1,141,410. Pulse doppler radar. MARCONI CO. Ltd. 24 Oct., 1967 [25 Jan., 1967], No. 3832/67. Heading H4D. The Specification describes a coherent pulsed doppler radar comprising a transmitting microwave oscillator 1 having a radio-frequency resonant circuit. The oscillator is pulsed by source 2 and the microwave pulses are fed via circulator 3 and duplexer 4 to a mixer 6 where they are converted into intermediate-frequency signals by the output of local oscillator 7. Sufficient amount of the local oscillator output is fed via coupler 9 and circulator 3 to the resonant circuit of the oscillator 1 to produce injection phase priming thereof. The operating frequency of the oscillator 1 is equal to the local oscillator frequency plus or minus the intermediate frequency. Thus at the start of each pulsing of the oscillator 1, the output of the oscillator is locked in phase with the output of the local oscillator 7. As the power output of the oscillator 1 increases, its frequency reverts to its operating value. The transmitted pulses are thus coherent. The microwave oscillator may be of the Gunn diode type.
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