process s 640 a deep fading and low sleep process s 650 a deep sleep process s 660 are performed on a case by case basis when the main demodulating process s 640 is started the controller 309 measures fpr n 1 fpr n 2 fpr n 3 and multiple paths s 641 subsequently the controller 309 compares fpr n with the first value s 642 if the fpr n is greater than the first reference value the controller 309 selects a dominant path estimated by the frame tracking unit s 643 and performs an ofdm signal demodulating process and a channel decoding process based on the dominant path s 644 the controller 309 determines signal quality q 1 based on the result of the channel decoding process s 645 at this time the reference for determining q 1 is as follows in the channel decoding process the controller 309 checks rs sync bytes or crc of packet or audio signals after a convolution decoding process at this time if half or more decoding errors determined in a signal arc generated the signal quality q 1 after the convolution decoding process is determined to be u201c bad u201d in step s 642 if the fpr n is smaller than the first reference value it can be determined as one of the following three cases a first case is when the strength of the input signal of a current frame is rapidly decreased a second case is a low sleep mode a third case is a deep sleep mode in the present invention unnecessary processes are not performed suitable for the respective cases so that power consumption can be reduced for.