A detector receiver circuit for use as a wake-up detector for detecting an amplitude modulated carrier signal includes an antenna for receiving the modulated carrier signal; and a transistor, such as an FET, which is connected to the antenna and configured to operate as a detector of modulation of the...http://www.google.com.hk/patents/US7046122?utm_source=gb-gplus-share專利 US7046122 - Receiver circuit
