Intermodulation distortion reduction circuit utilizing variable attenuation
US5697081A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 13, 1995 |
| Grant date | Dec 9, 1997 |
| Priority date | — |
| Expiry date | Dec 13, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B1/109
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A variable attenuator circuit provides variable attenuation responsive to received signal strength in a receiver to reduce intermodulation (IM) distortion. In a dual-mode frequency modulation/code division multiple access (FM/CDMA) cellular telephone implementation, the variable attenuator circuit decreases IM distortion by variably attenuating received radio frequency (RF) signals before an initial RF amplification stage to reduce the level of undesirable frequency mixing products. The variable attenuator circuit is turned on (activated) and off (deactivated) at a single, relatively low, input power level. An attenuator enable signal is also supplied from a logic unit of the mobile station to enable operation of the variable attenuator circuit throughout operation in a digital mode. Thus, while enabled, as soon as the input signal power level rises above a defined activation threshold amount, the variable attenuator circuit is activated and begins attenuating the input signal responsive to input signal power levels based upon a received signal strength indication output from a separate automatic gain control circuit. After the attenuation begins gradually, thus avoiding excessive …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.