Method and apparatus for eliminating interference due to spurious signals generated in synthesized receivers
US4545072A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 5, 1983 |
| Grant date | Oct 1, 1985 |
| Priority date | — |
| Expiry date | Dec 5, 2003 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B15/06
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A synthesizer radio frequency (RF) signal receiver (FIG. 1) for single sideband radios is described that can eliminate interference due to internally generated spurious signals, commonly referred to as "whistler spurs". The unique receiver includes first and second mixers (102 and 106), which are intercoupled by a 75 mHz crystal filter (104) having a 20 kHz passband, and which are each coupled to signals from voltage controlled oscillators (120 and 140). The first IF frequency provided by the first mixer (102) varies about 75 mHz, and the second IF frequency provided by the second mixer (106) is fixed at 11.4 mHz. The second mixer (106) is coupled to 11.4 mHz stages (108) which have a 2.7 kHz passband. The 11.4 mHz stages (108) are followed by another mixer (110) and audio stages (112) for demodulating audio signals from the received RF signal, which are then applied to a speaker (114). The frequency of the VCO (120) coupled to the first mixer (102) can be varied by changing the divisor N of a programmable divider (123), and the frequency of the VCO (140) coupled to the second mixer (106) likewise can be varied by changing the divisor M of a programmable divider (133). When interfe…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.