Adaptive AFT system with variable step resolution
US5233425A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Oct 24, 1991 |
| Grant date | Aug 3, 1993 |
| Priority date | — |
| Expiry date | Oct 24, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/50
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A frequency synthesis tuner for a television receiver includes a voltage controlled oscillator (VCO) responsive to a phase locked loop (PLL) for generating a local oscillator signal which is used to convert a received RF television signal to an intermediate frequency signal. An automatic fine tuning (AFT) detector develops an AFT error signal representing the frequency deviation of the converted signal from 45.75 MHz. Fine tuning is effected by controlling the reference and channel index dividers of the PLL in a coordinated manner in response to the AFT error signal for initially rapidly adjusting the frequency of the local oscillator signal to minimize the deviation of the converted signal from 45.75 MHz and then subsequently by further adjusting the frequency of the local oscillator signal in successive steps of adaptively increasing resolution. In one embodiment, the frequency of the local oscillator signal is adjusted in successive steps of adaptively increasing resolution as a function of the time rate of change of an autocorrelation signal developed in response to a received ghost cancellation reference (GCR) signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.