Double superheterodyne tuner
US4553264A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 19, 1983 |
| Grant date | Nov 12, 1985 |
| Priority date | — |
| Expiry date | Sep 19, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D7/18
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
In a double superheterodyne tuner, the first local oscillator frequency is set to a value higher than the first intermediate frequency, which is set to a value between three and five times the upper limit of the receiving frequency range. With this arrangement spurious signals of at least third or less order can be prevented from occuring in the first intermediate frequency range. The tuner comprises an input filter which attenuates interference signals whose harmonics equal a desired frequency. The second intermediate frequency may be selected such that it is obtained by subtracting the second local oscillator frequency from the first intermediate frequency which is higher than the second local oscillator frequency. As a bandpass filter for passing the first intermediate frequency may be used a coaxial dielectric filter so as to reduce interferences by undesired channel signals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.