PURPOSE: To attain the transmission of a broad band signal without effect of loopback by deciding a sampling phase of each band so that a loopback component caused in each sub band is cancelled thereby using a transmission line of a narrower band width than that of a broad band signal desired to be sent.
CONSTITUTION: A signal from a signal source 2 is divided into sub-bands by using a low pass filter 10, a medium band filter 8 and a high pass filter 6. When a sampling signal at a low frequency is used for a reference phase, since it is required to make sampling necessary for the transmission of a signal whose frequency is, e.g. 3MHz with a lag of 180° and 90° for high and medium frequencies respectively, the sampling is required at a frequency larger than a sampling frequency 6MHz, in this case, 24MHz or 6MHz. Then a prescribed signal is obtained by using an interpolation filter to sample the component of low, medium and high frequencies with a prescribed relation of phase. A decoder section 60 applies filtering to the component of each band for interpolation and the components of each band are added.
ENAMI KAZUMASA
ITO YASUMASA
