Andreas Pascht

900 MHz pulse-width-modulated class-s power amplifier with improved linearity

The following paper presents a novel 900MHz pulse-width-modulated current-mode class-S power amplifier. The conversion from an analog to a digital signal, which can be handled by the subsequent switch-mode-stage, is implemented using a fast pulse-width-modulator. The complete class-S amplifier is characterized using clipped WCDMA signals with 5MHz and 80MHz bandwidth, respectively. For the 5MHz signal, the measured spectrum at the amplifiers output shows good EVM of < 12% (approx. 1.5% degradation assumed for class-S PA) and also meets the 3GPP ACLR requirements within 9dB input power range. The capability to support large signal bandwidths is demonstrated, using an 80MHz WCDMA signal, thus meeting the expectations on class-S amplifier for the first time with respect to signal bandwidth.

Estimation and compensation of IQ-imbalances in direct down

A new method for the estimation and the compensation of IQ-imbalances in direct conversion receivers is presented. The considerations are based on a multi carrier receiver structure for universal mobile telecommunications systems (UMTS) base stations with a required image suppression of at least 60 dB. Therefore an error compensation in the digital domain is necessary. In laboratory measurements using a W-CDMA signal, the image suppression could be improved by 50.3 dB to a resulting value of 75.1 dB.