A new technique for designing digitally tuned frequency selective analogue
integrated circuits is proposed. The technique incorporates the R-2R ladder
as a circuit element into the circuit design to provide precise frequency
characteristics that can be tuned over a wide range. Two filters are descri
bed to illustrate the proposed approach. The proposed filters are used to i
mplement the channel-select filter of a multi-standard direct conversion wi
reless receiver and the bandpass filter of a low IF frequency-hopping recei
ver.