Fully-coherent multiple frequency radar system

Claim 2

The combination comprising a system for transmitting a plurality of mutually coherent frequencies uniformly spaced apart in frequency by a preselected spacing frequency and for receiving echoes of said transmitted frequencies, and having a spacing frequency oscillator for generating said spacing frequency; and coherent signal processing means responsive to said oscillator of said system and the beat frequencies between received echoes for providing a phase-detected receiver signal.

Claim 3

The device of claim 1 in which there is further provided doppler filter means responsively coupled to the output of said coherent processing means for suppressing that spectral content thereof which is indicative of the clutter return in a substantially clutter-referenced signal.

Claim 4

The device of claim 1 in which there is further provided moving target indicating means responsive to said coherent processing means comprising high frequency bandpass means the upper frequency limit of the bandpass of which does not exceed one-half the pulse repetition frequency of a sampled-data system utilizing said device.

Claim 5

The device of claim 1 in which said signal processing means comprises frequency mixing means responsive to said received echoes for providing an intermediate frequency signal indicative of the frequency differences therebetween; intermediate frequency means having a center frequency corresponding to an integer multiple of said spacing frequency and a bandpass limited to the reciprocal of the transmitted pulsewidth for amplifying a selected one of said beat frequencies; and a phase-sensitive detector having a first and second input respectively coupled to the output of a respective one of said spacing oscillator and intermediate frequency means.

Claim 6

A pulsed energy system including a pulse modulator, and comprising a source of a modulating frequency at least as high as that represented by the reciprocal of the pulsewidth provided by said pulsed energy system; multiple frequency generating means responsive to said modulating frequency for generating at least two mutually coherent, concomitant and discrete frequencies, spaced apart in frequency by said modulating frequency, and being modulated by said pulse modulator for transmission by said pulsed energy system; and phase sensitive detection means having a first input responsive to selected ones of the beat frequencies between received echoes of signals transmitted by said system and further having a reference input responsive to said source of a modulating frequency for providing a phase-detected output signal.

Claim 7

A pulsed energy system including a pulse modulator, and comprising a source of a modulating frequency at least as high as that represented by the reciprocal of the pulsewidth provided by said pulsed energy system; multiple frequency generating means responsive to said modulating frequency for generating at least two mutually coherent, concomitant and discrete frequencies, spaced apart in frequency by said modulating frequency, and being modulated by said pulse modulator for transmission by said pulsed energy system; and phase sensitive detection means having a first input responsive to selected ones of the beat frequencies between received echoes of signals transmitted by said system and further having a reference input responsive to said source of a modulating frequency for providing a phase-detected output signal.

Claim 8

A pulsed radar system including a pulse modulator and comprising a source of a modulating frequency at least as high as that represented by the reciprocal of the pulsewidth provided by said pulsed radar system; closed loop radio frequency single side band modulating means responsive to said modulating frequency for generating a side band signal representing at least two mutually coherent, concomitant and discrete frequencies, uniformly spaced apart in frequency by said modulating frequency, said side band signal being fed to said pulse modulator for transmission by said pulsed radar system; and phase sensitive detection means having a first input responsive to selected ones of the beat frequencies between received echoes of said transmitted signals and further having a reference input responsive to said modulating frequency for providing a phase-detected output signal.

Claim 9

A pulsed radar system including a pulse modulator and comprising a source of a modulating frequency at least as high as that represented by the reciprocal of the pulsewidth provided by said pulsed radar system; closed loop radio frequency single side band modulating means responsive to said modulating frequency for generating a side band signal representing at least two mutually coherent, concomitant and discrete frequencies, uniformly spaced apart in frequency by said modulating frequency, said side band signal being fed to said pulse modulator for transmission by said pulsed radar system; and phase sensitive detection means having a first input responsive to selected ones of the beat frequencies between received echoes of said transmitted signals and further having a reference input responsive to said modulating frequency for providing a phase-detected output signal.

Claim 10

In a radar system having enhanced small target response and including means having an input for concomitantly transmitting radio frequency energy at a plurality of mutually-coherent discrete frequencies and receiving means responsive to received echoes of said energy reflected from a target, the combination comprising generating means for generating a reference modulating frequency at least as high as the reciprocal of the pulsewidth of said pulsed energy and representing an integer submultiple of a preselected intermediate frequency; radio frequency single side band modulator mixing means having an input coupled to an output of said generating means and providing a side band signal; magic tee radio frequency signal combining means interposed at said output of said single side band modulator for combining said side band signal as a feedback signal with said output of said generating means and for extracting said side band signal for transmission purposes, said extracted signal being fed to said input of said transmitting means; and coherent intermediate frequency receiver means responsive to said modulating frequency and selected ones of the beat frequencies between said received echoes providing a receiver output signal.

Claim 11

In a radar system having enhanced small target response and including means having an input for concomitantly transmitting radio frequency energy at a plurality of mutually-coherent discrete frequencies and receiving means responsive to received echoes of said energy reflected from a target, the combination comprising generating means for generating a reference modulating frequency at least as high as the reciprocal of the pulsewidth of said pulsed energy and representing an integer submultiple of a preselected intermediate frequency; radio frequency single side band modulator mixing means having an input coupled to an output of said generating means and providing a side band signal; magic tee radio frequency signal combining means interposed at said output of said single side band modulator for combining said side band signal as a feedback signal with said output of said generating means and for extracting said side band signal for transmission purposes, said extracted signal being fed to said input of said transmitting means; and coherent intermediate frequency receiver means responsive to said modulating frequency and selected ones of the beat frequencies between said received echoes providing a receiver output signal.

Claim 12

In a pulsed radar system having enhanced small target response and including means having an input for concomitantly transmitting pulsed energy at a plurality of discrete frequencies uniformly spaced apart in frequency the combination comprising generating means for generating a reference modulating frequency at least as large as the reciprocal of the pulsewidth of said pulsed energy and representing an integer submultiple of a preselected intermediate frequency; radio frequency single side band modulator mixing means having an input coupled to an output of said generating means and providing an upper and a lower side band signal; magic-tee radio frequency signal combining means interposed at said input of said mixing means for combining one of said side band signals as a feedback signal with the output of said generating means and for extracting said side band signal for transmission purposes, said extracted signal being fed to said input of said transmitting means non-linear detection means responsive to received echoes of said transmitted frequencies for providing signals at the beat frequency differences therebetween; bandpass limited means responsively coupled to said detection means and having a center frequency equal to an integer multiple of said modulating frequency; and a phase-sensitive detector having a first and second input, each responsively coupled to the output of a exclusive one of said generating means and said bandpass limited means.

Claim 13

In a pulsed radar system having enhanced small target response and including means having an input for concomitantly transmitting pulsed energy at a plurality of discrete frequencies uniformly spaced apart in frequency the combination comprising generating means for generating a reference modulating frequency at least as large as the reciprocal of the pulsewidth of said pulsed energy and representing an integer submultiple of a preselected intermediate frequency; radio frequency single side band modulator mixing means having an input coupled to an output of said generating means and providing an upper and a lower side band signal; magic-tee radio frequency signal combining means interposed at said input of said mixing means for combining one of said side band signals as a feedback signal with the output of said generating means and for extracting said side band signal for transmission purposes, said extracted signal being fed to said input of said transmitting means non-linear detection means responsive to received echoes of said transmitted frequencies for providing signals at the beat frequency differences therebetween; bandpass limited means responsively coupled to said detection means and having a center frequency equal to an integer multiple of said modulating frequency; and a phase-sensitive detector having a first and second input, each responsively coupled to the output of a exclusive one of said generating means and said bandpass limited means.

Claim 14

In a pulsed radar system having enhanced small target response and including means having an input for concomitantly transmitting pulsed energy at a plurality of mutually-coherent frequencies uniformly spaced apart in frequency, and receiving means responsive to received echoes of said pulsed energy reflected from a target, the combination comprising a source of a spacing frequency at least as high as the reciprocal of the pulsewidth of said pulsed energy and representing a preselected intermediate frequency; radio frequency single side band modulation means coupled to said source and providing a single side band signal; bandpass limited means responsive to said side band signal for providing a feedback signal; radio frequency signal combining means interposed between said source and said modulation means for combining said feedback signal with an input of said source and for extracting said feedback signal for transmission purposes, said extracted signal being fed to said input of said transmitting means; and coherent intermediate frequency receiver means including phase sensitive detection means responsive to said spacing frequency and to selected ones of the beat frequencies between said received echoes for providing a coherently-detected receiver signal.

Claim 15

In a pulsed radar system having enhanced small target response and including means having an input for concomitantly transmitting pulsed energy at a plurality of mutually-coherent frequencies uniformly spaced apart in frequency, and receiving means responsive to received echoes of said pulsed energy reflected from a target, the combination comprising a source of a spacing frequency at least as high as the reciprocal of the pulsewidth of said pulsed energy and representing a preselected intermediate frequency; radio frequency single side band modulation means coupled to said source and providing a single side band signal; bandpass limited means responsive to said side band signal for providing a feedback signal; radio frequency signal combining means interposed between said source and said modulation means for combining said feedback signal with an input of said source and for extracting said feedback signal for transmission purposes, said extracted signal being fed to said input of said transmitting means; and coherent intermediate frequency receiver means including phase sensitive detection means responsive to said spacing frequency and to selected ones of the beat frequencies between said received echoes for providing a coherently-detected receiver signal.

Claim 16

In a moving target indicating system for a platform moving relative to a clutter patch, means for enhancing the response of said system to a target moving relative to both said clutter patch and said platform, and having enhanced small target response and including means having a spacing frequency input for concomitantly transmitting pulsed energy at a plurality of mutually coherent frequency uniformly spaced apart in frequency and receiving means responsive to received echoes of said pulsed energy reflected from a target, the combination comprising a source of a spacing frequency at least as high as the reciprocal of the pulsewidth of said pulsed energy and representing a preselected intermediate frequency; single side band modulation means coupled to said source and providing a single side band signal; bandpass limited means responsive to said side band signal for providing a feedback signal; signal combining means interposed at said input of said single side band modulation means for combining said feedback signal with the output of said source and for extracting said feedback signal for energy transmission purposes, said transmitting means having an input responsive to said extracted signal; coherent intermediate frequency receiver means including phase sensitive detection means responsive to said spacing frequency and to the beat frequencies between said received echoes for providing a coherently detected receiver signal, and doppler processing means responsive to said coherently detected receiver signal for providing an output indicative of said detected target.

Claim 17

In a moving target indicating system for a platform moving relative to a clutter patch, means for enhancing the response of said system to a target moving relative to both said clutter patch and said platform, and having enhanced small target response and including means having a spacing frequency input for concomitantly transmitting pulsed energy at a plurality of mutually coherent frequency uniformly spaced apart in frequency and receiving means responsive to received echoes of said pulsed energy reflected from a target, the combination comprising a source of a spacing frequency at least as high as the reciprocal of the pulsewidth of said pulsed energy and representing a preselected intermediate frequency; single side band modulation means coupled to said source and providing a single side band signal; bandpass limited means responsive to said side band signal for providing a feedback signal; signal combining means interposed at said input of said single side band modulation means for combining said feedback signal with the output of said source and for extracting said feedback signal for energy transmission purposes, said transmitting means having an input responsive to said extracted signal; coherent intermediate frequency receiver means including phase sensitive detection means responsive to said spacing frequency and to the beat frequencies between said received echoes for providing a coherently detected receiver signal, and doppler processing means responsive to said coherently detected receiver signal for providing an output indicative of said detected target.