Title: Pulse-type radar with modulated carrier frequency

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Abstract: A radar system emitting a recurrent sequence of n equispaced bursts of carrier frequency, varying from one burst to the next, has a transmitter including a carrier-frequency generator with a frequency-varying motor driven by a synchronizing circuit to produce a repetitive frequency pattern recurring a whole number of times in a program cycle of n pulse periods. An associated receiver includes a local oscillator whose frequency is incremented, from one pulse period to the next, by a feedback circuit comprising a modulator with inputs connected to the output of this oscillator and to a coupler picking up the instantaneous carrier frequency from the transmitter output; this modulator works into a frequency discriminator, tuned to a predetermined intermediate frequency, returning an error signal to a control input of the oscillator via a multiple integrator concurrently storing all the error signals for the several pulse periods; an adder superposes these error signals upon a monitoring signal extracted at the beginning of each pulse period from the carrier-frequency generator. The multiple integrator includes an operational amplifier with n parallel capacitors in respective feedback paths which are normally open-circuited and are sequentially connected in circuit under the control of a shift register restarted at the beginning of each program cycle. A similar multiple integrator may be inserted in an automatic-gain-control circuit for an intermediate-frequency amplifier in the output of a mixer which heterodynes the received echoes with the local-oscillator output.


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