Parasitic echo neutralisation system for radar - detects, filters and amplifies beat frequency caused by echo and gives alarm when beat modulation becomes irregular

摘要

A received radar signal is filtered and amplified to form a rectangular pulse of constant amplitude and with a frequency which varies, as a result of interference, caused by echos. The frequency variations are determined by counting clock pulses during each two successive periods generated by the start of the signal. The values are compared with a threshold value to re-start the sequence of events. If the value is exceeded an alarm system is initiated. The clock pulses are processed by a counter, on each group of two successive trains, by adding them or subtracting them according to the parity of the time period considered. The variations in the count are determined by a comparator.