International Journal of Scientific & Engineering Research, Volume 6, Issue 8, August-2015 1744 ISSN 2229-5518 IJSER © 2015 http://www.ijser.org Polyphase CIC Filter Structures for Digital Receivers R.Latha , Dr.P.T.Vanathi Abstract-There are multiple ways to implement a decimator filter. In this paper, first approach addresses usage of Cascaded Integrator Comb (CIC) filter transfer function through the polynomial formula with zeros and poles. Second approach is to implement a conventional poly-phase comb filter and the third approach is based on modified poly-phase comb filter. A Power efficient poly-phase decomposition comb filter with a clock distribution algorithm for its memory elements is presented. The proposed algorithm results in a significant reduction in the dynamic power consumption, comparing with the conventional poly-phase decomposition comb filter that is widely used as a first stage of decimation process in sample rate conversion for multi-rate telecommunication receivers. A general form of the proposed clock distribution algorithm is presented with respect to the decimation factor of the poly-phase comb filter. It is shown that, using the proposed clock distribution algorithm reduces the dynamic power consumption of the memory elements for a second order poly-phase comb filter when compared with polynomial CIC filter. As well as, we can reduce the dynamic power consumption of the memory elements for a third order poly-phase comb filter. It is estimated such that power consumed in modified poly-phase comb decimation filter is less than the power consumed in conventional poly-phase comb decimation filter. Index Terms– Polynomial, CIC,Comb filter, Low power, Clock Distribution, Poly-phase Decomposition, Decimation filter. ——————————  —————————— 1 INTRODUCTION Decimation filter has wide application in both the analog and digital system for data rate conversion as well as filtering [1]. The decimating low-pass filter accepts input samples from the mixer output at the full Analog to Digital (A/D) sampling frequency f s . It utilizes digital signal processing to implement a Finite Impulse Response (FIR) filter transfer function [2]. The filter passes all signals from 0 Hz up to a programmable cutoff frequency or bandwidth, and rejects all signals above that cutoff frequency. This digital filter is a complex filter, which processes both I and Q signals from the mixer. At the output, one can select either I and Q (complex) values or just real values, depending on your system requirements. In multi-rate receivers, decimation filters are required to perform channel select filtering and Sample Rate Conversion (SRC) to the base-band of the selected channel. Reducing the power consumption of the decimation filter is considered as one of the most important goals, since it operates at a high sampling frequency. That is why multiplier free Cascaded Integrator Comb Filter (CIC) is widely used in multi-rate receiver designs [3] . However, since the integrator part of the CIC decimation filter still works at the higher input sampling frequency, its power consumption is still high. Recently, lower power consumption has been achieved using the FIR filter and the Poly-FIR filter. 2 POLYNOMIAL CIC FILTER Fig.1 shows the block diagram of the polynomial CIC filter. The output for each time sample is determined by the current input, previous input, and previous output. In order to realize this design, registers are used to store the previous input sample and output sample. Fig.2 shows the digital circuit to implement the polynomial CIC filter. Each of the multiplication is implemented using a CSD multiplier where each multiplier is implemented using shift register and adder. ———————————————— • R.Latha is currently doing Ph.D degree programme in Information and Communication Engineering in Anna University, Chennai, India, PH- 07829198800. E-mail: lathar_26@rediffmail.com • DrP.T.Vanathi is currently working as an Associate Professor in Electronics & Communication Engineering at PSG College of Technology , Coimbatore, India, PH-09486438516. E-mail: ptvani@yahoo.com IJSER