Injection locked oscillator lock detector

A simple circuit that is able to indicate if an injection-locked oscillator is in the locked condition by providing a ‘high’ or ‘low’ output is presented. The detector is compatible with most injection-locked oscillators as all that is required is access to the low-frequency bias circuit, with no direct access needed to the RF/microwave signals. To prove the universal nature of the lock detector it is successfully demonstrated practically for two scenarios: (i) a 1 GHz injection-locked VCO and (ii) a 60 GHz SiGe VCO MMIC.