Imbalance-compensated direct down conversion receiver for UMTS base stations

In this work, a new method for the estimation and the compensation of in-phase quadrature-imbalances in direct down conversion receivers is presented. The considerations are based on a receiver structure that is developed for the simultaneous down conversion of up to four neighboring carriers in universal mobile telecommunications system base stations. The image suppression of the system must achieve at least 60 dB. This requirement is not fulfilled by the analogue part and hence, an error estimation and compensation in the digital domain is necessary. In laboratory measurements using a wideband code-division multiple-access signal, the image suppression of the complete set-up including the analogue parts could be improved by 34 dB.