Nth order cascade integrated comb filter take n moving average filters in sequence with decimation at the end rearrange all integrators first, and comb filters. The cic filter is used as an anti aliasing filter, when the data rate is high since the operation in the cic filter only consists of addition operation. An improved wideband cic filter design of software radio. In this tutorial, matthew donadio provides continued. This paper presents multiplierless cic compensator for software defined radio sdr application. Scopefir can design cic filters, which are widely used in hardwarebased multirate applications.
Scopefir can design filters, hilbert transformers, or differentiators. The overall system response is plotted for you to verify key system specifications such as the passband ripple and stopband attenuation. Analysis and implementation of multirate cascaded integrator. Here is an example of frequency magnitude response of a 1storder, d8, decimation filter. If a unitimpulsesequence, a unityvalued sample followed by many zerovalued samples, was applied to the comb stage, that stages output is. Because of the popularity of this structure many authors also call the comb filter as cic filter. In the cic filter design, the passband response and stopband rejection characteristics are managed by threeinteger parameters, which are number of stages, the differential delay and the number of bits in inputoutput registers. The proposed multiplierless linear phase finite impulse response compensator works at a. A simple design for wideband compensation of a cascadedintegratorcomb cic decimation filter is presented. The script uses the frequency sampling method to design a fir filter that has an inverse sinc frequency response.
To overcome the magnitude droop, a fir filter that has a magnitude response that is the inverse of the cic filter can be applied to achieve frequency response correction. Using cic decimation filter with multichannel support intel. Designing digital down conversion systemsusing cic and fir filters. Cic interpolation filter with multichannel data support for stratix v. One efficient implementation of this filter is called cic cascadedintegratorcomb filter proposed by hogenauer hogenauer, 1981. Sample rate conversion filter design for multistandard. Cic filters are very useful in applications where one needs. When you design either a decimator or interpolator, the resulting filter is a cic filter that decimates or interpolates your input signal. It is combination of five stage integrator and comb stages. Cic filter cascaded integratorcomb cic filters, also known as hogenauer filters, are used to achieve arbitrary and large sample rate changes in digital systems. Overflow of integrator in cic filter there are many solution.
Designing digital down conversion systems using cic and. Design cascaded integratorcomb cic filter simulink. Differential delay specify the differential delay of your cic filter as an integer value greater than or equal to 1. Hz1r 1zr1z1 n where, r and n are the decimation rate and order of the cic filter. The word lengths of the filter stages must be no increasing. The use of this design is governed by, and subject to, the terms and conditions of the hardware reference design license agreement. The transfer function of the cic filter can be written as. The clock divider circuit is introduced between the integrator and comb filter. The second subplot shows that the fir filter and cic filter provide nearly identical interpolation, when the correction gain equals the gain of the last section of the cic filter. Using cic decimation filter with multichannel support. Understanding cascaded integratorcomb filters cic and.
The inputoutput word length and fraction length are specified. Pdf cic filter for sample rate conversion in software defined. Hogenauer filter cascade integrator comb filters informit. The cic interpolation filter increases the sampling rate by 32. Pdf software defined radio sdr or software radio is one of the most. Hardware efficient fir compensation filter for delta sigma modulator analog to digital converters. Therefore, cic is a suitable and economical filter architecture for hardware implementation, and is widely used in sample rate conversion designs such as digital down converters ddc and digital up converters duc. Design of cic filters for software radio system ieee conference. The cic filter is used in both up sampling and down sampling applications. Cic compensator filter specification object matlab fdesign.
Cic filter design the antialiasing filter is the important role of decimation filter and also used to find out the less number of decimation stages that could provide useful implementation about cic filter. Reducing power consumption in cic filter algorithm designs september 4, 2012 embedded staff a major design goal for cascaded integratorcomb cic filters, especially in conjunction with sample rate conversion, is to minimize their hardware power consumption by reducing data word width and reducing data clock rates wherever possible. Digital filter designers like to see zplane polezero plots, so we provide the zplane characteristics of a d 5 cic filter in figure 4c, where the comb filter produces d zeros, equally spaced around the unitcircle, and the integrator produces a single pole canceling the zero at z 1. Cascaded integratorcomb cic filter introduction dspguru. The ad6620 filter design software requires windows 95 or later 32bit operating. The accumulator must have 17 or more bits to implement the 100tap boxcar filter as a cic filter. To show how the cic decimation filter is constructed, the following figure presents a block diagram of the filter structure for a twosection cic decimation filter n 2. The most simple decimation filter is comb filter which does not require multipliers.
The compensator is composed of two simple filters with sinewave form of magnitude responses. Onchip implementation of cascaded integrated comb filters. The parameters of the design are the sinewave amplitudes expressed as powersoftwo and estimated in a way to. Singlestage cic filter timedomain responses when d 5 view fullsized image. Cic lters are much used in applications where one needs to change the sampling frequency in a big ratio, for instance for decimation reduction of the sampling rate. Binary integers and overflow cascade integrator comb. Previous efforts have focused on enhancing the performance of these filters by either improving their passband response 19,20 or stopband rejection capabilities 21. Design of five stage cic decimation filter for signal. What is the benefits of a cic decimator compared to directly downsampling by 4 and. Joint cic compensation and interpolation filter design as mentioned in section 2, cic filters are an integral part of most digital decimation filter designs in software radios.
If the filter is applied to an upsampling task, the comb filter is placed at the input to the cic filter. Simulation and design of cic filter using verilog hdl intel. However, a cic filter followed by a short to moderate length fir or iir proves highly applicable. These filters are used as decimation or interpolation filters and can be efficiently implemented without multipliers, utilizing only adders and subtractors. The initial model was designed and tested in simulink, a. This block brings the filter design capabilities of the filterbuilder function to the simulink environment. The proposed system is to design the basic concept of the five stage cic decimation filter. Cascaded integratorcomb cic filter lattice semiconductor. Sep 04, 2012 reducing power consumption in cic filter algorithm designs september 4, 2012 embedded staff a major design goal for cascaded integratorcomb cic filters, especially in conjunction with sample rate conversion, is to minimize their hardware power consumption by reducing data word width and reducing data clock rates wherever possible. The number of bits of the first filter stage must be greater than or equal to the quantity bmax. Request pdf design of cic filters for software radio system cascaded integrator comb cic filters are used to realize computationally efficient decimation, interpolation or sample rate. Magnitude response of a 1storder, d 8, decimating cic filter. Some applications that use the cic filter include software designed radios.
Scopefir lets you import filters which have been designed with another application so you can analyze them using scopefirs powerful plotting and analysis capabilities, and to modify them using scopefirs powerful filter modification capabilities. A matlab script designing cic compensating filter is provided for your reference. Cascaded integratorcomb cic filter cascaded integratorcomb cic filters, also known as hogenauer filters, are used to achieve arbitrary and large sample rate changes in digital systems. Implementation of optimized cascaded integrator comb filters. Moreover, given these specifications, by increasing the filter order, it is possible to obtain designs that more closely approximate an ideal filter. The cic decimation filter with multichannel data support design example demonstrates how to use alteras cascaded integratorcomb cic filter megacore function to implement digital sample rate down conversion for multiple independent data sources.
See the design and comments section for more information. The script uses the frequency sampling method to design a fir filter that has an. Scopefir can design lowpass fir filters having a maximally flat passband. Design cascaded integratorcomb cic filter simulink mathworks. I gotta wrap my head around to design cic compensation filter. Department of electronics, walchand institute of technology, solapur. Pdf design and implementation of efficient cic filter structure for. Reducing power consumption in cic filter algorithm designs. Multiplierless wideband and narrowband cic compensator for. Cic filters electrical engineering at new mexico tech. In the classic paper, an economical class of digital filters for decimation and interpolation, hogenauer introduced an important class of digital filters called cascaded integratorcomb, or cic for short also sometimes called hogenauer filters.
In this syntax, the filter has two sections and the differential delay is 1. The second fir interpolation filter is a compensation fir filter that increases the sampling rate by 2 and compensates for the distortion of the following cic filter. The name of the core component to be instan tiated. Cic filter is equivalent to a number of rectangular windows cascaded recursive filter form, and therefore has a more significant performance limitations. Design multiband complex fir filters of the following types. If not already done, install scilab free numerical computing software. The cic filter frequency response does not have a wide, flat pass band. If n is the number of integrator and comb sections of the cic filter, then 2 n is the last section of the cic filter. A basic knowledge of dsp and digital filter design will help you understand the tradeoff between vari ous cic compensation filter design methods. With typical filter design software packages the user enters numerical values for the desired filters parameters such as cutoff frequency, stopband attenuation, etc.
With typical filter design software packages the user enters numerical values for the desired filter s parameters such as cutoff frequency, stopband attenuation, etc. This means that the cic filters frequency magnitude response is approximately equal to a sinc function centered at 0 hz. For example, if a q 3stage cic decimation filter accepts onebit binary input words from a sigmadelta ad converter and the decimation factor is d 64, binary overflow errors are avoided if the three integrator and. Using matlab program, the efficient five stage cic decimation filter is established. The shape of the filter response provides even fewer degrees of design freedom. Cic interpolation filter with multichannel data support for. The parameters of the design are the sinewave amplitudes expressed as powersoftwo and estimated in. Cascade integratorcomb cic filter this module is an fixedpoint implementation of cic filter with configurable parameters. Design of cic filters for software radio system request pdf. Understanding cic compensation filters prerequisites this document targets digital signal processing dsp systems engineers who must design cic compensation filters for rate conversion systems. This scilab minitoolbox enables you to evaluate in terms of frequency response cic filters, to design what is called a compensation filter, and to simulate the cic filtering on real signals. For this reason, many realworld filtering requirements cannot be met by a cic filter alone. Cic filter constraints cic decimator filter have the following two constraints.
An astounding digital filter design application rick lyons. This paper presents multiplierless cic compensator for softwaredefined radio sdr application. To see why the cic filter is of interest, first we examine its timedomain behavior, for d 5, shown in figure 3. Scopefir is the premiere software tool for finite impulse response fir filter design. The cic contains two subfilters, the comb and the integrator, which can be applied in either order. Filter the signal with a fir filter and coefficients 1 5 10 10 5 1. The cic filter block diagram is shown in figure 2 figure 2. Cascaded integrator comb cic filters are used to realize computationally efficient decimation. The design parameters for the filter are the frequency at which the peak or notch is desired, and either the 3db bandwidth or the filter s qfactor. The name must begin with a letter and be composed of the following characters. Its simple filter specification editor allows you to easily design simple.
Bit width is addressed in more detail in a later section. The script uses the frequency sampling method to design a fir filter that has. Designing digital down conversion systems using cic and fir. For instance, with 10bit input data and a 100tap boxcar filter with a gain of 100, we require 7bits of growth for a bit field width of 17bits. The cic core supports both interpolator and decima tor types.
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