Voltage controlled oscillator for integrated circuit fabrication

Claim 1

A voltage controlled r.f. oscillator comprising: a. a first circuit branch having r.f. gain comprising a first pair of transistors in an upper rank having their emitters paired and connected to the collector of a third, lower rank transistor, b. a second circuit branch having r.f. gain comprising a second pair of transistors in an upper rank having their emitters paired and connected to the collector of a fourth, lower rank transistor, one collector of said first pair and one collector of said second pair being coupled to a common output load impedance. c. means coupling the emitters of said lower rank transistors to a common current source for balancing the emitter currents of said upper rank in response to base excitation of one lower rank transistor, said excitation ideally producing in said output load impedance an output signal from said first branch equal and 180* out of phase to that produced from said second branch, d. a phase shift network in said first branch coupled to the collector of said third transistor, which in response to base excitation thereof, reduces the phase difference between the currents in said two branches and appearing in said output load impedance to a value substantially below 180* but substantially in excess of 90*, e. a feedback path coupled between the load impedance and said base of said third transistor including a high Q resonant circuit for establishing resonant conditions substantially at the resonant frequency thereof but subject to pulling upon variation in the resultant phase shift in said r.f. gain branches, the accumulated parasitic delay around the loop at resonance, including forward and feedback paths, approximately one-half the phase difference between said individual branches to insure a regenerative feedback condition from currents in either branch; and f. means for applying an interbase D.C. control potential to each upper rank transistor pair, poled for double balanced operation to produce an r.f. output quantity whose phase is continuously variable within said phase difference from a virtual lead to a virtual lag, each being substantially less than 90*, for inducing a compensatory reactance change in said resonant circuit, and a corresponding change in the phase and frequency of resonance of said oscillator.