Method and apparatus for automatic gain control and DC offset cancellation in quadrature receiver
US5617060A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 13, 1995 |
| Grant date | Apr 1, 1997 |
| Priority date | — |
| Expiry date | Apr 13, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D2200/0052
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An automatic gain control (AGC) and D.C. offset correction method and apparatus for controlling signal power of a received RF signal within a dual mode quadrature receiver is disclosed herein. In a preferred implementation the automatic gain control apparatus may be adjusted to provide a desired control response to various fading characteristics of a received FM, FSK, GMSK, QPSK, or BPSK signal. The AGC apparatus includes an adjustable gain amplifier having an input port for receiving an input signal, a control port for receiving a gain control signal, and an output port for providing an output signal. A quadrature downconverter coupled to the output port serves to translate the frequency of the output signal to a baseband frequency, thereby producing baseband signals. In a preferred implementation the downconverter is operative to map the carrier frequency of the output signal to a baseband frequency offset by a predetermined margin from D.C. Two high gain active lowpass filters provide out-of-band signal rejection for the baseband signals. A D.C. feedthrough suppression loop, disposed to receive said baseband signal, suppresses D.C. offsets produced by the downconverter and lowpa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.