A radio apparatus that performs communications using a random access method, such as a wireless LAN, is required to keep awaiting a signal, since it is not known when the signal is transmitted. In general, a period of time for awaiting a signal is longer than period of time for receiving a signal. In order to reduce power consumption of the whole radio apparatus, it is important to reduce power consumption during standby time.
As a method for reducing power consumption of a radio apparatus, for example, a method for improving a configuration of a synchronizing circuit in a digital demodulating unit is known (see for example, Milos Krstic, et. al., “Optimized low-power synchronizer design for the IEEE 802.11a standard,” ICASSP 2003 pp. 333-336.).
However, the method described in the Non-Patent Document 1 has a problem such that power consumption of an analog demodulating unit in a receiving unit, cannot be reduced while power consumption of a digital demodulating unit in the radio apparatus can be reduced.
The analog demodulating unit consumes as much power during standby time as when receiving a signal. Therefore, it is desired to reduce power consumption when the analog demodulating unit is in standby state in order to attain lower power consumption of the radio apparatus.