Patent attributes
A detector receiver circuit (2) for use as a wake-up detector for detecting an amplitude modulated carrier signal is described. The circuit (2) comprises: an antenna (4) for receiving the modulated carrier signal; a transistor (10), such as an FET, is connected to the antenna (4) and configured to operate as a detector of modulation of the carrier frequency. The circuit further comprises a resonator circuit (12-16) which is also connected to the transistor and configured such that the transistor (10) can simultaneously oscillate at substantially the modulation frequency; an oscillator quenching means (20) for periodically quenching oscillation of the transistor (10) and means (26, 28, 30) for sensing the characteristics of the build-up of oscillation to indicate the presence of a modulated carrier signal. How quickly the magnitude of oscillation of the transistor (10) builds up is dependent on whether the antenna is receiving a carrier signal which is modulated at the frequency of self-oscillation of the transistor and this is utilized to detect for the presence of a valid wake-up signal.
