FREQUENCY-FOLLOWING INJECTION LOCKING OSCILLATOR.

Injection locking is currently in wide use in microwave communication amplifiers to provide improved noise performance. This amplifier, however, has limited locking range, and when the injection frequency falls outside the locking range, the circuit ceases to operate as a locking oscillator. The authors have considered a circuit which involves the addition of a frequency-tracking circuit to the injection locking oscillator. In the frequency-tracking oscillator, a voltage-controlled oscillator (VCO) is used as the oscillator and the bias voltage is adjusted so that the VCO self-excitation frequency is the same as the input signal frequency. It has been found that the locking range of this dual circuit is unlimited. Further, by changing the tracking speed, the circuit can be used as either an amplifier or a noise-improvement circuit.