Adaptive AFT system with variable step resolution

Details Adaptive AFT system with variable step resolution Adaptive AFT system with variable step resolution

1991-10-24

1993-08-03

Groody, James J.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

3581911, 4551841, 4551641, 4551822, H04N 550

Patent

active

052334252

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.

REFERENCES:
patent: 4241450 (1980-12-01), Blatter et al.
patent: 4358791 (1982-11-01), French
patent: 4422096 (1983-12-01), Henderson
patent: 4564862 (1986-01-01), Cohen
patent: 4575761 (1986-03-01), Carlson et al.
patent: 4689685 (1987-08-01), Testin et al.
patent: 4698680 (1987-10-01), Lewis, Jr. et al.

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