Distortion compensator for phase modulation systems

Claim 2

A phase modulation communication system with distortion compensation, comprising signal transmitting means; said signal transmitting means comprising a source of rf carrier signal, a phase modulator, a modulating signal, said phase modulator receiving said rf carrier signal and said modulating signal as inputs thereto and providing a phase modulated carrier output signal for transmission; signal receiving means, said signal receiving means comprising a receiver phase detector receiving said phase modulated carrier signal as a first input thereto, means for generating a carrier signal phase locked 90 degrees with respect to said received carrier signal and applying said generated carrier signal as a second input to said receiver phase detector, the output of said receiver phase detector comprising a selectively filterable signal component which is a function of said modulating signal; means for distortion compensation in said communications system comprising means at said transmitter for generating a modulation feedback signal in response to the output of said transmitter phase modulator, said means for generating comprising a further phase detector with characteristics like that of said receiver phase detector receiving the output from said phase modulator and said rf carrier signal shifted 90 degrees in phase as respective inputs thereto and developing an output comprising said modulation feedback signal, a source of modulation intelligence signal, signal combining means receiving said modulation intelligence signal and said modulation feedback signal as respective inputs thereto, negative gain signal amplifying means receiving the output of said signal combining means and developing an output signal comprising said modulating signal.

Claim 3

A distortion compensated phase modulation communication system as defined in claim 1 wherein said negative gain amplifier has a gain of -A, where A is substantially greater than the unity.

Claim 4

A distortion compensated phase modulation communication system as defined in claim 2 wherein said signal combining means comprises first and second serially interconnected resistors the free ends of which receive the respective modulation intelligence signal and modulation feedback signal inputs and the junction between which comprises the output from said signal combining means.

Claim 5

A phase modulation communication system with distortion compensation comprising signal transmitting means; said signal transmitting means comprising a source of rf carrier signal, a phase modulator, a modulating signal, said phase modulator receiving said rf carrier signal and said modulating signal as respective inputs thereto and providing a phase modulated carrier output signal for transmission; signal receiving means, said signal receiving means comprising a receiver phase detector receiving said phase modulated carrier signal as a first input thereto, means for generating a carrier signal phase locked 90 degrees with respect to said received carrier signal and applying said generated carrier signal as a second input to said receiver phase detector, the output of said receiver phase detector comprising a selectively filterable signal component which is a function of said modulating signal; means for distortion compensation in said communication system comprising means at said receiver, including a further phase modulator with characteristics like that of said transmitter phase modulator receiving said generated carrier signal as a first input thereto, signal combining means, means applying said output of said receiver phase detector as a first input to said signal combining means, the output from said signal combining means applied to a negative gain amplifying means, the output of said negative gain amplifying means comprising a second input to said further phase modulator, said generated carrier signal and the output from said further Phase modulator being applied to a means for phase detecting, signal translating means receiving the output from said means for phase detecting and applying a second input to said signal combining means, and the output from said negative gain amplifying means comprising the modulation component of said received phase modulated carrier signal as a linear function of said modulating signal.

Claim 6

A phase modulation communication system with distortion compensation comprising signal transmitting means; said signal transmitting means comprising a source of rf carrier signal, a phase modulator, a modulating signal, said phase modulator receiving said rf carrier signal and said modulating signal as respective inputs thereto and providing a phase modulated carrier output signal for transmission; signal receiving means, said signal receiving means comprising a receiver phase detector receiving said phase modulated carrier signal as a first input thereto, means for generating a carrier signal phase locked 90 degrees with respect to said received carrier signal and applying said generated carrier signal as a second input to said receiver phase detector, the output of said receiver phase detector comprising a selectively filterable signal component which is a function of said modulating signal; means for distortion compensation in said communication system comprising means at said receiver, including a further phase modulator with characteristics like that of said transmitter phase modulator receiving said generated carrier signal as a first input thereto, signal combining means, means applying said output of said receiver phase detector as a first input to said signal combining means, the output from said signal combining means applied to a negative gain amplifying means, the output of said negative gain amplifying means comprising a second input to said further phase modulator, said generated carrier signal and the output from said further Phase modulator being applied to a means for phase detecting, signal translating means receiving the output from said means for phase detecting and applying a second input to said signal combining means, and the output from said negative gain amplifying means comprising the modulation component of said received phase modulated carrier signal as a linear function of said modulating signal.

Claim 7

A phase modulation communication system with distortion compensation as defined in claim 4 wherein said means for generating said receiver generated carrier signal comprises a phase locked loop, said phase locked loop comprising a loop filter to which the output from said receiver phase detector is applied, the output from said loop filter being applied to a voltage controlled oscillator, and the output of said voltage controlled oscillator comprising said generated carrier signal.

Claim 8

A distortion compensated phase modulation communication system as defined in claim 4 wherein said signal translating means translates the signal input thereto with a predetermined gain factor, the output signal from said negative gain amplifying means being defined as a constant times the arcsine of the product of a further constant times the output of said receiver phase detector, said last named constant being established as a value of unity in response to said predetermined gain factor.

Claim 9

A distortion compensated phase modulation communication system as defined in claim 4 wherein said negative gain amplifer has a gain of -A, where A is substantially greater than unity.

Claim 10

A distortion compensated phase modulation communication system as defined in claim 4 wherein said signal combining means comprises first and second serially interconnected resistors the free ends of which respectively receive the output of said receiver phase detector and the output from said means for phase detecting, and the junction between which comprises the output from said signal combining means.