Apparatus for monitoring the response of a resonant circuit

Claim 2

Apparatus for determining the response of a resonant circuit to frequency-modulated signals comprising: first circuit means for providing frequency modulated signals; resonant circuit means, exhibiting a frequency band-pass characteristic including at least a portion of said frequencymodulated signals, coupled to receive said frequency-modulated signals for translation thereof; second circuit means coupled to said resonant circuit means for determining when the amplitude of the frequency-modulated signals translated by said resonant circuit means is above a preset level greater than zero and generating a test signal having a time duration corresponding to the time period the signal translated by said resonant circuit means exceeds said preset level, and third circuit means coupled to said second circuit means for measuring the duration of said test signal to provide an indication of the response of said resonant circuit means to said frequency-modulated signals.

Claim 3

Apparatus as defined in claim 1 wherein said first circuit means includes: variable-frequency oscillator means for generating a cyclic output signal, and control circuit means coupled to said oscillator means for varying the frequency of said output signal to traverse the band-pass of said resonant circuit means.

Claim 4

Apparatus as defined in claim 2 wherein: said control circuit means controls said oscillator means so that the frequency of said output signal is varied to periodically traverse the band-pass of said resonant circuit means; said second circuit means generates a separate test signal each time said output signal traverses the band-pass of said resonant circuit means and while the amplitude of the frequency-modulated signals translated by said resonant circuit means is above said preset level, and said third circuit means includes a converter circuit for converting the duration of said test signal into digital pulses and a counTer circuit for counting said digital pulses to provide an indication of the response of said resonant circuit means.

Claim 5

Apparatus as defined in claim 2 wherein: said control circuit means controls said oscillator means so that the frequency of said output signal is varied to periodically traverse the band-pass of said resonant circuit; said second circuit means includes a threshold circuit means for detecting when the amplitude of the signal received from said resonant circuit means exceeds said preset level and generating a substantially constant amplitude test signal each time said output signal traverses the band-pass of said resonant circuit and while the amplitude of the signal received from said resonant circuit means exceeds said preset level, and said third circuit means includes an integrator circuit for converting the time duration of said test signals into a direct current signal providing an indication of the response of said resonant circuit means.

Claim 6

Apparatus as defined in claim 1 including: circuit means coupled to said resonant circuit means for detecting when the frequency of said frequency-modulated signals is at the resonant frequency of said resonant circuit means to generate a control signal, and circuit means responsive to said control signal for measuring the frequency of said frequency-modulated signals provided by said first circuit means, to provide an indication of the resonant frequency of said resonant circuit means.

Claim 7

Apparatus as defined in claim 4 wherein: said oscillator means provides a substantially sinusoidal signal, and said threshold detector continues to provide said test signal as long as the amplitude of two consecutive cycles of the signal translated by said resonant circuit means exceeds said preset level.

Claim 8

Apparatus for providing an indication of the Q of a resonant circuit comprising: a controllable oscillator circuit for providing a periodic signal, the frequency of which is a function of a control signal applied thereto; circuit means for receiving circuit elements for forming a resonant circuit; control circuit means, coupled to apply control signals to said oscillator circuit for varying the frequency of said periodic signal to scan a preset range of frequencies including the resonant frequency of said resonant circuit; circuit means for applying said periodic signal to said resonant circuit for translation thereof; threshold circuit means coupled to said resonant circuit for determining when the amplitude of the periodic signal translated by said resonant circuit exceeds a preset level greater than zero and generating a test signal corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means measuring the time duration of said test signal for providing an indication of the Q of said resonant circuit.

Claim 9

Apparatus for providing an indication of the Q of a resonant circuit comprising: a controllable oscillator circuit for providing a periodic signal, the frequency of which is a function of a control signal applied thereto; circuit means for receiving circuit elements for forming a resonant circuit; control circuit means, coupled to apply control signals to said oscillator circuit for varying the frequency of said periodic signal to scan a preset range of frequencies including the resonant frequency of said resonant circuit; circuit means for applying said periodic signal to said resonant circuit for translation thereof; threshold circuit means coupled to said resonant circuit for determining when the amplitude of the periodic signal translated by said resonant circuit exceeds a preset level greater than zero and generating a test signal corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means measuring the time duration of said test signal for providing an indication of the Q of said resonant circuit.

Claim 10

Apparatus as defined in claim 7 including: switching circuit means coupled to said circuit means for receiving said circuit elements for forming the resonant circuit for monitoring the amplitude of the signals translated by the resonant circuit and providing a control signal when a decrease in signal amplitude is detected, and circuit means coupled to said oscillator circuit and said switching circuit means for measuring the frequency of said oscillator circuit in response to the occurrence of said control signal.

Claim 11

Apparatus as defined in claim 7 wherein said circuit means responsive to said test signal includes: circuit means for integrating said test signal to provide a direct current signal having a magnitude corresponding to the time duration of said test signal, and indicator means receiving said direct current signal for providing an indication of the Q of the resonant circuit.

Claim 12

Apparatus as defined in claim 7 wherein said circuit means responsive to said test signal includes: integrator circuit means for integrating saId switching signal to provide a direct current signal having a magnitude corresponding to the time duration of said test signal, and a switching circuit coupled to said integrator circuit responsive to the magnitude of said direct current signal for providing an indication when the Q of said resonant circuit is above or below a preset value.

Claim 13

Apparatus as defined in claim 8 wherein said circuit means responsive to said switching signal includes: a clock circuit for providing clock pulses; a countercircuit, and switching circuit means coupled to said threshold circuit means, said clock circuit and said countercircuit for applying the clock pulses to said countercircuit for the duration of said test signal so that said counter circuit provides an indication of the Q of the resonant circuit.

Claim 14

Apparatus for determining the frequency response characteristics of a resonant circuit comprising: first circuit means for providing frequency-modulated cyclic signals; second circuit means adapted to be connected to a resonant circuit; third circuit means for applying the frequency-modulated signals to said second circuit means for translation by a resonant circuit connected to said second circuit means; peak detection circuit means including a pair of rectifier circuits coupled to separate filter circuits, wherein said rectifier circuits are coupled to said second circuit means for rectifying the signal translated by a resonant circuit connected to said second circuit means and including comparison circuit means coupled to receive filtered rectified signals from said filter circuit and generating a switching signal when a decrease in the translated signal amplitude occurs; fourth circuit means responsive to said switching signal, coupled between said first circuit means and said peak detection circuit means, for controlling said first circuit means for maintaining the frequency of the cyclic signals substantially constant at its frequency at the time of the occurrence of said switching signal, and fifth circuit means for measuring said substantially constant frequency in response to said switching signal.

Claim 15

Apparatus for determining the frequency response characteristics of a resonant circuit comprising: first circuit means for providing frequency-modulated cyclic signals; second circuit means adapted to be connected to a resonant circuit; third circuit means for applying the frequency-modulated signals to said second circuit means for translation by a resonant circuit connected to said second circuit means; peak detection circuit means including a pair of rectifier circuits coupled to separate filter circuits, wherein said rectifier circuits are coupled to said second circuit means for rectifying the signal translated by a resonant circuit connected to said second circuit means and including comparison circuit means coupled to receive filtered rectified signals from said filter circuit and generating a switching signal when a decrease in the translated signal amplitude occurs; fourth circuit means responsive to said switching signal, coupled between said first circuit means and said peak detection circuit means, for controlling said first circuit means for maintaining the frequency of the cyclic signals substantially constant at its frequency at the time of the occurrence of said switching signal, and fifth circuit means for measuring said substantially constant frequency in response to said switching signal.

Claim 16

Apparatus for determining the frequency response of a band-pass resonant circuit comprising: circuit means for applying a cyclic signal to said resonant circuit that varies in frequency at a preset rate to traverse the band-pass of said resonant circuit; circuit means coupled to said resonant circuit for determining when the amplitude of the cyclic signal passed by the resonant circuit exceeds a preset amplitude greater than zero and providing a control signal having a time duration corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means receiving said control signal and measuring the time duration of said control signal.

Claim 17

Apparatus for determining the frequency response of a band-pass resonant circuit comprising: circuit means for applying a cyclic signal to said resonant circuit that varies in frequency at a preset rate to traverse the band-pass of said resonant circuit; circuit means coupled to said resonant circuit for determining when the amplitude of the cyclic signal passed by the resonant circuit exceeds a preset amplitude greater than zero and providing a control signal having a time duration corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means receiving said control signal and measuring the time duration of said control signal.

Claim 18

Apparatus for detecting a change in the frequency response of a band-pass resonant circuit comprising: circuit means for applying a cyclic signal to said resonant circuit that varies in frequency in a predetermined manner to traverse the band-pass of said resonant circuit; circuit means coupled to said resonant circuit for determining when the amplitude of the cyclic signals passed by said resonant circuit exceeds a preset amplitude greater than zero and providing a control signal having a time duration corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means coupled to receive said control signal for measuring a change in the time duration of said control signal.

Claim 19

Apparatus for detecting a change in the frequency response of a band-pass resonant circuit comprising: circuit means for applying a cyclic signal to said resonant circuit that varies in frequency in a predetermined manner to traverse the band-pass of said resonant circuit; circuit means coupled to said resonant circuit for determining when the amplitude of the cyclic signals passed by said resonant circuit exceeds a preset amplitude greater than zero and providing a control signal having a time duration corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means coupled to receive said control signal for measuring a change in the time duration of said control signal.

Claim 24

Control apparatus comprising: inductive means; capacitive means; circuit means connecting said inductive means and said capacitive means in a resonant circuit exhibiting a band-pass characteristic the amplitude of which varies as a function of objects positioned in the vicinity of at least one of said capacitive means and said inductive means; means for applying a periodically reoccurring frequency-modulated signal to said resonant circuit; threshold circuit means coupled to receive signals passed by said resonant circuit to determine when the amplitude of the signal passed by the resonant circuit exceeds a preset level and for generating a control signal having a time duration corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means coupled to receive said control signal for measuring the time duration thereof and providing an indication when an object in the vicinity of at least one of said capacitive means and said inductive means changes the amplitude of said band-pass characteristic.

Claim 25

Control apparatus comprising: inductive means; capacitive means; circuit means connecting said inductive means and said capacitive means in a resonant circuit exhibiting a band-pass characteristic the amplitude of which varies as a function of objects positioned in the vicinity of at least one of said capacitive means and said inductive means; means for applying a periodically reoccurring frequency-modulated signal to said resonant circuit; threshold circuit means coupled to receive signals passed by said resonant circuit to determine when the amplitude of the signal passed by the resonant circuit exceeds a preset level and for generating a control signal having a time duration corresponding to the time period the signal translated by said resonant circuit exceeds said preset level, and circuit means coupled to receive said control signal for measuring the time duration thereof and providing an indication when an object in the vicinity of at least one of said capacitive means and said inductive means changes the amplitude of said band-pass characteristic.