Methods for Improving Alias Rejections in Comb Filters

2018 ◽  
pp. 4746-4760
Author(s):  
Gordana Jovanovic Dolecek
Keyword(s):  
Chebyshev Polynomials ◽  
Sampling Rate ◽  
Comb Filter ◽  
Comb Filters ◽  
Decimation Filter

Downsampling is the process of decreasing the sampling rate of signal by an integer. This process may introduce the unwanted spectrum replica called aliasing. To avoid aliasing the signal must be filtered by decimation filter prior downsampling. Decimation consists of filtering and downsampling. The most simple decimation filter is comb filter usually used in the first stage of decimation. However, comb filter does not provide a good aliasing rejection. This paper presents the methods for improving alias rejection of comb filters. The methods are based on comb zero rotation, cosine filters, Chebyshev polynomials, and cascade of combs with different parameters.

Methods for Improving Alias Rejections in Comb Filters

2019 ◽  
pp. 891-909
Author(s):  
Gordana Jovanovic Dolecek
Keyword(s):  
Chebyshev Polynomials ◽  
Sampling Rate ◽  
Comb Filter ◽  
Comb Filters ◽  
Decimation Filter

Downsampling is the process of decreasing the sampling rate of signal by an integer. This process may introduce the unwanted spectrum replica called aliasing. To avoid aliasing, the signal must be filtered by decimation filter prior to downsampling. Decimation consists of filtering and downsampling. The simplest decimation filter is comb filter usually used in the first stage of decimation. However, comb filter does not provide a good aliasing rejection. This chapter presents methods for improving alias rejection of comb filters. The methods are based on comb zero rotation, cosine filters, Chebyshev polynomials, and cascade of combs with different parameters.

scholarly journals Sharpening of the multistage modified comb filters

2011 ◽  
Vol 8 (3) ◽  
pp. 281-291 ◽  
Author(s):  
Marko Nikolic ◽  
Miroslav Lutovac
Keyword(s):  
Comb Filter ◽  
Polyphase Filter ◽  
Filter Structure ◽  
Direct Form ◽  
Comb Filters ◽  
Decimation Filter ◽  
Last Stage ◽  
Positive Integers

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.

Comb-Based Filters for Sampling Rate Conversion

2009 ◽  
pp. 316-346
Author(s):  
Ljiljana Milic
Keyword(s):  
Communication Systems ◽  
Moving Average ◽  
Sampling Rate ◽  
Software Radio ◽  
Satellite Communications ◽  
Comb Filter ◽  
Single Chip ◽  
Comb Filters ◽  
The Individual ◽  
Rate Conversion

Comb filters are developed from the structures based on the moving average (boxcar) filter. The combbased filter has unity-valued coefficients and, therefore, can be implemented without multipliers. This filter class can operate at high frequencies and is suitable for a single-chip VLSI implementation. The main applications are in communication systems such as software radio and satellite communications. In this chapter, we introduce first the concept of the basic comb filter and discuss its properties. Then, we present the structures of the comb-based decimators and interpolators, discuss the corresponding frequency responses, and demonstrate the overall two-stage decimator constructed as the cascade of a comb decimator and an FIR decimator. In the next section, we expose the application of the polyphase implementation structure, which is aimed to reduce the power dissipation. We consider techniques for sharpening the original comb filter magnitude response and emphasize an approach that modifies the filter transfer function in a manner to provide a sharpened filter operating at the lowest possible sampling rate. Finally, we give a brief presentation of the modified comb filter based on the zero-rotation approach. Chapter concludes with several MATLAB Exercises for the individual study. The reference list at the end of the chapter includes the topics of interest for further research.

Design and Research of Digital Decimation Filter Based on FPGA

2011 ◽  
Vol 105-107 ◽  
pp. 2086-2091
Author(s):  
Yao Li
Keyword(s):  
High Speed ◽  
Sampling Rate ◽  
Comb Filter ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Low Pass ◽  
Cic Filter ◽  
Decimation Filter ◽  
Fpga Chip ◽  
Digital Down Conversion

This paper studies and analyses various digital filter and decimation structure. On this basis, by using QUARTUS development system design the decimation device modules, through the waveform simulation validated its correctness. Finally,a program is written into FPGA chip by the hardware platform. In the digital down conversion (DDC), CIC (cascade integral comb) filter plays an important role. It is mainly used for sampling rate, as well as low-pass filter effect. The main characteristics of CIC filter, using only adders, subtractor and register (no multiplier), so fewer resources occupied, implementation is simple and high speed. Based on the analysis of the principle of CIC filter,simulate and synthesize based on the theory of using VHDL language in FPGA. And successful application in the development of DDC chip. Keyword: CIC (cascade integral comb) filter,FPGA,VHDL

Methods for Simultaneous Improvement of Comb Pass Band and Folding Bands

2018 ◽  
pp. 6171-6183
Author(s):  
Gordana Jovanovic Dolecek
Keyword(s):  
Design Methods ◽  
Comb Filter ◽  
Signal Spectrum ◽  
Pass Band ◽  
Original Spectrum ◽  
Compensator Design ◽  
Decimation Filter

This decimation introduces the replicas of the main signal spectrum. If the signal is not properly filtered, the overlapping of the repeated replicas of the original spectrum, called aliasing, may occur. The aliasing may destroy the useful information of the decimated signal and must be eliminated by the filter which precedes the decimation, called decimation filter. The most popular decimation filter is a comb filter, usually used in the first stage of decimation. However its magnitude characteristic is not flat in the pass band of interest and there is not enough attenuation in the folding bands. Different methods are proposed to improve comb magnitude characteristic. This article presents an overview of methods for simultaneous improvement of comb magnitude characteristic in both: pass band and folding bands. The methods are divided into three main groups: Sharpening-based methods, Corrector–based methods, and Methods based on the combination of alias rejection and compensator design methods.

Comb Filters Characteristics and Current Applications

2018 ◽  
pp. 6007-6018
Author(s):  
Miriam Guadalupe Cruz-Jimenez ◽  
David Ernesto Troncoso Romero ◽  
Gordana Jovanovic Dolecek
Keyword(s):  
Comb Filter ◽  
Digital Audio ◽  
Linear Phase ◽  
Phase Filter ◽  
Comb Filters ◽  
Passband Droop

The comb filter is a very popular linear-phase filter due its simplicity, i.e. all its coefficients are equal to unity. As a consequence, it does not require multipliers or coefficients storage. This characteristic makes this filter attractive for many applications, as for example, in decimation, communications, digital audio, among others. However, the comb filter presents passband droop and a poor attenuation in the stopband region. In this proposal, the comb filter characteristics are reviewed and illustrated with one example. Additionally, the selected methods commonly used to improve the magnitude characteristics of a comb filter will be described and illustrated with examples.

Design of Sampled Fiber Bragg Grating Comb Filter

2013 ◽  
Vol 397-400 ◽  
pp. 1850-1853
Author(s):  
Dan Dan Zhu ◽  
Jian Song ◽  
Xiu Zhen Hu ◽  
Yuan Yuan Zhang
Keyword(s):  
Theoretical Basis ◽  
Preparation Method ◽  
Sampling Rate ◽  
Optical Fiber Communication ◽  
Grating Period ◽  
Comb Filter ◽  
Duty Ratio ◽  
Fiber Grating ◽  
Fiber Communication ◽  
Sampled Fiber Bragg Grating

This article based on the theoretical basis of sampled fiber grating, using transfer matrix method to analyse sampled fiber grating, and the analysed the spectrum of sampled fiber grating, and studied sampled fiber grating filter properties. by adjusting the parameters of sampling grating such as: the length of the grating, grating period, duty ratio ( sampling rate) and other parameters, to construct 6 comb filter, and finally come to sampled fiber grating filter preparation method and process in the theory, analysed the application of sampled fiber grating filter in some optical fiber communication fields.

scholarly journals A VLSI DSP DESIGN AND IMPLEMENTATION OF COMB FILTER USING UN-FOLDING METHODOLOGY

2012 ◽  
pp. 72-77
Author(s):  
PURU GUPTA ◽  
TARUN KUMAR RAWAT
Keyword(s):  
Signal Processing ◽  
Computation Time ◽  
Digital Signal ◽  
Vlsi Circuits ◽  
Comb Filter ◽  
Destructive Interference ◽  
Sample Period ◽  
Iteration Bound ◽  
Comb Filters ◽  
Digital Waveguide

In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. Comb filters are used in a variety of signal processing applications that is Cascaded Integrator-Comb filters, Audio effects, including echo, flanging, and digital waveguide synthesis and various other applications. Comb filter when implemented has lower through-put as the sample period can not be achieved equal to the iteration bound because node computation time of comb filter is larger than the iteration bound. Hence throughput remains less. This paper present the comb filter using one of the methodology needed to design custom or semi custom VLSI circuits named as Un-Folding which increases the throughput of the comb filter. Un-Folding is a transformation technique that can be applied to a DSP program to create a new program describing more than one iteration of the original program. It can unravel hidden con-currency in digital signal processing systems described by DFGs. Therefore, unfolding has been used for the sample period reduction of the comb filter for its higher throughput.

scholarly journals Sampling Rate Optimization for Improving the Cascaded Integrator Comb Filter Characteristics

2021 ◽  
Vol 38 (1) ◽  
pp. 97-103
Author(s):  
Raouf Amrane ◽  
Youcef Brik ◽  
Samir Zeghlache ◽  
Mohamed Ladjal ◽  
Djamel Chicouche
Keyword(s):  
Signal Processing ◽  
Finite Impulse Response ◽  
Sampling Rate ◽  
Comb Filter ◽  
Existing Structures ◽  
High Sampling Rate ◽  
Cic Filter ◽  
Stopband Attenuation ◽  
Rate Optimization ◽  
Passband Droop

The cascaded integrator comb (CIC) filters are characterized by coefficient less and reduced hardware requirement, which make them an economical finite impulse response (FIR) class in many signal processing applications. They consist of an integrator section working at the high sampling rate and a comb section working at the low sampling rate. However, they don’t have well defined frequency response. To remedy this problem, several structures have been proposed but the performance is still unsatisfactory. Thence, this paper deals with the improvement of the CIC filter characteristics by optimizing its sampling rate. This solution increases the performance characteristics of CIC filters by improving the stopband attenuation and ripple as well as the passband droop. Also, this paper presents a comparison of the proposed method with some other existing structures such as the conventional CIC, the sharpened CIC, and the modified sharpened CIC filters, which has proven the effectiveness of the proposed method.

scholarly journals Modified CIC Filter for Rational Sample Rate Conversion

1970 ◽  
Vol 4 (1) ◽  
pp. 15-20 ◽  
Author(s):  
Gordana Jovanovic Dolecek
Keyword(s):  
Impulse Response ◽  
Software Defined Radio ◽  
Conversion Factor ◽  
Sampling Rate ◽  
Prime Numbers ◽  
Comb Filter ◽  
Triangular Form ◽  
Cic Filter ◽  
Sample Rate ◽  
Rate Conversion

The modification of the conventional CIC (cascadedintegrator-comb) filter for rational sample rate conversion (SRC) in software defined radio (SWR) systems is presented here. The conversion factor is a ratio of two mutually prime numbers, where the decimation factor M can be expressed as a product of two integers. The overall filter realization is based on a stepped triangular form of the CIC impulse response, the corresponding expanded cosine filter, and sine-based compensation filter. This filter performs sampling rate conversion efficiently by using only additions/subtractions making it attractive for software defined radio (SWR) applications.

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