Disclosed is a method that preferably performs transmission processing to a time sequence signal of a known pattern as the pre-amble and an OFDM transmitted signal. In data communications, the general practice defines the pre-amble and detects the peaks of the mutual correlation to thereby detect synchronization. The pre-amble here is defined by the binary value in most cases for simplification of a correlation detecting device. In this case, the spectrum becomes irregular with sharp peaks and dips, which deteriorates the correlation characteristic. The method of the invention forcibly adjusts the spectrum amplitude of the pre-amble pattern on the transmitting side while retaining the phase information thereof, and thereby the method improves the spectrum and correlation characteristics while securing simplification of a correlation detecting device on the receiving side.