Method and apparatus for eliminating DC offset for digital I/Q demodulators
US5548244A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Nov 14, 1994 |
| Grant date | Aug 20, 1996 |
| Priority date | — |
| Expiry date | Nov 14, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D7/161
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A method and apparatus utilizing the techniques of frequency shifting and filtering for converting an input signal having a desired signal at intermediate frequency and an undesired DC offset to a baseband frequency signal in which the undesired DC offset is eliminated. The apparatus includes a first multiplier for multiplying the input signal by a signal having substantially the same intermediate frequency plus an offset frequency (.DELTA.f) to produce a first output signal wherein the desired signal is shifted in frequency to the offset frequency (.DELTA.f) and the undesired DC offset is unaffected. The apparatus also includes a second multiplier coupled to the first multiplier for multiplying the first output signal by a signal having substantially the same offset frequency (.DELTA.f) to produce a second output signal having the desired signal shifted to baseband frequency and the undesired DC offset shifted in frequency to the offset frequency .DELTA.f. In addition, a filter coupled to the second multiplier filters the output signal to remove the undesired DC offset while leaving the desired signal, now located at baseband frequency, intact.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.