A Low Sampling Frequency Switched Capacitor Low-pass Filter for Wireless Receivers

J. Kopanski, Ł. Wiechowski, K. Siwiec, W. Pleskacz (Warsaw Univ. of Techn., Poland)

This paper presents a low-pass filter with variable gain for use in direct conversion wireless receivers. The filter is implemented using the switched-capacitor technique. Its sampling clock frequency is, however, only moderately higher than signal frequencies of interest. To cope with the problems that this creates, a new set of design equations are derived, from analytically calculated filter transfer function in Z domain. Circuit implementation is shown and its electrical simulation results, both schematic and post-layout are presented.