Technique for Doppler-invariant detection in fixed-range radar and communication systems using surface-acoustic-wave devices

A scheme for a coherent fixed-range miniature radar in which surface-acoustic-wave devices are used to provide an output function insensitive to Doppler shift is described. The transmitted signal is a high-duty-cycle pulse train coded with biphase modulation according to a pseudorandom binary sequence. In the interpulse period, the total electrical quiescence of the transmitter is achieved. Receiver processing occurs during these quiescent intervals using autocorrelation followed by postdetection integration with a filter bandwidth matched to the integration time. In both transmitter and receiver the necessity for surface-acoustic-wave devices is demonstrated. Potential applications of the techniques to communications are discussed.