1. A Doppler radar system, wherein a phase-sensitive detector demodulates a Doppler signal derived from an incoming signal from a moving target, the detector using a reference signal of the same frequency as the Doppler signal, comprising A TRANSMITTER, A PHASE SENSITIVE DETECTOR FOR DEMODULATING A Doppler signal, TWO COHERENT INCOMING SIGNAL DETECTORS EACH FED WITH REFERENCE SIGNAL FROM THE TRANSMITTER AND VIA DIVIDED PATHS WITH THE SAME REFLECTED INCOMING SIGNALS FROM A TARGET, TWO Doppler signal feed paths, one feeding a Doppler signal from one coherent detector to the signal input of the phase sensitive detector and the other feeding a Doppler signal from the other coherent detector to the reference input of the phase sensitive detector, PHASE SHIFT MEANS CONNECTED IN THE INCOMING SIGNAL PATH TO ONE OF THE COHERENT DETECTORS FOR INTRODUCING A QUADRATURE PHASE SHIFT BETWEEN THE TWO INCOMING SIGNALS APPLIED TO THE COHERENT DETECTORS AND, FURTHER PHASE SHIFT MEANS CONNECTED IN ONE OF THE FEEDPATHS TO THE PHASE SENSITIVE DETECTOR FOR INTRODUCING A FURTHER QUADRATURE PHASE SHIFT BETWEEN THE Doppler signals fed to the phase sensitive detector, whereby UNWANTED Doppler frequency double sideband signals in the outputs of the coherent detectors due to noise modulated transmitter signals mixed with the incoming signals result in opposing signals in the output of the phase sensitive detector.