Frequency modulated crystal controlled oscillator operable at a plurality of temperature compensated center frequencies

Claim 1

A frequency determining circuit facilitating the generation of any one of a plurality of selected center frequencies by a frequency modulated oscillator having a single electron device with first, second and third electrodes which sustains oscillation at one of the selected center frequencies, such frequency determining circuit including in combination: means providing a reference potential; first circuit means providing an equivalent capacitance and having first capacitor means directly connected between the first and third electrodes of the electron device, second capacitor means having first and second plates with said first plate connected to the first electrode of the electron device, voltage variable capacitor means connected from said refErence potential means to said second plate of said second capacitor means, inductor means and third capacitor means connected in series with each other across said voltage variable capacitor means; switch means having a first terminal connected to the third electrode of the electron device, a plurality of second terminals and a switchable member for connecting said first terminal to any one of said second terminals; a plurality of networks each including a piezoelectric element, means coupling each of said plurality of networks between one of said second terminals of said switch means and said reference potential means so that said switchable member connects a selected one of said piezoelectric elements to the third electrode of the electron device, each of said piezoelectric elements providing a value of inductance which resonates with said equivalent capacitance to provide a selected one of the different center frequencies when such piezoelectric element is connected by said switchable member of said switch means to said third electrode; and modulating voltage supply means providing a modulating signal across said third capacitor means and through said inductor means to said voltage variable capacitor means to change said equivalent capacitance thereof thus deviating said center frequency a predetermined amount in response to said modulating signal of a given amplitude.