Publications
Results of L band multipath measurements at operational United States (U.S.) airports in support of the Microwave Landing System (MLS) Precision Distance Measuring Equipment (DME/P)
July 23, 1981
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-109
Summary
This report presents the results of a short duration L band multipath measurement program at five major U.S. airports (St. Louis, Tulsa, Wright Patterson Air Force Base, Philadelphia and Washington National) and one smaller airport (Quonset, RI) to better quantify the expected multipath environment for the Microwave Landing System (MLS) Precision Distance Measuring Equipment (DME/P). Specific objectives included: (1) Measurements of the principal multipath parameters (amplitude and time delay) with realistic aircraft/ground site locations at runways which had the major DME/multipath sources (large buildings) identified in previous analytical (simulation) studies. (2) Determination of whether significant DME/P multipath sources exist which had not been considered to date and (3) Comparison of the measured results with computer simulation results obtained with simplified airport models (such as have been used for DME/P system design to date). Particular emphasis was placed on the final approach region including the flare and rollout regions since these areas correspond to the most stringent DME/P accuracy requirements and, have not been utilized operationally with the current L band DME. All of the above objectives were achieved although in some cases the experimental data in the flare/rollout region was of poor quality due to low signal to noise ratio. The spatial region and time delay of specular multipath generally correlated well with expectations based on simple ray tracing. With the exception of Washington National, no significant (multipath to direct signal ratio (M/D >110 dB) multipath was encountered in operationally relevant areas which was not predicted. The quantitative predictions of the simple airport models agreed with the experimental data, although in some cases, (especially, near threshold) the measured M/D values were considerably higher than predictions.
Summary
This report presents the results of a short duration L band multipath measurement program at five major U.S. airports (St. Louis, Tulsa, Wright Patterson Air Force Base, Philadelphia and Washington National) and one smaller airport (Quonset, RI) to better quantify the expected multipath environment for the Microwave Landing System (MLS)...
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MLS Multipath Studies, Phase 3 Final Report, Volume III: Application of Models to MLS Assessment Issues, Part 2
June 8, 1981
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-88,III,PT-2
Topic:
R&D area:
R&D group:
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new approach and landing guidance system. The first two volumes of the report presented an overview of the simulation effort as well as describing in detail the propagation and MLS technique mathematical models and their validation by comparison with experimental data. In this volume, we describe the results of comparative simulations for the various MLS techniques in various scenarios and analyze in detail certain multipath performance features which were found to be significant in the scenario simulations. Simulation results are presented for several scenarios, and shadowing of the MLS azimuth by taxiing and overflying aircraft is analyzed. The remainder of the report focuses onmultipath performance factors specific to various individual techniques. These include: (1) the effects of angle data outlier tests and filtering in the TRSB receivers, (2) the effects on the DMLS system due to receiver AGC, receiver motion-induced Doppler shifts, and the use of commutated reference systems, and (3) acquisition/validation algorithms for all three techniques. The report concludes with a summary and suggestions for future work. Part I of this volume consists of Chapters I through IV; Part II contains Chapters V through VIII and the Appendices.
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new...
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MLS Multipath Studies, Phase 3 Final Report, Volume III: Application of Models to MLS Assessment Issues, Part 1
June 8, 1981
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-88,III,PT-1
Topic:
R&D area:
R&D group:
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new approach and landing guidance system. The first two volumes of the report presented an overview of the simulation effort as well as describing in detail the propagation and MLS technique mathematical models and their validation by comparison with experimental data. In this volume, we describe the results of comparative simulations for the various MLS techniques in various scenarios and analyze in detail certain multipath performance features which were found to be significant in the scenario simulations. Simulation results are presented for several scenarios, and shadowing of the MLS azimuth by taxiing and overflying aircraft is analyzed. The remainder of the report focuses on multipath performance factors specific to various individual techniques. These include: (1) the effects of angle data outlier tests and filtering in the TRSB receivers, (2) the effects on the DMLS system due to receiver AGC, receiver motion-induced Doppler shifts, and the use of commutated reference systems, and (3) acquisition/validation algorithms for all three techniques. The report concludes with a summary and suggestions for future work. Part I of this volume consists of Chapters I through IV; Part II contains Chapters V through VIII and the Appendices.
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new...
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Comparison of various elevation angle estimation techniques
July 9, 1980
Conference Paper
Published in:
Natl. Telecommunications Conf., Houston, TX, 1-4 December 1980.
Topic:
R&D area:
Summary
The angular resolution and tracking of closely spaced targets is a classical radar problem which is receiving increased attention, and terrain multipath (e.g., reflections) has long been recognized to be a principal limitation on the achievable accuracy of radar elevation trackers at low elevation angles. A variety of techniques have been proposed for improved elevation angle estimation: however, comparative analysis based on field comparable data has not been available to date. In this paper, distributions of multipath scattered power, described in a companion paper, are used to compare several elevation angle estimation techniques: (1) conventional monopulse; (2) off-boresight monopulse; (3) double null monopulse; (4) single edge processing as is used for flare processing in the Microwave Landing System; and (5) a maximum entropy technique based estimator.
Summary
The angular resolution and tracking of closely spaced targets is a classical radar problem which is receiving increased attention, and terrain multipath (e.g., reflections) has long been recognized to be a principal limitation on the achievable accuracy of radar elevation trackers at low elevation angles. A variety of techniques have...
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Experimental measurement of the low angle terrain scattering interference environment
July 9, 1980
Conference Paper
Published in:
Natl. Telecommunications Conf., Houston, TX, 30 November-4 December 1980.
Topic:
R&D area:
Summary
This paper presents the results of an experimental program to obtain a better quantitative understanding of low angle microwave propagation phenomena needed to assess the potential for improved elevation tracking performance. It has long been recognized that terrain multipath (e.g., reflections and/or shadowing) are a principal limitation on the achievable accuracy of radar elevation trackers and/or landing navigation aids at low angles; however, there has been a paucity of relevant experimental data over irregular terrain. The experimental data presented were obtained with a 26 lambda L-band array and a 57 lambda C-band array at a variety of sites in eastern Massachusetts with vegetated and/or rolling terrain. It is shown that specular reflections appear to be the predominant multipath source and these are predictable from a model based on scattering from tilted plates.
Summary
This paper presents the results of an experimental program to obtain a better quantitative understanding of low angle microwave propagation phenomena needed to assess the potential for improved elevation tracking performance. It has long been recognized that terrain multipath (e.g., reflections and/or shadowing) are a principal limitation on the achievable...
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MLS Multipath Studies, Phase 3, Volume II: Development and Validation of Model for MLS Techniques
February 7, 1980
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-88,II
Topic:
R&D area:
R&D group:
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new approach and landing guidance system. This second volume of the report presents the mathematical models and validation data for the MLS techniques which were assessed in detail by the All Weather Operations Panel of the Interational Civil Aviation Organization. The specific techniques modeled are: 1. The Time Reference Scanning Beam (TRSB) system proposed by the United States (US) and Australia, with prime emphasis on the US equipment implementation and field test data, 2. the Doppler scan (DMLS) proposed by the United Kingdom, and 3. the DME Based Landing System (DLS) proposed by the Federal Republic of Germany.
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new...
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MLS Multipath Studies, Phase 3, Volume I: Overview and Propagation Model Validation/Refinement Studies
April 25, 1979
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-88,I
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new approach and landing guidance system. This first volume of the report presents an overview of the overall simulation results as well as a description of the refined mathematical models and validation of the propagation portion of the simulation. Specific propagation topics include: 1) preliminary results for validation of models for reflections from rough and/or rising terrain based on L-band field data. 2) validation of the models for building reflections based on field measurements at a number of operational airports. 3) validation and refinement of the models for angle guidance system shadowing by obstacles such as buildings and other objects.
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new...
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PALM - a system for precise aircraft location
May 16, 1976
Journal Article
Published in:
J. of the Institute of Navigation, Vol. 23, No. 3, Fall 1976, pp. 257-261.
Summary
The Precision Altitude and Landing Monitor (PALM) is intended to provide accurate stand-alone three-dimensional position data for aircraft equipped with standard beacon transponders using ground equipment designed for low life cycle cost. The PALM program, to the present time, has focused on an experimental evaluation of the accuracy of elevation measurements. The results of these measurements have successfully validated the theoretical prediction of a 1-mrad (0.06 degree) elevation accuracy at low elevation angles. The key features in the PALM design include (1) No new avionics required, i.e., it uses standard aircraft transponder. IFPALM is used as the data base for certain ground-to-air messages, a standard VHF or DABS data link could be employed. (2) High accuracy position data, i.e., a 1-mrad rms error in elevation and in azimuth at low elevation angles. (3) Broad airspace coverage, e.g., 40 degrees in elevation, 120 degrees in azimuth (expandable to 360 degrees), and several tens of miles in range. (4) Low life cycle equipment cost, i.e., it incorporates a fixed passive receiving antenna array and a minicomputer to perform the signal processing necessary for interference rejection.
Summary
The Precision Altitude and Landing Monitor (PALM) is intended to provide accurate stand-alone three-dimensional position data for aircraft equipped with standard beacon transponders using ground equipment designed for low life cycle cost. The PALM program, to the present time, has focused on an experimental evaluation of the accuracy of elevation...
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MLS multipath studies volume II: application of multipath model to key MLS performance issues
February 25, 1976
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-63,II
Summary
This report summarizes MLS multipath work carried out at Lincoln Laboratory from March 1974 to Sept. 30, 1975. The focus of the program is the development of realistic models for 1) the multipath in representative real world environments and 2) the multipath characteristic of candidate MLS techniques. These multipath and system models are used in a comprehensive computer simulation to predict the strengths and weaknesses of major MLS systems when subjected to representative real world environments. The report is organized into two volumes. Volume I describes the algorithms and validation of various portions of the program. In Volume II, the simulation (or selected portions thereof) is applied to key multipath related MLS issues. Mathematical models are given for the major MLS multipath sources (ground reflections, building and aircraft reflections, and shadowing by objects and humped runways), and it is shown that they agree (Doppler and scanning beam) considered in phase II of the U.S. MLS program are presented together with validation by comparison with theory and bench tests. Also presented are the results of a general study in motion averaging. The (validated) computer simulation (and portions thereof) is then applied to studying 1) the critical areas required by the TRSB system to avoid excessive reflection effects, 2) the expected TRSB performance of a specific TRSB system at Friendship International Airport (MD).
Summary
This report summarizes MLS multipath work carried out at Lincoln Laboratory from March 1974 to Sept. 30, 1975. The focus of the program is the development of realistic models for 1) the multipath in representative real world environments and 2) the multipath characteristic of candidate MLS techniques. These multipath and...
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MLS multipath studies volume I: mathematical models and validation
February 25, 1976
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-63,I
Summary
This report summarizes MLS multipath work carried out at Lincoln Laboratory from March 1974 to Sept. 30, 1975. The focus of the program is the development of realistic models for 1) the multipath in representative real world environments and 2) the multipath characteristic of candidate MLS techniques. These multipath and system models are used in a comprehensive computer simulation to predict the strengths and weaknesses of major MLS systems when subjected to representative real world environments. The report is organized into two volumes. Volume I describes the algorithms and validation of various portions of the program. In Volume II, the simulation (or selected portions thereof) is applied to key multipath related MLS issues. Mathematical models are given for the major MLS multipath sources (ground reflections, building and aircraft reflections, and shadowing by objects and humped runways), and it is shown that they agree (Doppler and scanning beam) considered in phase II of the U.S. MLS program are presented together with validation by comparison with theory and bench tests. Also presented are the results of a general study in motion averaging. The (validated) computer simulation (and portions thereof) is then applied to studying 1) the critical areas required by the TRSB system to avoid excessive reflection effects, 2) the expected TRSB performance of a specific TRSB system at Friendship International Airport (MD).
Summary
This report summarizes MLS multipath work carried out at Lincoln Laboratory from March 1974 to Sept. 30, 1975. The focus of the program is the development of realistic models for 1) the multipath in representative real world environments and 2) the multipath characteristic of candidate MLS techniques. These multipath and...
READ MORE