). This paper should...
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Report on DABS/ATCRBS Field Testing Program
February 13, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-31
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Summary
The purpose of this field test program was to verify laboratory measurements of the effect of DABS uplink signal formats on ATCRBS transponders. The DABS interrogations tested were: (i) a combined ATCRBS Mode A/DABS All-Call consisting of a standard Mode A interragation with an additional pulse following the P(3) pulse; (ii) a DABS uplink message transmission consisting of a P(1)-P(2) pulse pair followed by 25 microseconds of 4 megabit per second DPSK data modulation. The timing aspects of these waveforms were selected on the basis of a previous series of laboratory bench tests made in a small cross-section of the ATCRBS transponder population. The results of these field measurements performed on a larger cross-section of field operational ATCRBS transponders agree with the results of the bench testing program: The recommended DABS uplink transmissions result in an effective combined ATCRBS/DABS All-Call mode and minimum triggering of ATCRBS transponders by DABS message transmissions.
Summary
The purpose of this field test program was to verify laboratory measurements of the effect of DABS uplink signal formats on ATCRBS transponders. The DABS interrogations tested were: (i) a combined ATCRBS Mode A/DABS All-Call consisting of a standard Mode A interragation with an additional pulse following the P(3) pulse...
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The effect of phase error on the DPSK receiver performance
February 4, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-32
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Several methods of realizing a DPSK receiver use a delay line. Temperature variations cause changes in the delay which, in turn, cause errors in the phase differences between the reference and information signals. The effect of these errors on the performance of an optimum DPSK receiver is studied in this report.
Summary
Several methods of realizing a DPSK receiver use a delay line. Temperature variations cause changes in the delay which, in turn, cause errors in the phase differences between the reference and information signals. The effect of these errors on the performance of an optimum DPSK receiver is studied in this...
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Technical Assessment of Satellites for CONUS Air Traffic Control, Executive Summary
January 31, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-26
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Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST), and 3) Satellite-to-Aircraft Techniques (SAT). A technical assessment is made of the various techniques with no one particular technique emerging as superior; several feasible alternatives are identified. The assessment indicates that satellite bases techniques for CONUS ATC can be developed without relying on high risk technology. This volume summarizes the results of a technical assessment of all three techniques. The detailed assessment is presented in companion volumes. The assessment has shown that workable systems could be configured using any one of the three techniques without reliance on high risk technology. No one technique has emerged as superior. Rather several viable alternatives have been identified. All techniques appear to require more costly avionics than today's ground-based system.
Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST)...
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Technical Assessment of Satellites for CONUS Air Traffic Control, Volume I - Coordinated Aircraft-To-Satellite Techniques
January 31, 1974
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-26,I
Topic:
R&D area:
Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST), and 3) Satellite-to-Aircraft Techniques (SAT). A technical assessment is made of the various techniques with no one particular technique emerging as superior; several feasible alternatives are identified. The assessment indicates that satellite bases techniques for CONUS ATC can be developed without relying on high risk technology. This volume deals with CAST, RAST and SAT are treated in companion volumes. A system employing CAST could operate by having each aircraft transmit only in response to interrogation from a satellite. The position of the aircraft is then obtained by multilateration using the arrival times of its response at coordinating the interrogations, mutual interference between different response can be avoided. The critical technical aspects of CAST are explored with special emphasis on signaling formats, avionics, the satellite antenna and susceptibility to jamming.
Summary
A number of satellite system techniques have been suggested as candidates to provide ATC surveillance, communication, and/or navigation service over CONUS. All techniques perform postion determination by multilateration using a constellation of satellites. They can be categorized as follows: 1) Coordinated Aircraft-to-Satellite Techniques (CAST), 2) Random Access Aircraft-to-Satellite Techniques (RAST)...
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Morphology of ionospheric scintillation
January 30, 1974
Conference Paper
Published in:
Proc. AIAA 12th Aerospace Sciences Mtg., 30 January - 1 February 1974, pp. 1-16.
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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.
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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