Adjacent channel interference detection & suppression circuit
US5493717A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 31, 1994 |
| Grant date | Feb 20, 1996 |
| Priority date | — |
| Expiry date | May 31, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B2001/1054
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
FM radio receivers, particularly in moving vehicles, are subject to intermittent adjacent-channel interference. It is known to detect such interference and suppress it by narrowing bandwidth in the Intermediate Frequency (IF) signal path. However, it is desirable to again broaden the bandwidth once the interference has subsided. An improved system, which automatically and dynamically adjusts the bandwidth, employs first and second signal level evaluation circuits (11, 12), a comparison stage (13) which compares their outputs, and a variable-bandwidth filter stage (6, 14) controlled by the comparison stage. The comparison stage is programmed with a set of signal difference threshold values and corresponding filter bandwidth values, and controls the filter stage (6, 14) to adjust the bandwidth to the appropriate value, indicated by which signal difference threshold value has been exceeded. In a preferred embodiment, a second IF filter (15) does "double duty" as part of the variable-bandwidth filter stage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.