Signal cancellation

Claim 3

The system of claim 1 wherein said combining means comprises: means for selecting the two phase signals closest in phase to said unwanted signal; means for combining said two phase signals in variable proportions to form a cancellation signal; means for comparing the phase of said unwanted signal and said phase signals; means responsive to the phase difference between said unwanted signal and said phase signals for varying the proportions of said phase signals so that the phase of said cancellation signal is substantially 180* out of phase with said unwanted signal; and means responsive to the remainder of said unwanted signal to adjust the ampLitude of said cancellation signal so that it substantially equal to that of said unwanted signal.

Claim 4

The system of claim 1 wherein said phase signals comprise four signals approximately 90* apart and the phase quadrant into which said unwanted signal falls is detected, said phase guadrant being used to select the two phase signals to be combined to form said cancellation signal.

Claim 5

The system of claim 1 wherein said electrical circuitry comprises seismic amplifiers and said unwanted signal comprises stray power line frequencies.

Claim 6

The system of claim 1 wherein said plurality of phase signals and said reference signal are converted to square-wave signals having the same phase as the phase and reference signals and the means for detecting the phase of the unwanted signal comprises a phase comparing circuit, said square-wave signals being coupled to said phase comparing circuit; the signal from said phase comparing circuit being used to control the means used for combining the phase signals to produce a cancellation signal.

Claim 7

A cancellation system for cancelling stray power line signals in a seismic amplifying system, said cancellation system comprising; detecting means disposed to produce a source signal related to the phase and amplitude of the stray power line signal; phase generating means for generating a plurality of phase signals from said source signal, each of said source signals being displaced in phase from the adjacent phase signals by equal phase angles; a second detecting means coupled to said seismic amplifying system for detecting the unwanted signal; first squaring means coupled to said generating means for squaring said phase signals; second squaring means coupled to said second detecting means for squaring said unwanted signal; phase comparing means, said first and second squaring means being coupled to said phase comparing means; mixing means, switch means, said switch means being coupled to said phase comparing circuit and said generating means, said switch means being closed in response to the signal from said phase comparing means to transmit portions of at least two of said phase signals to said mixing means whereby said mixing means produce a signal 180* out of phase with said unwanted signal.

Claim 8

A cancellation system for cancelling stray power line signals in a seismic amplifying system, said cancellation system comprising; detecting means disposed to produce a source signal related to the phase and amplitude of the stray power line signal; phase generating means for generating a plurality of phase signals from said source signal, each of said source signals being displaced in phase from the adjacent phase signals by equal phase angles; a second detecting means coupled to said seismic amplifying system for detecting the unwanted signal; first squaring means coupled to said generating means for squaring said phase signals; second squaring means coupled to said second detecting means for squaring said unwanted signal; phase comparing means, said first and second squaring means being coupled to said phase comparing means; mixing means, switch means, said switch means being coupled to said phase comparing circuit and said generating means, said switch means being closed in response to the signal from said phase comparing means to transmit portions of at least two of said phase signals to said mixing means whereby said mixing means produce a signal 180* out of phase with said unwanted signal.

Claim 9

The cancellation system of claim 6 wherein said generating means produces four phase signals having substantially 90* phase angles between adjacent phases.

Claim 10

The cancellation system of claim 7 wherein said switch means comprise a pair of semi-conductor devices, two adjacent phase signals being coupled to said semi-conductor devices, said semi-conductor devices being responsive to the signal from said phase comparing circuit to conduct to transmit portions of said two adjacent phase signals to said mixing circuit.