HF arrangement

Claim 1

A coherent radar comprising a transmitting tube, in particular a magnetron, a modulator for driving the magnetron in order to generate and transmit HF-pulses, a stable local oscillator for producing an intermediate frequency signal by mixing its output signal with echo pulses caused by the transmitted pulses, which intermediate frequency signal has a frequency which corresponds to the difference between the stable local oscillator frequency and the frequency of the transmitted pulses, and an oscillator operating at an intermediate frequency the output signal of which is led to a phase sensitive detector together with the intermediate frequency signal obtained by the mixing in order to detect the echo pulse and to generate a signal containing information about the mutual phase position between transmitted and received HF-signals, characterized in that a signal derived from the stable local oscillator is fed to the tuning cavities of the magnetron, at least in the moment of transmission, and that the modulator and the intermediate frequency oscillator are mutually time controlled in such manner that the leading edge of the modulator pulse and thereby the magnetron pulse always appears at a predetermined phase position of the output signal of the intermediate frequency oscillator.