An optimal entropy coding scheme for efficient implementation of pulse shaping FIR filters in digital receivers

The most computationally intensive part of wide-band receivers is the IF processing block. Digital filtering is the main task in IF processing. Infinite precision filters require complicated digital circuits due to coefficient multiplication. This paper presents an efficient method to implement pulse shaping filters for a dual-mode GSM/W-CDMA receiver. We use an arithmetic scheme, known as pseudo floating-point (PFP) representation to encode the filter coefficients. By employing a span reduction technique, we show that the filters can be coded using an optimal entropy scheme employing PFP which requires only considerably fewer bits than conventional 24-bit and 16-bit fixed-point filters. Simulation results show that the magnitude responses of the filters coded in PFP meet the attenuation requirements of GSM/W-CDMA specifications.