The present invention makes it possible to maintain the continuity of reception detection level and adjust the direction of a reception antenna even under the condition that the reception electric field is low and clock timing synchronization at a C/N ratio of 0 dB or less is lost. QAM modulation including a pilot carrier has higher correlativity in one symbol (1152 samples) correlation, and differential modulation with no pilot has higher correlativity in effective symbol (1024 samples) correction. Detection circuits are provided separately for the QAM modulation and the differential modulation, and in the differential modulation, autocorrelation with a 1024 FFT clock delay signal is performed. The higher of the respective correlation results is selected in the final stage.