Patent ID: 7639118

Claim:
A receiver circuit for detection of a modulated signal, comprising: an antenna configured to receive a modulated carrier signal having a modulation frequency; a transistor configured to receive the modulated carrier signal at its gate; a resonator circuit coupled to the transistor and configured to cause the transistor to oscillate at a predetermined oscillation frequency and to produce an oscillation signal having a magnitude that increases at a rate that is faster in the presence of the modulated carrier signal than in the absence of the modulated carrier signal; an oscillation quenching circuit configured to periodically quench oscillation of the transistor and to allow oscillation of the transistor for a time period that is less than required for the oscillation signal to reach a predetermined threshold in the absence of the modulated carrier signal; and an oscillation sensing circuit coupled to the transistor to receive the oscillation signal from the transistor and to sense if the oscillation signal reaches the predetermined threshold within the time period to indicate the presence of the modulated carrier signal having the modulation frequency.