An FM/CW method for the measurements of time delays of large Cassegrain antennas

摘要

An FM/CW measurement technique which utilizes the time domain principle was developed to measure the time delays of large Cassegrain antennas. Measured primary path delays of 60 ns (or greater) typically agreed with calculated delays to within 3 ns. Multipath sources generated within the antenna optics region were identified. The FM/CW technique in conjuction with the horn-on-dish configuration proved to be the most rapid, convenient, and accurate method for calibrating absolute time delays for a large antenna. The FM/CW instrumentation was invaluable as a diagnostics tool and facilitated increased understanding of the mechanisms of multipath signal generation within the antenna optics media multipath signals that could be deleterious to accuracy of antenna time delay calibrations.