Design and FPGA implementation of multiplierless comb filter Richa Barsainya, Meenakshi Agarwal* ,† and Tarun Kumar Rawat Division of ECE, Netaji Subhas Institute of Technology, New Delhi, India SUMMARY The main objective of this paper is to design and implement minimum multiplier, low latency structures of a comb filter. Multipliers are the most area and power consuming elements; therefore, it is desirable to realize a filter with minimum number of multipliers. In this paper, design of comb filters based on lattice wave dig- ital filters (LWDF) structure is proposed to minimize the number of multipliers. The fundamental processing unit employed in LWDF requires only one multiplier. These lattice wave digital comb filters (LWDCFs) are realized using Richards’ and transformed first-order and second-order all-pass sections. The resulting struc- tural realizations of LWDCFs exhibit properties such as low coefficient sensitivity, high dynamic range, high overflow level, and low round-off noise. Multiplier coefficients of the proposed structures are imple- mented with canonic signed digit code (CSDC) technique using shift and add operations leading to multiplierless implementation. This contributes in reduction of number of addition levels which reduces the latency of the critical loop. A field programmable gate array (FPGA) platform is used for evaluation and testing of the proposed LWDCFs to acquire advantages of the parallelism, low cost, and low power con- sumption. The implementation of the proposed LWDCFs is accomplished on Xilinx Spartan-6 and Virtex-6 FPGA devices. By means of examples, it is shown that the implementations of the proposed LWDCFs attain high maximum sampling frequency, reduced hardware, and low power dissipation compared with the existing comb filter structures. Copyright © 2017 John Wiley & Sons, Ltd. Received 22 July 2016; Accepted 30 December 2016 KEY WORDS: digital signal processing; comb filter; field programmable gate array; Lattice wave digital filter; canonic signed digit code 1. INTRODUCTION A filter that has multiple pass-bands and stop-bands is known as comb filter. It notches out harmonic interferences while leaving the broadband signal unchanged. A comb filter has a frequency response that is a periodic function of ω with a period 2π L , where L is the positive integer. Comb filter finds application in the areas of communication, control and biomedical engineering to remove power line disturbances, and for the restoration of audio signals badly corrupted by periodic signals [1–5]. A comb filter is mainly designed by replacing z with z L in a transfer function H (z) of a filter having a single pass-band and/or stop-band. A comb filter can be generated from either a FIR or an infinite impulse response (IIR) filter [3,6,7]. For linear phase applications, FIR filters are preferred but their efficient design requires higher number of coefficients compared with its IIR counterparts for the same specifications. This results in increased computation complexity of FIR filters [8]. A comb filter designed using FIR systems has a design constraint that the notches have the relatively large bandwidth leading to attenuation of other frequency components around the desired nulls. Whereas, IIR comb filters provide much sharper notch band and require smaller number of arithmetic *Correspondence to: Meenakshi Agarwal, Room no: 135, ECE Division, Netaji Subhas Institute of Technology, Sector- 3, Dwarka, New Delhi 110075, India. † E-mail: mishaagg@gmail.com Copyright © 2017 John Wiley & Sons, Ltd. INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS Int. J. Circ. Theor. Appl. (2017) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/cta.2324