公开(公告)号：JPH01319319A

公开(公告)日：1989-12-25

申请号：JP15123588

申请日：1988-06-21

Applicant: NEC CORP

Inventor： ICHIYOSHI OSAMU ,  KAWAUCHI TORU

IPC: H03H17/02

Abstract: PURPOSE:To select the transmission frequency band width and the frequency characteristic freely by using the 2nd high speed Fourier transformation device and the 2nd polyphase digital filter group so as to convert an input signal again into an analog signal. CONSTITUTION:After an input signal is converted at first into a digital signal by an A/D converter 4 in an FDM branch circuit 1, the signal is demultiplexed into N-set of frequency components by N-phase digital fiters(PDF) 5-1-5-N and the 1st high speed Fourier transformation device (FET) 6. The required component among N-set of frequency components, that is, the component desired to be transmitted is selected by a switch circuit 2. The signal from the switch circuit 2 is integrated into one carrier by the 2nd high speed Fourier transformation device (FET) 7 having the opposite function to the process of the FDM demultiplexing circuit 1 and the N-phase digital filters (PDF) 8-1-8-N in a group modulator 3 and D-A converted by a D/A converter 9. Thus, only a component of the frequency band selected by the switching circuit 2 is passed through.