Adjustable piezoelectric tunable oscillator for acoustic signal generating system

Claim 2

For use in the remote control of electrical apparatus, an acoustic signal generating system for generating a plurality of individually selectable, frequency-spaced sound signals, comprising: an electronic amplifier; feedback circuit means for providing positive feedback from a first port to a second port of said amplifier so as to cause said amplifier to be capable of oscillation; and means for determining the frequency of oscillation of the system and for generating spatial acoustic waves at the frequency of oscillation, including a piezoelectric transducer means coupled to said amplifier so as to affect the frequency of oscillation thereof, said piezoelectric transducer means having a high electro-mechanical coupling coefficient and coupled thereto selectively adjustable electrical reactance means for modifying the resonant frequency of said transducer means so as to cause the system to oscillate at a selected frequency.

Claim 3

The system defined by claim 1 wherein said reactance means has a reactance-versus-frequency characteristic which enables said system to be tuned to selected frequencies within a predetermined range of frequencies, said system including means for suppressing the capability of said system to oscillate at spurious frequencies outside said range, comprising isolated pick-up electrode means disposed on a portion of one vibratory surface of said transducer means for deriving a control signal which is of a phase effective to sustain osCillation at frequencies within said range, but of a phase which tends to suppress oscillation for frequencies outside said range.

Claim 4

An acoustic signal generating a system comprising: an electronic oscillator for developing a signal of a predetermined frequency; a piezoelectric transducer coupled to said oscillator so as to affect the frequency of oscillation thereof, said transducer exhibiting a substantial electro-mechanical coupling coefficient for controlling said frequency and for producing spatial acoustic waves; and selectively adjustable reactance means coupled across said transducer for modifying in discrete steps the resonant frequency of said transducer to cause said oscillator to oscillate at a selected signal frequency.

Claim 5

An acoustic signal generating a system comprising: an electronic oscillator for developing a signal of a predetermined frequency; a piezoelectric transducer coupled to said oscillator so as to affect the frequency of oscillation thereof, said transducer exhibiting a substantial electro-mechanical coupling coefficient for controlling said frequency and for producing spatial acoustic waves; and selectively adjustable reactance means coupled across said transducer for modifying in discrete steps the resonant frequency of said transducer to cause said oscillator to oscillate at a selected signal frequency.

Claim 6

A system as defined in claim 3 in which said reactance means is composed of a pair of reactive elements of opposite sign and one of which has a magnitude adjustable in discrete steps.

Claim 7

A system as defined in claim 4 in which said predetermined frequency lies within a range of frequencies around a center frequency and in which the other of said reactive elements has a magnitude at least approximately of a value to neutralize the mid-range magnitude of said one element at said center frequency.

Claim 8

A system as defined in claim 3 in which said adjustable reactance means includes the series combination of an inductor and a capacitor.

Claim 11

A system as defined in claim 6 in which said oscillator responds in frequency change to an adjustment in frequency of series resonance of said transducer; in which an inductance is coupled across said transducer for establishing therewith a reactance characteristic having a zero-value center frequency between a pair of pole frequencies; and the series-combination of said inductor and said capacitor are coupled in series between one side of said inductance and said oscillator.

Claim 12

A system as defined in claim 3 in which an inductance is coupled across said transducer for establishing therewith a reactance characteristic having a zero-value center frequency between a pair of pole frequencies; and which further includes means for suppressing the generation of a pair of spurious signals capable of being developed by said oscillator which individally have frequencies respectively above and below the upper and lower ones of said pole frequencies.

Claim 13

A system as defined in claim 9 in which said means for suppressing the generation of said spurious signals includes feedback means for feeding back to said oscillator a portion of the signal energy present in said transducer which is in phase with said oscillator for frequencies between said pole frequencies and out of phase for frequencies outside said pole frequencies.

Claim 14

A system as defined in claim 10 in which said feedback means includes an isolated electrode disposed on a portion of one vibratory surface of said transducer for sensing said signal energy and for feeding back a portion thereof to said oscillator.

Claim 15

A system as defined in claim 3 which further includes inverse-feedback means for suppressing a pair of spurious signals capable of being developed by said oscillator at frequencies respectively below and above said range.

Claim 16

For use in the remote control of electrical apparatus, an acoustic signal generating system for generating a plurality of individually selectable, frequency-spaced sound signals, comprising: an electronic amplifier; and feedback circuit means for providing positive feedback to cause said amplifier to be capable of oscillation, said feedback circuit means including a piezoelectric transducer having a high electro-mechanical coupling coefficient and coupled thereto selectively adjustablE electrical reactance means for modifying the resonant frequency of said transducer so as to cause the system to oscillate at a selected frequency, said piezoelectric transducer radiating spatial acoustic waves at said frequency of oscillation.

Claim 17

For use in the remote control of electrical apparatus, an acoustic signal generating system for generating a plurality of individually selectable, frequency-spaced sound signals, comprising: an electronic amplifier; and feedback circuit means for providing positive feedback to cause said amplifier to be capable of oscillation, said feedback circuit means including a piezoelectric transducer having a high electro-mechanical coupling coefficient and coupled thereto selectively adjustablE electrical reactance means for modifying the resonant frequency of said transducer so as to cause the system to oscillate at a selected frequency, said piezoelectric transducer radiating spatial acoustic waves at said frequency of oscillation.

Claim 18

For use in the remote control of electrical apparatus, an acoustic signal generating system for generating a plurality of individually selectable, frequency-spaced sound signals, comprising: an electronic amplifier; and feedback circuit means for providing positive feedback from a first port to a second port of said amplifier so as to cause said amplifier to be capable of oscillation, said feedback circuit means comprising: a piezoelectric transducer having a high electromechanical coupling coefficient and being capable of radiating spatial acoustic waves at its frequency of oscillation, selectively adjustable reactance means coupled to said transducer for modifying the resonant frequency of said transducer so as to cause the system to oscillate at a selected frequency, said reactance means having a reactance-versus-frequency characteristic which enables said system to be tuned to selected frequencies within a predetermined range of frequencies, and means for suppressing the capability of said system to oscillate at spurious frequencies outside said range, including isolated pick-up electrode means disposed on a portion of one vibratory surface of said transducer for deriving a control signal for application to said amplifier which is of phase to sustain oscillation for frequencies within said range, but of phase to suppress oscillation for frequencies outside said range

Claim 19

For use in the remote control of electrical apparatus, an acoustic signal generating system for generating a plurality of individually selectable, frequency-spaced sound signals, comprising: an electronic amplifier; and feedback circuit means for providing positive feedback from a first port to a second port of said amplifier so as to cause said amplifier to be capable of oscillation, said feedback circuit means comprising: a piezoelectric transducer having a high electromechanical coupling coefficient and being capable of radiating spatial acoustic waves at its frequency of oscillation, selectively adjustable reactance means coupled to said transducer for modifying the resonant frequency of said transducer so as to cause the system to oscillate at a selected frequency, said reactance means having a reactance-versus-frequency characteristic which enables said system to be tuned to selected frequencies within a predetermined range of frequencies, and means for suppressing the capability of said system to oscillate at spurious frequencies outside said range, including isolated pick-up electrode means disposed on a portion of one vibratory surface of said transducer for deriving a control signal for application to said amplifier which is of phase to sustain oscillation for frequencies within said range, but of phase to suppress oscillation for frequencies outside said range