Secondary radar interrogation signal receiver - processes signals at various levels using sum and difference functions and HF amplifier

摘要

A system for receiving reply signals can be depicted by a two channel secondary radar receiver where the sum and difference of the received signals is produced. The summing channel receives a signal at terminal (5) from an antenna and this signal is taken to a bandpass filter, whose middle frequency lies in the region of 1090 MHZ (normal for secondary radar systems). Next follows a HF amplifier which is connected to an attenuator, then to another high frequency amplifier to which a video detector is joined, thence to a linear video amplifier, a logarithmic video amplifier and finally to a video preparation circuit. The received signal is digitalised and processed in the normal manner. The difference signal is assimilated and treated in the same manner in a similar circuit, both circuits also incorporating threshold detectors.