Experimental Measurements of Low Angle Ground Reflection Characteristics at L- and C-Bands for Irregular Terrain

摘要

Field measurements of terrain reflection data at L band and C band have been taken during 1980 at several test sites at Hanscom airport, Fort Devens, and Camp Edwards, Massachusetts. These field data are used for (1) characterization of the L band and C band multipath environments, (2) validation of terrain multipath propagation models, and (3) assessment of TRSB elevation angle estimation performance with various aperture sizes. Conventional beamsum, maximum likelihood, and maximum entropy angular power spectral estimates have been employed as a means to characterize the multipath environment. The maximum entropy angular power spectral estimate offered highest resolution of the various multipath signals. The L-band field measurement results indicated that the terrain multipath were specular reflection with a high multipath levels. L-band M/D ratios ranging from -5 dB to 1 dB were observed in a variety of terrain conditions. At C band, diffuse ground reflection were evident at some measurement sites, especially at Camp Edwards J2 range site, where small scale terrain roughness was fairly visible. However, these C-band diffuse reflections appeared to be at fairly low levels, e.g., -15 dB to -20 dB relative to the direct signal. The C-band peak specular multipath levels of -10 dB to -2 dB were slightly lower than those of the L-band for the same terrain geometry. (rh)