PURPOSE: To make realization of hardware easy and to reduce errors in data by giving spectrum shaping characteristic for shaping transmission characteristic from the input end of a modulating circuit section to the output end of a demodulating circuit section to desired characteristic to at least one of a polyphase filter and an inserted filter in a transmultiplexer of transmitting side or receiving side.
CONSTITUTION: When spectrum shaping characteristic of roll-off characteristic HR for, for instance, PSK wave is requested to the receiving side, characteristic of the polyphase filter and inserted filter 4 is determined to, for instance, HR= HI.HT. That is, characteristic of the two is determined to make synthetic transmission characteristic of the polyphase filter and inserted filter 4 have desired spectrum shaping characteristic. By this way, signals to the demodulating circuit 5 can be spectrum shaped without adding a filter for spectrum shaping specially, and demodulated and reproduced data can be taken out from the demodulating circuit 5 to an output terminal at low error rate.
NAKAMURA MAKOTO
SUZUKI HIDEO
TOSHIBA CORP