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1、Assessment of Compatibility Between Ultrawideband Devices and Selected Federal SystemsMay 22, 2001Paul C. Roosa, Jr. National Telecommunications Future L5 (1176.45+12 MHz)Study Objectives Overall Define maximum allowable UWB EIRP in the GPS restricted band that can be tolerated by GPS receivers with
2、out causing degradation to operations. Measurements Determine UWB interference thresholds at GPS receiver input for various GPS receiver architectures. Analysis Determine maximum EIRP for various GPS scenarios.Measurements Developed & coordinated plan in public meetings Establish Interference Criter
3、ia Reacquisition undesired signal level at which an abrupt increase from nominal reacquisition time is observed. Break-lock the loss of lock between GPS receiver & a GPS satellite that occurs when interfering signal reduces the carrier-to-noise level so that the GPS Rx can no longer adequately deter
4、mine pseudo-range from the satellite signal.GPS Receiver Architectures Studied Coarse Acquisition (C/A) Tracking Semi-codeless C/A code tracking employing multiple narrowly-spaced correlatorsUWB Parameters & Values Measured (32 Permutations) PARAMETERVALUEPulse Repetition Frequency (MHz)0.1, 1.0, 5.
5、0, 20.0ModulationNone, On-Off Keying, 2% Relative Dithering, 50% Absolute Dithering Gating100% On, 20% On (4 millisec on, 16 millisec offGPS Simulator & BackgroundNoise Simulated signals from 4-satellite constellation actual GPS ephemeris data on 16 Dec 99 one satellite near zenith set at minimum sp
6、ecified limit & 3 satellites near horizon set 5 dB higher. Broadband noise added (cross- correlation from other satellites) except for codeless receiver.Measurement Cases Single Entry GPS Satellite Signal + Noise + UWB Multiple Entry (Aggregate) How UWB signals add & combine in GPS Receiver 5 combin
7、ations of UWB parameters (PRF, gating, & dithering) using up to 6 UWB generatorsCategories of Interference Effects to GPS Receivers Within any receiving filter with a bandwidth narrower than the UWB signal, the output signal becomes either (as a function of the pulse repetition characteristics):oCon
8、tinuous Wave (CW) LikeoPulse Like, oroNoise LikeOperational Scenarios (Source-Path-Receiver) Developed and coordinated in public meetings GPS applications considered: Aviation Maritime Surveying Terrestrial (land-based) Total of 13 operational scenarios studiedSummary of EIRP Limits to Protect GPSInterference Effects Range of EIRP LimitsCW-like-39 to -76.9 dBm(power in single spectral line)Noise-like-28.8 to -68.6 dBm/MHzPulse-like4.7 to -65.6 dBm/MHzGraphical Summary of EIRP Limits
