Patent ID: 6965653

Claim:
An injection-locked demodulator circuit with Automatic Frequency Control (AFC), comprising: an injection-locked oscillator having a first input for receiving a modulated signal; a multiplier having a first input for receiving the modulated signal and a second input for receiving a signal generated by the injection-locked oscillator; a tuning circuit coupled to an output of the multiplier for receiving first and second input signals, the tuning circuit disabling the AFC until a difference in the first and second input signals reaches a threshold value, the tuning circuit comprising: first and second current mirrors coupled between a first input terminal that receives the first input signal and the output of the tuning circuit, the first current mirror receiving a first current and the second current mirror providing a first portion of an output current; third, fourth and fifth current mirrors coupled between a second input terminal that receives the second input signal and the output terminal of the tuning circuit, the third current mirror receiving a second current and the fifth current mirror providing a second portion of the output current, wherein the first and second input terminals receive a differential signal from the multiplier; and first and second transistors coupled from inputs of the respective second and fourth current mirrors to a first power supply conductor for preventing the second current mirror from providing the first portion of the output current and the fifth current mirror from providing the second portion of the output current; and a filter having an input coupled to an output of the tuning circuit and an output coupled to a second input of the injection-locked oscillator.