Design of CIC roll-off compensation filter in a W-CDMA digital IF receiver

Abstract

In a digital intermediate frequency (IF) receiver, decimation is performed to reduce the computational complexity and cascaded integrated comb (CIC) filter is used together with the decimation as an anti-aliasing filter. However, the CIC filter generates the roll-off phenomenon in the pass-band, which causes the receiving performance to be considerably degraded due to the distorted pass-band flatness of the receiving filter. In this paper, we propose a design method of the CIC roll-off compensation filter to reduce the performance degradation due to the roll-off characteristics of the CIC filter for a W-CDMA digital IF receiver. The performance of the proposed CIC roll-off compensation filter is confirmed through computer simulation in such a way that bit error rate (BER) is minimized by compensating the roll-off characteristics. In addition, the proposed method can be used in the design of a digital-to-analog (DAC) compensation filter and interpolator in the transmitter.