A wireless modem is mounted to a terminal for wireless communication, and specifically controls an internal drive clock to reduce power consumption in an active mode. The wireless modem includes: a wireless core module for transmitting and receiving a radio signal; a modulator for converting data to be transmitted into a wireless transmission signal and transmitting the converted signal to the wireless core module; a demodulator for converting the signal received from the wireless core module into reception data; a synchronizer for synchronizing the signal received from the wireless core module; and a clock controller for generating a drive clock of each of the modulator, the demodulator, and the synchronizer. A low power clock controller is divided into six main functional blocks of a synchronizer, an analog controller, a modulator, a channel decoder, a demodulator, and a channel encoder, and has a feature that a clock is input only when a main functional block operates. As a result, it is possible to minimize power consumption caused by clock switching when an Orthogonal Frequency Division Multiplexing Access (OFDMA) mobile station modem operates in an active mode through the clock controller.