| 摘要 |
PURPOSE:To multiplex an analog and a digital signal through a single transmission line by inputting the analog signal and binary digital signal, extracting the digital signal on the basis of the difference in amplitude level, and clipping the difference in amplitude level and extracting a pulse-modulated signal. CONSTITUTION:A rectangular wave generating circuit 4 generates rectangular wave pulses of prescribed repetitive frequency with a specific amplitude level. Those are integrated by an integration circuit 42 to obtain a triangular wave. A pulse-width modulating circuit 5 samples the analog signal at a rising point of the rectangular wave and outputs a signal with logic H until the triangular wave coincides with the sampled value. A signal received through a transmission line 3 has amplitude levels V1 and V2. When reference voltages V3 and V4 of comparators 8 and 9 are so set that V3<V2 and V1>V4>V2, the comparator 8 clips the amplitude at V3 and outputs a pulse-width modulated signal with the same amplitude. This signal is smoothed by an LPF10 to obtain an analog output signal b1. The comparator 9, on the other hand, makes an amplitude discrimination so as to select only signals having amplitudes higher than V4. |
