On-demand receive filtering in an UMTS terminal

Abstract

This paper describes a novel on-demand receive filter in an UMTS terminal. The receive filter is the first function after the Analog-to-Digital converter and is for that reason one of the most computation intensive parts in a receiver. The proposed filter architecture measures the out-of-band interference and calculates the required attenuation, which is used to select the appropriate filter. To assess the advantages of this on-demand receive filter, we have carried out field strength measurements in the UMTS FDD downlink band (2.1 GHz). These measurements were carried out in Amsterdam, a dense urban area with 5 active UMTS operators. Our measurement results show that in a live network configuration there is almost no out-of-band interference. Moreover, an on-demand filter would save in this case more than 68% power compared to a fixed conventional receive filter.