Thomas Bitzer

Realisation of a SiGe-HBT direct down conversion receiver for UMTS base stations

In this work, the realisation of a direct down conversion receiver for the application in UMTS base stations is presented The analogue receiver functionality is completely integrated, based on a SiGe-HBT process with a transit frequency f/sub T/=50 GHz and a minimum noise figure F/sub min/=1 dB. It is designed to convert four neighbouring W-CDMA frequency channels of 3.84 MHz bandwidth simultaneously to the base band. The final carrier separation is done after the AD-conversion in the digital domain. Due to the requirements concerning image suppression, a low IQ imbalance in the analogue receiver part and an error compensation in the digital domain are essential. The receiver features a noise figure NF<2 dB and a power amplification in the range of 38 to 40 dB.

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.