Frequency modulated solid state crystal oscillator providing a plurality of center frequencies

Claim 2

In a frequency modulated oscillator having an electron device for sustaining oscillations and a frequency determining circuit connected to the electron device, such frequency determining circuit including in combination: voltage variable capacitance means having first and second electrodes and providing different values of capacitance between said first and second electrodes in response to voltages of different magnitudes applied thereacross, means coupling said first electrode to the electron control device; switch means having a first terminal coupled to said electrode, a plurality of second terminals, and a switchable member arranged to selectively connect said first terminal to any one of said plurality of second terminals; means providing a reference potential; a plurality of networks each including a piezoelectric element connected in series with inductor means, said piezoelectric element being operated in a series resonant mode, each of said plurality of networks being connected between one of said plurality of second terminals of said switch means and said reference potential means so that a selected one of said networks is coupled to said voltage variable capacitance means by said switchable member; a series circuit having a resonant frequency which establishes the center frequency of oscillation of the oscillator and including said voltage variable capacitance means connected to said selected one of said networks; and modulating voltage supply means providing a modulating voltage, means coupling said modulating voltage supply means to said series circuit and applying said modulating voltage thereacross, said voltage variable capacitance means being responsive to said modulating voltage to change its said capacitance therewith to deviate the frequency of oscillation about said center frequency.

Claim 3

A frequency modulated crystal controlled oscillator including in combination: an electron device having a first electrode and a second electrode; means providing a reference potential; first capacitor means connected between said means providing the reference potential and said first electrode; second capacitor means connected between said first electrode and said second electrode; third capacitor means having first and second plates, said first plate being connected to said second Electrode; varactor means having an anode terminal and a cathode terminal, one of said anode and cathode terminals being directly connected to said second plate of said third capacitor means so that said varactor means is coupled through said third capacitor means to said second electrode; switch means having a first terminal connected to the other of said anode and cathode terminals, a plurality of second terminals and a switchable member for connecting a selected one of said plurality of said second terminals to said first terminal; a plurality of networks each including a piezoelectric element subject to operating in spurious modes of oscillation, said piezoelectric element being connected from said means providing the reference potential to a circuit junction, first resistive means connected in parallel with said piezoelectric element for damping out said spurious modes of oscillation, inductor means connected between said circuit junction and one of said plurality of output terminals of said switch means; a series resonant circuit comprised of said first capacitor means, said second capacitor means, said third capacitor means, said switchable member and said varactor means, for determining a selected center frequency of oscillation of said oscillator; and modulating voltage supply means providing a modulating voltage at its output, first circuit means connected between said one of said anode and cathode terminals of said varactor means and said output of said modulating voltage supply means so that a modulating voltage is supplied to said varactor means which deviates the frequency of oscillation of the oscillator about said selected center frequency.

Claim 4

A frequency modulated crystal controlled oscillator including in combination: an electron device having a first electrode and a second electrode; means providing a reference potential; first capacitor means connected between said means providing the reference potential and said first electrode; second capacitor means connected between said first electrode and said second electrode; third capacitor means having first and second plates, said first plate being connected to said second Electrode; varactor means having an anode terminal and a cathode terminal, one of said anode and cathode terminals being directly connected to said second plate of said third capacitor means so that said varactor means is coupled through said third capacitor means to said second electrode; switch means having a first terminal connected to the other of said anode and cathode terminals, a plurality of second terminals and a switchable member for connecting a selected one of said plurality of said second terminals to said first terminal; a plurality of networks each including a piezoelectric element subject to operating in spurious modes of oscillation, said piezoelectric element being connected from said means providing the reference potential to a circuit junction, first resistive means connected in parallel with said piezoelectric element for damping out said spurious modes of oscillation, inductor means connected between said circuit junction and one of said plurality of output terminals of said switch means; a series resonant circuit comprised of said first capacitor means, said second capacitor means, said third capacitor means, said switchable member and said varactor means, for determining a selected center frequency of oscillation of said oscillator; and modulating voltage supply means providing a modulating voltage at its output, first circuit means connected between said one of said anode and cathode terminals of said varactor means and said output of said modulating voltage supply means so that a modulating voltage is supplied to said varactor means which deviates the frequency of oscillation of the oscillator about said selected center frequency.

Claim 5

The oscillator of claim 2 wherein said first circuit means includes: fourth capacitor having first and second plates, said first plate of said fourth capacitor means being coupled to said output of said modulating voltage supply means; second resistor means having a first end connected to said second plate of said fourth capacitor means and a second end connected to said varactor means so that said modulating voltage is applied through said fourth capacitor and said second resistor to said varactor means; direct current bias source; and third resistor means connected from said direct current bias source to said first end of said second resistor means so that a quiescent bias voltage is supplied from said bias source to said varactor means through said second and third resistor means.

Claim 6

The combination of claim 1 wherein said inductor means is variable to change said resonant frequency of said series tuned circuit and to thereby adjust said center frequency of oscillation of the oscillator.

Claim 7

The combination of claim 1 wherein each of said piezoelectric elements is capable of operating at spurious modes of oscillation, and further including, direct current supply connected to said voltage variable capacitance means and providing a direct current bias voltage thereto, a plurality of first resistor means each connected directly across each of said piezoelectric elements to reduce said spurious modes of oscillation and to provide a direct current path for said voltage variable capacitance means.

Claim 8

The combination of claim 1 wherein said piezoelectric elements of said networks are quartz crystals having different frequencies of oscillations with respect to each other.

Claim 9

An oscillator in accordance with claim 2 wherein said electron device is a transistor and said piezoelectric elements are quartz crystals.

Claim 10

An oscillator in accordance with claim 2 wherein said inductor means is variable to change the tuning of said series resonant circuit to thereby adjust said center frequency of oscillation of the oscillator.