Communication processing apparatus and distance measuring method for communication processing apparatus

摘要

The distance to a tag is measured precisely without compromising the efficiency of the communication processing. A communication processing apparatus 1 alternately executes transmitting a carrier wave carrying a command and receiving a response from a tag 2 while transmitting an unmodulated carrier wave (CW). A transmission control unit 111 switches the phase of the unmodulated carrier wave transmitted from a transmission/ reception circuit 100 in response to start of reception of the reflected wave from the tag 2. The transmission/reception circuit 110 includes a circuit for separating and detecting an I signal and a Q signal included in the reflected wave from the tag 2. A phase detection unit 112 uses the I signal and the Q signal to detect change of the phase of the reflected wave. A distance calculation unit 113 measures a time from switching the phase of the unmodulated carrier wave to detecting the corresponding change in the phase of the reflected wave, and uses the time to calculate the distance from the antenna 10 to the tag 2.