TROPOSCATTER MULTIPATH ANALYZER.

Abstract : The use of Rake instrumentation as a sounding technique for the troposcatter multipath channel is discussed and the implementation of the Troposcatter Multipath Analyzer is described. The transmitter emits a carrier which is biphase modulated by a pseudorandom code sequence at a selectable rate between 10 and 1.25 MHz. The corresponding multipath resolution is 0.1 to 0.8 microsec. The receiver embodies a unique implementation in which video is detected corresponding to both quadrature components of the incoming signal followed by single-bit polarity sensing. Noise is added to linearize the single-bit sampling. The receiver generates ten time-shifted local copies of the transmitter pseudo-random code and cross correlates these with the sampled video to realize ten Rake taps. The integration period or data sampling rate is selectable as 1.25, 10 or 80 ms. The resultant output of the analyzer consists of samples of the quadrature Rake tape components recorded on magnetic tape for later computer processing. The Multipath Analyzer was exercised over a test path in upper New York State. The test results are presented in the form of an extensive set of three-dimensional scattering functions. These show the distribution of received power as a function of multipath delay time and Doppler frequency. The data records leading to the calculated results were collected during the late Fall of 1969. The highlights of the results are discussed. The scattering functions calculated from data recorded during movement of a cold front through the test path provide a particularly unusual set of results. (Author)