| 摘要 |
The fast tuning subsystem for switching television channels includes a tuner (124) having a VCO (130) responsive to voltage applied to its control input for determining the channel frequency the tuner (124) selectively receives. Predictive means (128, 140) supplies a selected predicted voltage signal, corresponding to a signal stored in memory (138), to the control input to slew the channel frequency rapidly to the corresponding selected frequency. An error detector (146, 148) generates a tuning error signal indicative of the error of the tuner with respect to the selected channel frequency. Feedback means (i.e., the phase locked loop (144)) combines the tuning error signal with the selected predicted voltage signal to provide a control signal to the VCO (130). The predictive means is substantially decoupled from the feedback means to prevent the slew mode from substantially perturbing the feedback mode. A method for predicting control voltages for slew control is also directed, preferably utilizing a combination binary and linear search. |
