Browsing International Telemetering Conference Proceedings, Volume 36 (2000) by Subjects
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DYNAMIC BEHAVIOR OF MULTIPATH INTERFERENCE IN ARTM CHANNEL SOUNDING DATAData collected during July 1999 at Edwards EAFB by the Advanced Range Telemetry (ARTM) program is examined to characterize the dynamic behavior of multipath interference in an aeronautical telemetry channel. Multipath fade events are analyzed in the frequency domain to show how these fades appear, evolve, and disappear from the channel. A channel model and examples from the channel sounding data are used to show the dynamic nature of these fade events. The Doppler power spectrum is used to quantify the exact time-varying nature of the multipath fade events. The coherence time, or the amount of time the channel can be viewed as unchanging, is obtained from the Doppler power spectrum and is calculated to be 100 ms in the data sets examined in this paper. This implies that adaptive multipath mitigation techniques must have an adaptation bandwidth of 10 Hz.
THE EFFECTS OF CARRIER FREQUENCY AND ANTENNA DIAMETER ON FREQUENCY SELECTIVE MULTIPATH FADINGThis paper uses ARTM channel sounding data collected at Edwards Air Force Base to investigate the dependency between the characteristics of frequency selective multipath fading and carrier frequency and ground based received antenna diameter. Channel model parameters are obtained from data sets measured at different frequencies and various ground based antenna diameters. The analysis shows that the multipath characteristics do not statistically change between the L-band and S-band carrier frequencies, but do change with antenna diameter. Furthermore, Flight 18 data shows that antenna diversity may be a useful technique to reduce data loss from multipath fading.