Digital automatic frequency control with tracking
US4498191A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 6, 1983 |
| Grant date | Feb 5, 1985 |
| Priority date | — |
| Expiry date | Jun 6, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03J1/0091
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A microprocessor controlled phase locked loop tuning system is disclosed which uses a single AFC detector whose threshold is controlled by the microprocessor. The system comprises a microprocessor (10) which provides frequency data to the PLL (11), and this data controls a programmable frequency divider in the PLL which determines the nominal frequency of a VCO (131) in the tuner (13). An AFC detector (141) in the intermediate frequency section (14) provides an AFC voltage output to the single comparator (15). The comparator produces a logic "0" or a logic "1" output to the microprocessor depending on whether the output from the AFC detector is above or below a predetermined threshold. The microprocessor is first operated in a frequency search mode to increase or decrease the frequency of the VCO in predetermined frequency increments depending on the logic state of the output of the comparator (15). During this mode of operation, the microprocessor may be programmed to respond to a change of state of the output of the detector by causing the frequency of the VCO change in the opposite direction to produce a successive predetermined number of detector output state changes and also t…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.