On the Polyphase Decomposition for Design of Generalized Comb Decimation Filters

Generalized comb filters (GCFs) are efficient anti-aliasing decimation filters with improved selectivity and quantization noise (QN) rejection performance around the so called folding bands with respect to classical comb filters. In this paper, we address the design of GCF filters by proposing an efficient partial polyphase architecture with the aim to reduce the data rate as much as possible after the Sigma-Delta A/D conversion. We propose a mathematical framework in order to completely characterize the dependence of the frequency response of GCFs on the quantization of the multipliers embedded in the proposed filter architecture. This analysis paves the way to the design of multiplier-less decimation architectures. We also derive the impulse response of a sample 3rd order GCF filter used as a reference scheme throughout the paper.Comment: Submitted to IEEE TCAS-I, February 2007; 11 double-column pages, 9 figures, 1 tabl

Design of Multistage Decimation Filters Using Cyclotomic Polynomials: Optimization and Design Issues

This paper focuses on the design of multiplier-less decimation filters suitable for oversampled digital signals. The aim is twofold. On one hand, it proposes an optimization framework for the design of constituent decimation filters in a general multistage decimation architecture. The basic building blocks embedded in the proposed filters belong, for a simple reason, to the class of cyclotomic polynomials (CPs): the first 104 CPs have a z-transfer function whose coefficients are simply {-1,0,+1}. On the other hand, the paper provides a bunch of useful techniques, most of which stemming from some key properties of CPs, for designing the proposed filters in a variety of architectures. Both recursive and non-recursive architectures are discussed by focusing on a specific decimation filter obtained as a result of the optimization algorithm. Design guidelines are provided with the aim to simplify the design of the constituent decimation filters in the multistage chain.Comment: Submitted to CAS-I, July 07; 11 pages, 5 figures, 3 table

Design, analysis and evaluation of sigma-delta based beamformers for medical ultrasound imaging applications

The inherent analogue nature of medical ultrasound signals in conjunction with the abundant merits provided by digital image acquisition, together with the increasing use of relatively simple front-end circuitries, have created considerable demand for single-bit beamformers in digital ultrasound imaging systems. Furthermore, the increasing need to design lightweight ultrasound systems with low power consumption and low noise, provide ample justification for development and innovation in the use of single-bit beamformers in ultrasound imaging systems. The overall aim of this research program is to investigate, establish, develop and confirm through a combination of theoretical analysis and detailed simulations, that utilize raw phantom data sets, suitable techniques for the design of simple-to-implement hardware efficient digital ultrasound beamformers to address the requirements for 3D scanners with large channel counts, as well as portable and lightweight ultrasound scanners for point-of-care applications and intravascular imaging systems. In addition, the stability boundaries of higher-order High-Pass (HP) and Band-Pass (BP) Σ−Δ modulators for single- and dual- sinusoidal inputs are determined using quasi-linear modeling together with the describing-function method, to more accurately model the modulator quantizer. The theoretical results are shown to be in good agreement with the simulation results for a variety of input amplitudes, bandwidths, and modulator orders. The proposed mathematical models of the quantizer will immensely help speed up the design of higher order HP and BP Σ−Δ modulators to be applicable for digital ultrasound beamformers. Finally, a user friendly design and performance evaluation tool for LP, BP and HP modulators is developed. This toolbox, which uses various design methodologies and covers an assortment of modulators topologies, is intended to accelerate the design process and evaluation of modulators. This design tool is further developed to enable the design, analysis and evaluation of beamformer structures including the noise analyses of the final B-scan images. Thus, this tool will allow researchers and practitioners to design and verify different reconstruction filters and analyze the results directly on the B-scan ultrasound images thereby saving considerable time and effort

Efficient Design and Synthesis of Decimation Filters for Wideband Delta-Sigma ADCs

A design methodology for synthesizing power-optimized decimation filters for wideband Delta Sigma (ΔΣ) analog-to-digital converters (ADCs) for next-generation wireless standards is presented. The decimation filter is designed to filter the out-of-band quantization noise from a fifth-order continuous-time ΔΣ modulator, with 20 MHz signal bandwidth and 14-bits resolution. The modulator employs an oversampling ratio (OSR) of 16 with a clock rate of 640 MHz. Retiming, pipelining, Canonical Signed Digits (CSD) encoding has been utilized along with an optimized halfband filter to realize the power savings in the overall decimation filter. A process flow to rapidly design the optimized filters in MATLAB, generate the hardware description language (HDL) code and then automatically synthesize the design using standard cells has been presented. The decimation filter is implemented using standard cells in a 45 nm CMOS technology occupies a layout area of 0.12 mm2 and consumes 8 mW power from the 1.1 V supply

Sharpening of the multistage modified comb filters

This paper describes the application of filter sharpening method to the modified comb filter (MCF) in the case of decimation factor, which is product of two or more positive integers. It is shown that in the case of multistage decimation with MCF, filters in each stage are also MCF. Applying the sharpening to the decimation filter in the last stage provides very good results, with savings in the number of operations comparing to the case of sharpening of the complete filter. Direct-form FIR polyphase filter structure is proposed for the filters in each stage