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effect on sensor performance.
TMF's initial operation and testing took place at Lincoln Laboratory and Boston's Logan Inter-national Airport. The system was then trans-ported to Philadelphia and Washington to expe-rience the traffic and interference levels of the northeast corridor. Las Vegas, a location well known for its significant ground-bounce multi-path problem, was the next site. Final TMF measurements were made atLosAngeles, which suffers from the highest airport traffic and inter-ference levels in the United States.
Comparison of Automated Radar Terminal System with TMF
At each of the above sites, TMF data was recorded simultaneously with data from the existing FAA sensor. The data enable a direct comparison between the monopulse processing ofTMFand thecurrentAutomatedRadarTermi-nal System (ARTS) processing.
Figure 16 shows an example ofthis compari-son for data collected in Philadelphia for an area of 80 nmi by 80 nmi (13). Figure 16(a) shows ARTS data; Fig. 16(b) shows TMF data. Each pointrepresents an unsmoothed position report measured once each antennascan. The reduced measurement errors of theTMF data are readily apparent.
Orlando -The Mode S Beacon Radar System
Surveillance Performance Comparison
Table 1gives a quantitative comparison ofthe average performance of ARTS versus TMF for all of the TMF sites. The table confirms the greatly improved qualitative performance seen in Fig. 16.
The Lincoln Laboratory Journal. Volume 2. NlLmber 3 (J 989)
Table 1. Surveillance Performance Comparison
Arts TMF Monopulse
All Crossing All Crossing
Blip/Scan Azimuth Error (1 a) Range Error (1 a) 94.6% 0.16° 124 ft 86.9% 98.0% 0.04° 24 ft 96.6%
In the table, the blip/scan ratio is the proba-bility that the system will generate a target report for a specific aircraft on a given scan. When all aircraft are considered, the blip/scan ratio is 94.6% for ARTS and 98.0% forTMF. The most significant difference in blip/scan per-formance is revealed when only crossing tracks are considered. Crossing tracks are cases in which aircraft are close enough to present a possible synchronous garbling problem. For this subset of aircraft, the blip/scan ratio for ARTS dropped to 86.9%, while the performance of TMF remained at 96.6%. This result clearly indicates thebenefitofmonopulse processingin resolving garbled replies.
Monopulse processing was also responsible for the TMF's substantially smaller measured-azimuth error of 10" = 0.04°. Furthermore, the 1-0" range error for TMF was more than five times less because of an improvement in mea-suring the time of arrival of replies.
Engineering-Model Sensors
A major step in validating the Mode-S design occurred in 1975 when the FAA awarded Texas Instruments a contract for the development of three engineering-model sensors. In 1977, Texas Instruments delivered the three sensors to the FAA Technical Center for extensive field evaluation. Figure 17isa drawingofoneofthose sensors.
Aircraft Reply and Interference Environment Simulator (ARIES)
The engineering-model sensors were built to demonstrate a sensor with the capacity to handle a maximum of400 aircraft in 360°, and apeakof50aircraftina sectorof11.5°. Capacity tests ofthese sensors could not be accomplished with real ATCRBS aircraft because an aircraft density ofsuch magnitude did not exist. even in the highest densities of Los Angeles. Further-more, only a small number ofMode-S transpon-ders were available.
Fig. 17-Mode-S engineering-model sensor. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：The Mode S Beacon Radar System(9)
