Phase-locked tracking filter

Claim 2

A phase-locked tracking filter comprising: a. a band-pass filter including at least one resistor and one capacitor such that on change of the value of one of the resistor and capacitor, there is a change of central frequency of operation of the overall filter for maximum noise rejection relative to the desired input signal to the filter, b. a 90* phase shifter connected to the output of the band-pass filter, c. a phase-sensitive detector for comparing the output voltage from the phase-shifter and a voltage signal from the input of the filter and providing a control signal related to the phase difference between the input and output voltages of the filter, d. an integrator and amplifier for smoothing and amplifying said control signal, and e. a tuning control means connected to said integrator and amplifier for varying the value of one of said resistor and capacitor on change of value of the control signal.

Claim 3

A phase-locked tracking filter as in claim 1 wherein the tuning control means is a dual photo-sensitive resistor.

Claim 4

A phase-locked tracking filter comprising: a. a band-pass filter including at least one electrical element such that on change of the electrical value of said element there is a change of central frequency of operation of the overall filter for maximum noise rejection relative to a desired input signal to the filter, b. a first Schmitt trigger connected to the filter output, c. a second Schmitt trigger connected to the filter input, one of said Schmitt triggers being an inverting type and the other a non-inverting type for providing square voltages of the same phase as said input or output filter voltages, d. a monostable multivibrator for producing a narrow control pulse connected to one of said Schmitt triggers, e. a phase-sensitive detector for accepting signals from the monostable multivibrator and the other Schmitt trigger and providing a square wave control signal output whose mean DC value is related to the phase difference between input and output filter voltages, f. integrator and amplifier means for smoothing and amplifying the output of said detector, and g. tuning control means connected to said integrator and amplifier for varying the value of the said element on change of value of said control signal.

Claim 5

A phase-locked tracking filter comprising: a. a band-pass filter including at least one electrical element such that on change of the electrical value of said element there is a change of central frequency of operation of the overall filter for maximum noise rejection relative to a desired input signal to the filter, b. a first Schmitt trigger connected to the filter output, c. a second Schmitt trigger connected to the filter input, one of said Schmitt triggers being an inverting type and the other a non-inverting type for providing square voltages of the same phase as said input or output filter voltages, d. a monostable multivibrator for producing a narrow control pulse connected to one of said Schmitt triggers, e. a phase-sensitive detector for accepting signals from the monostable multivibrator and the other Schmitt trigger and providing a square wave control signal output whose mean DC value is related to the phase difference between input and output filter voltages, f. integrator and amplifier means for smoothing and amplifying the output of said detector, and g. tuning control means connected to said integrator and amplifier for varying the value of the said element on change of value of said control signal.

Claim 6

A phase-locked tracking filter as in claim 3 wherein the tuning control means is a dual photo-sensitive resistor.

Claim 7

A phase-locked tracking filter as in claim 3 wherein the tuning control means is a field effect transistor.

Claim 8

A phase-locked tracking filter as in claim 3 wherein the electrical element is a resistor.

Claim 9

A phase-locked tracking filter as in claim 3 wherein the electrical element is a capacitor.

Claim 10

A phase-locked tracking filter as in claim 3 wherein the electrical element is a solid-state current cOntrol device.

Claim 11

A phase-locked tracking filter comprising: a. a band-pass filter including a resistor such that on change of electrical value of the resistor there is a change of central frequency of operation of said band-pass filter, b. a non-inverting Schmitt trigger connected to the input of said filter to provide a square wave voltage in phase with the filter input signal, c. an inverting Schmitt trigger connected to the output of said filter to provide a square wave 180* out of phase with the filter output, d. a monostable multivibrator connected to the output of the inverting Schmitt trigger to provide a narrow negative pulse at the negative edge of the square wave from the trigger, e. a flip-flop phase-sensitive detector for accepting the narrow negative pulses and the output from the non-inverting Schmitt trigger and providing a square wave voltage whose mean DC value is related to the phase difference between filter input and output voltages, f. means for integrating and amplifying said square wave voltage, and g. tuning control means connected to the integrating and amplifying means for varying the electrical value of said resistor.

Claim 12

A phase-locked tracking filter comprising: a. a band-pass filter including a resistor such that on change of electrical value of the resistor there is a change of central frequency of operation of said band-pass filter, b. a non-inverting Schmitt trigger connected to the input of said filter to provide a square wave voltage in phase with the filter input signal, c. an inverting Schmitt trigger connected to the output of said filter to provide a square wave 180* out of phase with the filter output, d. a monostable multivibrator connected to the output of the inverting Schmitt trigger to provide a narrow negative pulse at the negative edge of the square wave from the trigger, e. a flip-flop phase-sensitive detector for accepting the narrow negative pulses and the output from the non-inverting Schmitt trigger and providing a square wave voltage whose mean DC value is related to the phase difference between filter input and output voltages, f. means for integrating and amplifying said square wave voltage, and g. tuning control means connected to the integrating and amplifying means for varying the electrical value of said resistor.

Claim 13

A phase-locked tracking filter comprising: a. a band-pass filter including a capacitor such that on change of electrical value of the capacitor there is a change of central frequency of operation of said band-pass filter, b. a non-inverting Schmitt trigger connected to the input of said filter to provide a square wave voltage in phase with the filter input signal, c. an inverting Schmitt trigger connected to the output of said filter to provide a square wave 180* out of phase with the filter output, d. a monostable multivibrator connected to the output of the inverting Schmitt trigger to provide a narrow negative pulse at the negative edge of the square wave from the trigger, e. a flip-flop phase-sensitive detector for accepting the narrow negative pulses and the output from the non-inverting Schmitt trigger and providing a square wave voltage whose mean DC value is related to the phase difference between filter input and output voltages, f. means for integrating and amplifying said square wave voltage, and g. tuning control means connected to the integrating and amplifying means for varying the electrical value of said capacitor.

Claim 14

A phase-locked tracking filter comprising: a. a band-pass filter including a capacitor such that on change of electrical value of the capacitor there is a change of central frequency of operation of said band-pass filter, b. a non-inverting Schmitt trigger connected to the input of said filter to provide a square wave voltage in phase with the filter input signal, c. an inverting Schmitt trigger connected to the output of said filter to provide a square wave 180* out of phase with the filter output, d. a monostable multivibrator connected to the output of the inverting Schmitt trigger to provide a narrow negative pulse at the negative edge of the square wave from the trigger, e. a flip-flop phase-sensitive detector for accepting the narrow negative pulses and the output from the non-inverting Schmitt trigger and providing a square wave voltage whose mean DC value is related to the phase difference between filter input and output voltages, f. means for integrating and amplifying said square wave voltage, and g. tuning control means connected to the integrating and amplifying means for varying the electrical value of said capacitor.

Claim 15

A phase-locked tracking filter comprising: a. a band-pass filter including a field effect transistor such that on change of electrical value of the transistor there is a change of central frequency of operation of said band-pass filter, b. a non-inverting Schmitt trigger connected to the input of said filter to provide a square wave voltage in phase with the filter input signal, c. an inverting Schmitt trigger connected to the output of said filter to provide a square wave 180* out of phase with the filter output, d. a monostable multivibrator connected to the output of the inverting Schmitt trigger to provide a narrow negative pulse at the negative edge of the square wave from the trigger, e. a flip-flop phase-sensitive detector for accepting the narrow negative pulses and the output from the non-inverting Schmitt trigger and providing a square wave voltage whose mean DC value is related to the phase difference between filter input and output voltages, f. means for integrating and amplifying said square wave voltage, and g. tuning control means connected to the integrating and amplifying means for varying the electrical value of said transistor.

Claim 16

A phase-locked tracking filter comprising: a. a band-pass filter including a field effect transistor such that on change of electrical value of the transistor there is a change of central frequency of operation of said band-pass filter, b. a non-inverting Schmitt trigger connected to the input of said filter to provide a square wave voltage in phase with the filter input signal, c. an inverting Schmitt trigger connected to the output of said filter to provide a square wave 180* out of phase with the filter output, d. a monostable multivibrator connected to the output of the inverting Schmitt trigger to provide a narrow negative pulse at the negative edge of the square wave from the trigger, e. a flip-flop phase-sensitive detector for accepting the narrow negative pulses and the output from the non-inverting Schmitt trigger and providing a square wave voltage whose mean DC value is related to the phase difference between filter input and output voltages, f. means for integrating and amplifying said square wave voltage, and g. tuning control means connected to the integrating and amplifying means for varying the electrical value of said transistor.