Abstract: In a demodulator for demodulating a phase difference modulated microwave frequency signal, which demodulator includes a time delay element, a phase shifting unit connected in series with the time delay element, the series arrangement of the time delay element and phase shifting unit being connected to conduct the phase difference modulated signal, and two phase detectors each having one input connected to directly receive the phase difference modulated signal and its other input connected to receive that signal after it has passed through the time delay element and phase shifting unit, each phase detector includes two high sensitivity diodes having their outputs isolated from one another and two separate operating resistors each connected to only a respective one of the diodes, and the time delay element is constituted by a low loss waveguide filter.