Apparatus and method for sensing a rearward facing child seat using beat frequency detection

Abstract

An apparatus (,) senses the presence of a rearward facing child restraint seat (,) in a vehicle. Signal generating components (,and,) of a driver/receiver circuit (,) provide an electrical transmit signal, at a first frequency, which is applied to an antenna (,) during a first time period. The antenna (,) transmits an electromagnetic (EM) signal (,) at the first frequency during the first time period. At the end of the first time period, the EM transmit signal (,) is terminated. During a second time period, a component (,) of the driver/receiver circuit (,) provides a signal at a second, different frequency. An identification tag (,) is securable to the child restraint seat (,) and provides an EM return signal (,) in response to the EM transmit signal (,). The EM return signal (,) has the same frequency as the EM transmit signal (,) and continues past the termination of the EM transmit signal into the second time period. The antenna (,) receives the EM return signal (,) and provides an electrical return signal in response to the EM return signal. A mixer (,) is coupled to receive both the second frequency signal and the electrical return signal in the second time period, and provides a beat frequency signal. The presence and duration of the best frequency signal is indicative of the presence of the identification tag (,).