Noise suppression arrangement for communication receivers

Claim 2

In a superheterodyne receiver for minimizing the effects of atmospheric impulsive noise on binary signals being received, the combination of a radio frequency amplifying circuit; an intermediate frequency amplifying circuit connected thereto; signal clipping means connected to the output of said intermediate frequency circuit and operating to produce a first signal consisting of those peak portions of the amplified intermediate frequency signal whose amplitude exceeds a predetermined threshold level and a second signal consisting of those portions of the intermediate frequency signal whose amplitude is below said threshold level; means responsive to said first signal for adjusting the gain of said radio frequency amplifying circuit or the gain of said intermediate frequency amplifying circuit such that said signal clipping means produces a second signal during a predetermined percentage of the intermediate frequency signal time; a narrow band filter; and means for feeding said second signal to the input of said narrow band filter so as to develop an output signal in its output circuit.

Claim 3

In a superheterodyne communication receiver for minimizing the effects of atmospheric impulsive noise on the reception of binary signals, the combination of a radio frequency amplifying circuit; an intermediate frequency amplifying circuit connected thereto; a limiting circuit connected to said intermediate frequency amplifying circuit for clipping the amplified intermediate frequency signals to a preset amplitude level; means responsive to the peak portions of the intermediate frequency signals which exceed said preset level for adjusting said preset level so that clipping of said intermediate frequency signals occur during a predetermined percentage of intermediate frequenCy signal time; a narrow band filter; and means for feeding the intermediate frequency signals that have been clipped to the input of said narrow band filter, thereby to develop output signals in its output circuit.

Claim 4

In a superheterodyne communication receiver for minimizing the effects of atmospheric impulsive noise on the reception of binary signals, the combination of a radio frequency amplifying circuit; an intermediate frequency amplifying circuit connected thereto; a limiting circuit connected to said intermediate frequency amplifying circuit for clipping the amplified intermediate frequency signals to a preset amplitude level; means responsive to the peak portions of the intermediate frequency signals which exceed said preset level for adjusting said preset level so that clipping of said intermediate frequency signals occur during a predetermined percentage of intermediate frequenCy signal time; a narrow band filter; and means for feeding the intermediate frequency signals that have been clipped to the input of said narrow band filter, thereby to develop output signals in its output circuit.

Claim 5

A noise suppression arrangement for use in a superheterodyne communication receiver of the type having a radio frequency amplifying circuit and an intermediate frequency amplifying circuit connected thereto, comprising signal clipping means connected to the output of said intermediate frequency circuit and operating to produce a first signal consisting of those portions of the amplified intermediate frequency signal whose amplitude exceeds a threshold level and a second signal consisting of those portions of the intermediate frequency signal whose amplitude is below said threshold level; means for amplifying said first signal; means for clipping and detecting said amplified first signal; means for integrating said detected signal so as to develop a control signal; means for comparing the amplitude of said control signal with a reference voltage representing a predetermined percentage of intermediate frequency signal clipping time and for producing a difference voltage indicative of the inequality thereof; means responsive to said difference voltage for controlling the relative levels of the intermediate frequency signal and said threshold level so that said signal clipping means operates during said predetermined percentage of intermediate frequency signal time; and a narrow band filter connected to said signal clipping means for developing an output signal from said second signal.

Claim 6

A noise suppression arrangement for use in a superheterodyne communication receiver of the type having a radio frequency amplifying circuit and an intermediate frequency amplifying circuit connected thereto, comprising signal clipping means connected to the output of said intermediate frequency circuit and operating to produce a first signal consisting of those portions of the amplified intermediate frequency signal whose amplitude exceeds a threshold level and a second signal consisting of those portions of the intermediate frequency signal whose amplitude is below said threshold level; means for amplifying said first signal; means for clipping and detecting said amplified first signal; means for integrating said detected signal so as to develop a control signal; means for comparing the amplitude of said control signal with a reference voltage representing a predetermined percentage of intermediate frequency signal clipping time and for producing a difference voltage indicative of the inequality thereof; means responsive to said difference voltage for controlling the relative levels of the intermediate frequency signal and said threshold level so that said signal clipping means operates during said predetermined percentage of intermediate frequency signal time; and a narrow band filter connected to said signal clipping means for developing an output signal from said second signal.

Claim 7

In an arrangement as defined in claim 3 wherein said means responsive to the difference voltage for controlling the relative levels of the IF signal and said threshold level regulates the gain of said radio frequency amplifying circuit or said intermediate frequency amplifying circuit.

Claim 8

In an arrangement as defined in claim 3 wherein said means responsive to the difference voltage for controlling the relative levels of the IF signal and said threshold level regulates said threshold level.