Method and apparatus for reducing FM intrusion in AM receivers
US5937337A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 23, 1996 |
| Grant date | Aug 10, 1999 |
| Priority date | — |
| Expiry date | Sep 23, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D5/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A technique for reducing FM intrusion in an AM section of an AM/FM receiver. In one embodiment, a first switch is provided between an FM tuner filter circuit and an AM tuner circuit. A second switch is provided between the FM tuner circuit and a reference potential. When the receiver is in an FM mode, the first switch is closed so that a tuning voltage can be applied to the FM tuner circuit, and the second switch is open to prevent the tuning voltage from being affected by the reference potential. When the receiver is switched to the AM mode, the first switch is open to prevent intermodulation product signals generated by the FM tuner circuit from reaching the AM tuner circuit, and the second switch is closed to connect the FM tuner circuit to the reference potential. By connecting the FM tuner circuit to the reference potential when the receiver is in the AM mode, the tuning of the FM tuner circuit is shifted out of the FM bandwidth, thus eliminating intermodulation products at the AM frequencies. In an alternate embodiment, a switch is provided to switch off the power to the FM front end when in the AM mode.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.