FREQUENCY BAND LIMITING METHOD

PROBLEM TO BE SOLVED: To provide a frequency band limiting method for a transmission output waveform of a wireless transmitter, on which a modulator and an amplifier represented by a digital phase shift keying(PSK) system are mounted. SOLUTION: This method executes a 1st processing where digital phase shift keying is applied to a carrier with a base band signal without band limit, to obtain a modulation wave whose frequency spectrum is spread and a 2nd processing, where phase shift keying is applied to a carrier whose phase is delayed by 180-degrees with a base band signal from which a main signal component is eliminated to obtain a carrier with the same level as and an opposite phase to those of a side lobe component of the carrier obtained in the 1st processing. Then the carrier obtained by the 1st processing and the carrier obtained in the 2nd processing are coupled as a 3rd processing, to transmit a transmission signal, the spread of the frequency spectrum of which is suppressed is sent to an antenna.