Abstract: The invention relates to a coherent radar comprising a magnetron (MAG), a modulator (MOD) for pulsing the magnetron, a stable local oscillator (STALO) and a mixer (B.sub.1) for producing an intermediate frequency signal of incoming echoes and an intermediate frequency oscillator (MFO) and a phase sensitive detector (D) for detecting the echo pulses and producing a so called bipolar video signal. The modulator (MOD) and the intermediate frequency oscillator (MFO) are mutually time controlled in such manner that the front flank of the modulator pulse and thereby the magnetron pulse always appears in a predetermined phase position of the output signal of the intermediate frequency oscillator. According to the invention the oscillations of the magnetron are phase locked to an external signal in two steps. This is effected by applying a signal derived from the stable local oscillator to the tuning cavities of the magnetron before triggering.

Abstract: The invention relates to a radar system comprising a transmitter with a periodically tunable HF-transmitter tube, as a magnetron with rotating tuning body, and a receiver with a mixing stage, in which echo pulses caused by transmitted radar pulses are mixed with the output signal from a local oscillator, whose frequency can be controlled. During transmission the tuning frequency of the transmitter tube is varied periodically and in an interval before triggering the local oscillator is "slaved" to the transmitter tube, so that the local oscillator frequency follows the variations in the tuning frequency. In the triggering moment the local oscillator is locked in frequency to the value prevailing in the triggering moment. According to the invention this system is combined with a frequency predicting circuit, which mainly consists of a comparator.

Abstract: The invention relates to a coherent radar comprising a magnetron (10), a modulator (12) for pulsed driving if the magnetron, a stable local oscillator (22) and mixer (20) for producing an intermedicate frequency signal of incoming echoes and an intermediate frequency oscillator (28) and phase sensitive detector (26) for detecting the echo pulses in order to generate a so called bipolar video signal. According to the invention a HF-signal derived from the stable oscillator (22) is fed to the tuning cavities of the magnetron (10), so called priming, at least in the transmission moment, and furthermore the modulator (12) and the intermediate frequency oscillator (28) are mutually time controlled in such manner that the leading edge of the modulator pulse and thereby of the magnetron pulse always appears in a given phase position of the output signal from the intermediate frequency oscillator, for example a zero passage.