Conventional digital calibration type analog-to-digital converters cannot converge calibration within an preamble period of a packet signal. An analog-to-digital converter is subjected to digital calibration using a beacon signal, a polling signal, or another user signal or a signal applied from a transceiver side to a receiver side. Some or all of circuits are brought into a sleep mode in a period except data reception and the analog-to-digital converter calibration such that a signal monitor unit detects another signal to activate the circuit in the sleep mode for performing the calibration of the analog-to-digital converter for reducing the power consumption.