| 摘要 |
1323446 Automatic phase control INTERNATIONAL BUSINESS MACHINES CORP 26 Nov 1970 [15 Dec 1969] 56356/70 Heading H3A A data communication system including signal sampling means is characterized in that the sampling time is controlled by a circuit which includes means for differentiating an input to the sampling means and means for combining the differentiated signal with the output from the sampling means to produce the sample time control signal. Amplitude modulated data signals from input 21 are fed to demodulators 25, 49 together with in-phase and quadrature carrier signals from local carrier source 47. The two demodulated signals are sampled and the resulting sampled signals are fed to a comparator 53 to produce an error signal for controlling the phase of the carrier source 47. The signal from demodulator 25 is also fed to a second comparator 55, the other input of which is derived from the differentiated and sampled output from the demodulator 25. The resulting output from the comparator 55 provides a control signal for correcting the sampling time. This signal is fed to a further comparator (85, Fig. 3, not shown) where it is compared with a ramp signal to produce a sampling pulse whenever the amplitudes of the ramp and error signal are equal. |
