Suppression of stationary targets in ultrasonic appts. - using orthogonal pair of Doppler signals to suppress still or slowly moving targets

摘要

A circuit for stationary and slow-moving target suppression determines target velocity by measuring the Doppler shift between an emitted signal and the signal reflected from the target and received at the device. The received signal is amplifield and demodulated in a pair of Doppler output signals. Feedback from the demodulator outputs to the amplifier input is provided. Two phase shift circuits supplied by the demodulator outputs convert the Doppler output signals to two pairs of orthogonal signals. One of each pair is connected to one of two summers. One summer output represents the direction of motion of the target and the other the exactly opposite motion.