Shaping noise in power amplifiers of duplex communication systems
Patent type: Priority Patent Application
Patent number: US20060217082A
Registration date: March 22, 2005
Abstract
The present invention provides a method and an apparatus for reducing radio frequency noise within a duplex communication system. The method comprises sensing a radio frequency transmit signal capable of operating a power amplifier that is capable of operation at a microwave transmit frequency and using a filter to cause an asymmetric notch in a noise power density spectrum in a radio frequency output signal to shape the noise power density spectrum at a low radio frequency power level in the microwave transmit frequency in response to the radio frequency transmit signal. In a base station, a duplex filter arrangement may trim the wideband noise within a power amplifier, such as a Class-S power amplifier. An increased filtering effort may be spend at a low power level at a power amplifier input. A desired noise shaping may be applied in the power amplifier to prevent desensitization of a receiver of a base station by the wideband noise at one or more receive frequencies for a digital cellular network in a telecommunication system. Use of a noise shaping filter with an asymmetric shape response may attenuate noise on a lower side of a transmit frequency and increase the noise on a higher side of the transmit frequency. A shift of the noise power to desired frequency regions, enables the base station to tolerate relatively more noise at higher frequencies than in a receive band, at frequencies that are lower than a transmit band. As a result, a Class-S power amplifier may provide both high linearity and efficiency.
Invention
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