| 摘要 |
PURPOSE:To economically construct the transmission system of a digital audio signal, by constituting a system so that the digital audio signal reproduced by a compact disk player is transmitted to a CATV line being left as an EFM modulation signal. CONSTITUTION:The EFM modulation signal(signal before applying EFM demodulation) is derived from a compact disk player 1, and its high frequency component is cut at a low-pass filter 3. The output of the low-pass filter 3 is impressed on an amplitude modulation circuit 4, and an IF frequency signal(carrier signal) outputted from an oscillation circuit 5 is amplitude-modulated based on the EFM modulation signal. The modulation signal passes through a residual sideband filter(VSBF) 6, and is impressed on a mixing circuit 7, and is mixed with a local oscillation frequency signal corresponding to each output channel outputted from a local oscillation circuit 8, and after passing through a band-pass filter 9, it is mixed with another CATV signal at a combiner, then it is sent to the CATV line.
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