Voltage controlled oscillator using a voltage tunable filter with feedback

Claim 1

A voltage controlled oscillator for producing a variable frequency output signal in response to the magnitude of an input control signal comprising: (a) a tunable filter circuit for simulating a resistance--inductance--capacitance circuit having a resonant frequency which is adjustable in response to said input control signal, said filter circuit comprising, (1) circuit means for providing at its output a first signal representative of the voltage of the inductance of the simulated circuit in response to a feedback signal, a signal representing the capacitance voltage and a signal representing the resistance voltage, (2) a first gain path including first multiplying means responsive to said first signal and said input control signal to provide a signal proportional to the product thereof, (3) a second gain path for providing an output signal proportional to said first signal, (4) first integrating means responsive to the output signals of said first and second gain paths to develop said variable frequency output signal proportional in magnitude to the resistance voltage of the simulated circuit and in frequency to the extant value of said input control signal, (5) third gain path means including second multiplying means responsive to said signal proportional to the resistance voltage and said input control signal to provide an output signal, (6) fourth gain path means for providing an output signal proportional to said signal proportional to the resistance voltage, (7) second integrating means responsive to the output signals of said third and fourth gain paths to develop a signal proportional to the capacitance voltage of said simulated circuit; and, (b) feedback means including a signal limit circuit responsive to the signal representing the resistance voltage for providing said feedback signal.