Automatic frequency control with adjacent channel interference protection
US5774799A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 18, 1996 |
| Grant date | Jun 30, 1998 |
| Priority date | — |
| Expiry date | Apr 18, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03J1/0008
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A robust automatic frequency control (AFC) loop for use in radio frequency systems performs a threshold test on the accumulated error adjustments for controlling a frequency oscillator. Based on this test, the loop adjusts the value contained in the error accumulator to allow the receiver to remain locked to a desired frequency carrier even in the presence of a strong adjacent channel interferer. The AFC loop is designed to be used in error systems where the predetermined fixed carrier spacing. Assuming that the initial frequency error is never exceeded by one-half the carrier spacing, the system can determine if the wrong channel has been locked to if the oscillator in the AFC loop is corrected by more than half the carrier spacing. Through use of a threshold test on the accumulative oscillator correction, the AFC loop can determine if the receiver has locked to an adjacent interfering channel. Having determined such a lock has occurred, the oscillator can be adjusted by plus or minus one channel, thus reestablishing connection of the AFC loop to the desired channel.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.