Spectrum differential noise squelch system

Claim 2

A noise squelch system for use in a receiver of the type having a discriminator for detecting intelligence signals coupled to the output of a bandpass filter having upper and lower frequency 6 db points defining a frequency bandwidth comprising: first means coupled to said discriminator output for sensing the noise level over a first band of baseband frequencies centered at a frequency lower than the value of said frequency bandwidth and second means coupled to said discriminator output for sensing the noise level over a second separate band of baseband frequencies centered at a frequency higher than the value of said frequency bandwidth, and means including comparator means coupled between said first and second sensing means at the output of said discriminator for squelching the output signal from the discriminator when the difference in the noise levels over said first and second bands of baseband frequencies is below a given value, and for passing the output signal from the discriminator when said difference is above said given value.

Claim 3

The combination claimed in claim 1 wherein said first band of baseband frequencies is a narrow band compared to the bandwidth of said bandpass filter and is centered at a frequency approximately 0.65 times the value of said frequency bandwidth of said bandpass filter.

Claim 4

The combination claimed in claim 1 wherein said second band of frequencies is a narrow band of frequencies compared to the bandwidth of said bandpass filter and includes a frequency approximately 1.2 times the value of said frequency bandwidth of said bandpass filter.

Claim 5

The combination claimed in Claim 1 wherein said second band of frequencies is centered at a frequency approximately 1.2 times the value of said frequency bandwidth of said bandpass filter.

Claim 6

In a receiver of the type having a discriminator coupled to the output of a bandpass filter for detecting intelligence signals and a means for coupling the intelligence signals at the output of the discriminator to a utilization device for said intelligence signals, said bandpass filter having upper and lower frequency 6 db points defining a frequency bandwidth, a noise squelch system comprising: control means coupled between said discriminator and said utilization device for disrupting the coupling of said intelligence signals and noise to said utilization device; a comparator coupled to said control means; means coupled between the output of said discriminator and said comparator for coupling noise signals at baseband frequencies above the intelligence signals and at frequencies centered at about 0.65 times the value of said frequency bandwidth of said bandpass filter to said comparator; means coupled between the output of said discriminator and said comparator for coupling noise signals at baseband frequencies centered at about 1.2 times the value of said frequency bandwidth of said bandpass filter to said comparator, and said comparator being responsive to a given value of difference in the noise level at frequencies centered at 0.65 times the value of said frequency bandwidth of said bandpass filter relative to the noise level at frequencies centered at 1.2 times the value of said frequency bandwidth of said bandpass filter for operating said control means to determine the coupling of said intelligence signals to said utilization device.

Claim 7

In a receiver of the type having a discriminator coupled to the output of a bandpass filter for detecting intelligence signals and a means for coupling the intelligence signals at the output of the discriminator to a utilization device for said intelligence signals, said bandpass filter having upper and lower frequency 6 db points defining a frequency bandwidth, a noise squelch system comprising: control means coupled between said discriminator and said utilization device for disrupting the coupling of said intelligence signals and noise to said utilization device; a comparator coupled to said control means; means coupled between the output of said discriminator and said comparator for coupling noise signals at baseband frequencies above the intelligence signals and at frequencies centered at about 0.65 times the value of said frequency bandwidth of said bandpass filter to said comparator; means coupled between the output of said discriminator and said comparator for coupling noise signals at baseband frequencies centered at about 1.2 times the value of said frequency bandwidth of said bandpass filter to said comparator, and said comparator being responsive to a given value of difference in the noise level at frequencies centered at 0.65 times the value of said frequency bandwidth of said bandpass filter relative to the noise level at frequencies centered at 1.2 times the value of said frequency bandwidth of said bandpass filter for operating said control means to determine the coupling of said intelligence signals to said utilization device.