Interference suppression in a receiver by envelope variation modulation

Claim 2

In a radio receiver, a nonlinear processing circuit for suppressing a strong interfering signal in favor of a desired signal which comprises, means for deriving from a composite received signal consisting of the sum of said desired signal and said stronger interfering signal a control signal which represents the instantaneous projection of said desired signal vector on said interfering signal vector and is a function of the phase difference between said interfering signal and said desired signal, and means for multiplying said control signal and said composite received signal to produce said desired signal with said interfering signal substantially suppressed.

Claim 3

A nonlinear processing circuit in accordance with claim 1 wherein said means for deriving a control signal from said composite received signal comprises an envelope detector, means for applying said composite received signal to the input of said envelope detector, and circuit means including a resistive component having a value R and a capacitive component having a value C for processing the output signal Env (r(t) ) produced by said envelope detector, said circuit means having a transfer function expressible as

Claim 4

A nonlinear processing circuit in accordance with claim 1 wherein said circuit means for processing the output of said envelope detector comprises an averager having an input coupled to the output of said envelope detector, and a difference amplifier having a first input coupled to the output of said envelope detector and a second input coupled to the output of said averager, said control signal being available at the output of said difference amplifier.

Claim 5

In a radio receiver, a nonlinear processor comprising, in combination, an envelope detector, circuit means including a resistive component having a value R and a capacitive component having a value C for processing the output signal Env (r(t)) of said envelope detector, said circuit means having a transfer function expressible as multiplier having first and second inputs and an output, means coupling the output of said circuit means to the first input of said multiplier, and means for applying said received signal to the second input of said multiplier, the output of said multiplier being the output of said nonlinear processor.

Claim 6

In a radio receiver, a nonlinear processor comprising, in combination, an envelope detector, circuit means including a resistive component having a value R and a capacitive component having a value C for processing the output signal Env (r(t)) of said envelope detector, said circuit means having a transfer function expressible as multiplier having first and second inputs and an output, means coupling the output of said circuit means to the first input of said multiplier, and means for applying said received signal to the second input of said multiplier, the output of said multiplier being the output of said nonlinear processor.

Claim 7

A nonlinear processor in accordance with claim 4 wherein said circuit means for processing the output of said envelope detector comprises an averager having an input coupled to the output of said envelope detector, and a difference amplifier having a first input coupled to the output of said enVelope detector and a second input coupled to the output of said averager, the output of said difference amplifier being the output of said circuit means.

Claim 8

A nonlinear processor in accordance with claim 4 wherein said means coupling the output of said circuit means to the first input of said multiplier includes a limiter for quantizing the signal produced at the output of said circuit means into a binary signal.

Claim 9

A nonlinear processor in accordance with claim 4 wherein said received signal includes a desired spread spectrum signal, and said receiver further includes a correlator for recovering narrow band information from said spread spectrum signal, the input of said correlator being coupled to the output of said multiplier.

Claim 10

A nonlinear processor in accordance with claim 7 wherein said spread spectrum signal is quaternary phased.

Claim 11

In a radio communication system including a transmitter and receiver, means for suppressing a strong interfering signal in said receiver in favor of the desired signal transmitted by said transmitter which comprises, modulation means in said transmitter for producing a spread spectrum signal, a correlator in said receiver for recovering narrow band information from said spread spectrum signal, and a nonlinear processing circuit connected ahead of said correlator in said receiver and comprising means for deriving from a composite received signal consisting of the sum of said desired spread spectrum signal and said stronger interfering signal a control signal which represents the instantaneous projection of said desired spread spectrum signal vector on said interfering signal vector, and means for multiplying said control signal and said composite received signal to produce said desired spread spectrum signal with said interfering signal substantially suppressed, the output of said multiplying means being coupled to the input of said correlator.

Claim 12

In a radio communication system including a transmitter and receiver, means for suppressing a strong interfering signal in said receiver in favor of the desired signal transmitted by said transmitter which comprises, modulation means in said transmitter for producing a spread spectrum signal, a correlator in said receiver for recovering narrow band information from said spread spectrum signal, and a nonlinear processing circuit connected ahead of said correlator in said receiver and comprising means for deriving from a composite received signal consisting of the sum of said desired spread spectrum signal and said stronger interfering signal a control signal which represents the instantaneous projection of said desired spread spectrum signal vector on said interfering signal vector, and means for multiplying said control signal and said composite received signal to produce said desired spread spectrum signal with said interfering signal substantially suppressed, the output of said multiplying means being coupled to the input of said correlator.

Claim 13

A communication system according to claim 9 wherein said means for deriving a control signal from said composite received signal comprises an envelope detector, means for applying said composite received signal to the input of said envelope detector, and circuit means including a resistive component having a value R and a capacitive component having a value C for processing the output signal Env (r(t) produced by said envelope detector, said circuit means having a transfer function expressible as

Claim 14

A communication system according to claim 10 wherein said circuit means for processing the output of said envelope detector comprises an averager having an input coupled to the output of said envelope detector, and a difference amplifier having a first input coupled to the output of said envelope detector and a second input coupled to the output of said averager, said control signal being available at the output of said difference amplifier.

Claim 15

A communication system according to claim 11 wherein said modulation means in the transmitter includes a four-phase modulator and is operative to produce a quaternary-phased spread spectrum signal.