Upstream frequency bandwidth of CATV is narrower and transmission rate is slower, compared to downstream channels. In general, high speed data transmission from subscribers to the central system has been demanded in areas such as the telemedicine using high quality video. We have developed a system with more than 200MHz upstream frequency bandwidth whose spectrum starts at 870MHz, by parallel connecting a existing trunk amplifier and a developed extension amplifier. To prevent interfarences between parallel connected two amplifiers, lowpass and highpass filters with sharp roll off are required. Instead of using filters with lumped elements which have difficulty in adjusting all elements values, we have been developing microstripline bandpass and bandstop filters with wideband and high selectivity. Transmission tests conducted with extension amplifiers with those filters over the CATV network show that 64QAM signals of 5Msymbols/sec can be transferred at frequency between 900MHz and 1.2GHz.
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