PURPOSE: To reduce greatly the number of arithmetic circuits, by turning the complex signal of a time-division multiplex signal into a noncyclic digital filter signal in correspondence to channels and then synthesizing the noncyclic digital output signal connected to the output side to change it into a frequency-divided multiplex signal.
CONSTITUTION: The outputs Y1r, Y1i, Y2r and Y2i of a noncyclic digital FIR filter having a 16kHz action of the time-division multiplex TDM signal are applied to input terminals 4-1∼4-4 and then added together through adders 4-5∼4-8. The outputs of this addition are led to adders 4-13 and 4-14 via FIR filters 4-9∼4-12 having a 112kHz action. The outputs of these adders are synthesized by a synthesizing circuit 4-17 via multiplying circuits 4-15 and 4-16 to be delivered in the form of a frequency-divided FDM signal. In this case, the output is calculated just with every two times through the filters 4-9∼4-12 to reduce the number of arithmetic circuits down to 1/2. In the same way, the number of arithmetic circuits can be reduced also in case the FDM signal is converted into the TDM signal.
MURANO KAZUO
SOEJIMA TETSUO
AOYAMA TOMONORI
YOSHIMURA HIROSHI
WAKABAYASHI KIYOHISA
NIPPON TELEGRAPH & TELEPHONE