| 摘要 |
1,193,011. Digital transmission systems. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 22 Jan., 1968 [24 Jan., 1967], No. 3247/68. Heading H4P. A regenerative repeater for bipolar data includes a clock pulse recovery circuit comprising a differentiator 12, full wave rectifier 4, threshold unit 5, and tuned circuit 7. Circuit 7 generates a clock frequency at the element rate of the signal to be regenerated and applies it via phase shifter 8 and shaper 9 to gating unit 2 which delivers the reshaped bipolar data. The threshold unit 5 passes only pulses corresponding to transitions in the bipolar data directly between positive and negative signal elements, and vice versa. The data is also limited at 13 and fed to differentiator 14 and rectifiers 15, the resulting needle pulses being gated at 16 with the relatively wide pulses from the threshold unit 5. To counteract the fall in output of tuned circuit 7 when the time between successive position-negative transitions is long, the output is rectified at 20 and filtered at 21. The resulting D.C. signal controls the threshold level of a threshold unit 19 which is fed by the rectified bipolar data. When the output of circuit 7 falls, the threshold level is reduced and the peaks in the rectified data pass to circuit 7 to excite it and increase its output voltage. |
