Antijam communications system

Claim 2

An antijam, two-way communications station comprising a radiant energy transmitter and receiver, a signal source connected to said transmitter, a signal subtractor having one input connected to said signal source, another input connected to said receiver and an output, means for selectively connecting said transmitter to said receiver and the output of said signal source for establishing a degenerative feedback loop for noise-free transmission and reception with another station of substantially the same type.

Claim 3

An antijam communications system for transmitting a signal in the presence of noise that may be larger than said signal comprising a signal source, a first transmitter connected to said signal source and a first receiver at a first location, a second transmitter and a second receiver at a second location, a first communications channel connected between said first transmitter and second receiver, a second communications channel connected between said second transmitter and first receiver, means for connecting said second receiver to said second transmitter and also including a signal output, a filter connected to said first receiver for eliminating frequencies above and below the frequencies of the signal that may cause regeneration, a phase delay control circuit connected to said filter for delaying the signal from said filter by an amount such that the delay time around said system will be equal to a 180° phase shift of said signal, a signal adder connected to said signal source and said phase delay control circuit for adding the 180° phase shifted signal to said signal to provide an output connected to said first transmitter which has only the noise generated within said system shifted by 180° of said signal whereby the effect of the noise in said system on the audio output in said system may be effectively reduced.

Claim 4

An antijam communications system for transmitting a signal in the presence of noise that may be larger than said signal comprising a signal source, a first transmitter connected to said signal source and a first receiver at a first location, a second transmitter and a second receiver at a second location, a first communications channel connected between said first transmitter and second receiver, a second communications channel connected between said second transmitter and first receiver, means for connecting said second receiver to said second transmitter and also including a signal output, a filter connected to said first receiver for eliminating frequencies above and below the frequencies of the signal that may cause regeneration, a phase delay control circuit connected to said filter for delaying the signal from said filter by an amount such that the delay time around said system will be equal to a 180° phase shift of said signal, a signal adder connected to said signal source and said phase delay control circuit for adding the 180° phase shifted signal to said signal to provide an output connected to said first transmitter which has only the noise generated within said system shifted by 180° of said signal whereby the effect of the noise in said system on the audio output in said system may be effectively reduced.

Claim 5

An antijam communication method for transmitting and receiving a desired signal which is subjected to superimposed noise in a communication channel, comprising the steps of: generating the desired signal at a communication station; transmitting said desired signal from said communication station to a transmitting station; transmitting said desired signal from said transmitting station to a receiving station through said communication channel; receiving said desired signal and said superimposed noise at said receiving station; transmitting said desired signal and said superimposed noise from said receiving station to said communication station; receiving said desired signal and said superimposed noise at said communication channel; subtracting said received desired signal and superimposed noise from the desired signal being generated at said communication station so that said desired signals cancel each other and leave an inverted noise signal; and transmitting said inverted noise signal to said transmitting station with said desired signal which is generated at said communication station.

Claim 6

An antijam communication method for transmitting and receiving a desired signal which is subjected to superimposed noise in a communication channel, comprising the steps of: generating the desired signal at a communication station; transmitting said desired signal from said communication station to a transmitting station; transmitting said desired signal from said transmitting station to a receiving station through said communication channel; receiving said desired signal and said superimposed noise at said receiving station; transmitting said desired signal and said superimposed noise from said receiving station to said communication station; receiving said desired signal and said superimposed noise at said communication channel; subtracting said received desired signal and superimposed noise from the desired signal being generated at said communication station so that said desired signals cancel each other and leave an inverted noise signal; and transmitting said inverted noise signal to said transmitting station with said desired signal which is generated at said communication station.

Claim 7

Apparatus for reducing noise in a signal communication system without a corresponding reduction in signal strength, comprising: a signal-carrying channel; a source of essentially noise free signals coupled to said channel; amplification means located in said channel, by which means undesired noise components are introduced into said channel; feedback means for said system, said feedback means comprising: signal adder means having an output and two input paths; phase shift means having an input coupled to said channel at a point containing the undesired noise components and an output coupled to one input of said signal adder means, whereby the entire signal and the undesired noise components fed to said adder means are essentially inverted; means coupling said source of signals to the other input of said adder means, whereby upon algebraic addition of the signals from said source and the inverted signals containing noise components, there is produced at the output of said adder means inverted noise signals only; and means coupling the output of said adder means to a point in said channel at which noise components are essentially absent, whereby the inverted noise components are fed via said channel to cancel the undesirable noise components introduced in said channel.

Claim 8

Apparatus for reducing noise in a signal communication system without a corresponding reduction in signal strength, comprising: a signal-carrying channel; a source of essentially noise free signals coupled to said channel; amplification means located in said channel, by which means undesired noise components are introduced into said channel; feedback means for said system, said feedback means comprising: signal adder means having an output and two input paths; phase shift means having an input coupled to said channel at a point containing the undesired noise components and an output coupled to one input of said signal adder means, whereby the entire signal and the undesired noise components fed to said adder means are essentially inverted; means coupling said source of signals to the other input of said adder means, whereby upon algebraic addition of the signals from said source and the inverted signals containing noise components, there is produced at the output of said adder means inverted noise signals only; and means coupling the output of said adder means to a point in said channel at which noise components are essentially absent, whereby the inverted noise components are fed via said channel to cancel the undesirable noise components introduced in said channel.

Claim 9

Apparatus according to claim 4 wherein said feedback means includes filter means for excluding frequencies not within a band composing the signals from said source.