Implementation of optimized cascaded integrator comb filters. Cascading sharpened cic and polyphase fir filter for. A cic filter is cascade connection of simple integrator and comb filter stages. Design and implementation of efficient cic filter structure for decimation article pdf available in international journal of computer applications 65. An economical class of digital filters for decimation and interpolation abstract. Cic filters also known as hogenauer filters are computationally efficient for. Cic filters efficiently extract baseband signals from narrowband sources using decimation. In 1981, eugene hogenauer 2 invented a new class of economical digital filter for decimation called a cascaded integrator. Garcia department of electronics and computer technology university of granada, 18071 granada, spain email. But the overflow problem isnt discussed in depth therein. Two easy ways to test multistage cic decimation filters. The most simple decimation filter is comb filter which does not require multipliers. Cic filters are a class of linear phase fir filters consisting of a comb part and an integrator part. The cic filters are most economical for hardware implementation as no multiplier circuits are required.
Cascaded integratorcomb cic filter introduction dspguru. Chapter 1 overview cascaded integratorcomb cic filters, also known as hogenauer filters, are multirate filters often used for implementing large sample rate changes in digital systems. When the x in n input sequence to an sstage cic decimation filter is an all ones sequence, the filter s step response will be s samples, of various amplitudes, followed by a constant sequence of d svalued samples. On the other hand, if the cic is applied to a downsampling task, the comb filter is placed. Because of the popularity of this structure many authors also call the comb filter as cic filter. That is, the system sample rate is much larger than the bandwidth occupied by the. This paper describes decimation process by the focus on high speed implementation of cic filter hogenauer eb 1981. Hz1r 1zr1z1 n where, r and n are the decimation rate and order of the cic filter. The transfer function of the cic filter can be written as. The disadvantage of a cic filter is that its passband is not maximally flat, which is undesirable in many applications 3. There is a rate change switch between the two filter sections.
Example frequency response for n 4, m 1, r 7, and f, i. The system function for the composite cic filter referenced to the high sampling rate, f s is. The name of the core component to be instan tiated. Cic filter downsampling as you use htc desire 626s, youll accumulate data and fill its storage capacity over time. Cic filters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. Cic filters also known as hogenauer filters are computationally efficient for extracting baseband signals from narrowband sources using. Decimate signal using cascaded integratorcomb filter simulink. A class of digital linear phase finite impulse response fir filters for decimation sampling rate decrease and interpolation sampling rate increase are presented.
Multiplierless wideband and narrowband cic compensator. Performance analysis and behaviour of cascaded integrator. Cic filter cascadeintegrator comb hogenauer resampling filter fred harris. Also the design complexity with fir filter can be recovered with the cic filter. Cascaded integratorcomb cic filter introduction 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. Example of cascaded integrator comb filter in matlab. Eric jacobsen gave me the name of hogenauer s employer in silicon valley. An economical class of digital filters for decimation and interpolation. Decimate signal using cascaded integratorcomb filter. Free up phone storage space by uninstalling apps and deleting files you no longer want to keep. Harris, in his multirate book, uses the terms cic and boxcar filter interchangeably. Vlsi implementation of cascaded integrator comb filters for. Singlestage cic filter timedomain responses when d 5 view fullsized image. Here are some tips on how to free up phone storage space.
Below is a block diagram for the cic filter i used. The cic decimation filter structure consists of n sections of cascaded integrators, a rate change factor of r, and n sections of cascaded comb filters. When theres a sample rate change in between, the comb and integrator, then harris calls such a system a hogenauer filter. Yes, an ntap delay line fir boxcar filter and the cic filter with n delays in the comb have the same frequency response. The example is part of a modulator that shapes and up samples in a polyphase filter and then interpolates to a higher output sample rate with a cic filter. Design of five stage cic decimation filter for signal. He claimed this was an economical class of digital filter. An economical class of digital filters for decimation and. Table i passband attenuation for large rate change factors elative bandwidth. However, the disadvantage of a cic filter is that its pass band is not flat, which is undesirable in many applications. Yesterday i called hogenauer at his work and briefly described my definition of bmax question. The paper gives a good introduction to cic filters. For a decimating cic filter, the filter starts with cascading some integrator stages, followed by downsampling, and then some. A cic filter consists of an equal number of stages of ideal integrator followed by comb filters.
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. It has the two basic building blocks of a cic filters are integrator and comb. Magnitude response of compensated cic filter for l2 figure 3. Dick 9 cic filter frequency response frequency response of cic filter is produced by evaluating on the unit circle where f is the frequency wrtthe low sampling rate fsr the power response is h z z k k rm n cic l nm o. The basic concept of cic filter is given in fig, which consists of. Here in the figure we are designing cic decimation filter with the help of simulink software in matlab. Implementation of cic filter for multirate transmission systems. Programming code cic low pass filter, high pass filter, cascaded form cic now using the proposed method coefficients of compensated filter is calculated and frequency response is plotted. Fpga ip implements a cascaded integratorcomb cic filter with data ports that are compatible with the avalon streaming interface. At that time hogenauer worked for a premier signal processing company called esl inc. Hogenauer invented the cic filter structures is economical class of linear phase, fir filter. Design of a novel class of selective cic filter functions based on the classical cic filters, by spreading the delays in the cic filter comb stages, is recently shown in 1618.
Cascaded integratorcomb cic filters, also known as hogenauer filters, are multirate filters often used for implementing large sample rate changes in digital systems. A cic filter also known as a hogenauer filter can be used to. All content in this area was uploaded by eugene hogenauer on jan 06, 2015. Cic filter and pfir filter is used to solve the bandwidth issues in both the sections. Cic cascadedintegratorcomb filter proposed in 4 is widely used as antialiasing and antiimaging filter due to its simplicity. Hogenauer devised a flexible, multiplierfree filter suitable for hardware implementation that can also handle. 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. Because he hadnt thought about cic filters for years we agreed that id put my question in an email that id send to him, which i did later yesterday morning. An economical class of digital filters for decimation and interpolation preceding unsigned comment. The relation of cic to modular arithmetic is discussed in the register growth chapter of an economical class of digital filters for decimation and interpolation by e. Ddc the decimation filter can be done poly phase and cic based ddc can be implemented in wireless communication systems. We now examine an example of the use of the hogenauer resampled cic filter. Expanded view of the multistage cic filter gain response figure 3.
Application of hardware efficient cic compensation filter in. Applying third identity, the factor of n down sampler is moved and placed behind the integrator section and before the. The cic decimation hdl optimized block decimates an input signal by using a cascaded integratorcomb cic decimation filter. To see why the cic filter is of interest, first we examine its timedomain behavior, for d 5, shown in figure 3. Cascadeintegrator comb hogenauer resampling filter fred harris. On the other hand, the techniques relying on sharpening of combbased filters in 18 24 are effective because they can take advantage of the structure proposed in 18, which filtsrs the recursive form of comb filters resulting in cascaded integratorcomb comb cic like architectures that move part of the filtering at lower rate. The cic filter is a preferred technique for this purpose. Hogenauer s bit pruning theory refer to states that one valid design criterion is to make the word lengths of the different sections of the filter smaller than b accum as well, so that the roundoff noise introduced by all sections does not exceed the roundoff noise introduced at the output. The cic decimation block performs a sample rate decrease decimation on an input signal by an integer factor. Therefore, cic is a suitable and economical filter architecture for. Cic filter is a preferred technique for this purpose. The cic core supports both interpolator and decima tor types. 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. Vlsi implementation of cascaded integrator comb filters.
Suppose if i am writing a vhdl code for cic interpolation stage for example let differential delay m1, interpolation factor r8,input bit size be 23 and number of comb sections and integrator sections be n9. Cic interpolator example cascade integrator comb filters. The advantages of this paper are using three methods to speed up the cic. 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 paper author presents an optimized design of nonrecursive cic filter structure12. An overview of decimation process and its vlsi implementation. Demystifying hogenauer filters spg technical staff introduction. Since then these filters have found extensive use in decimation and interpolation in. Additionally the cic filter does not require storage for filter coefficients and multipliers as all. The name must begin with a letter and be composed of the following characters. In the bitgrowth section the author has mentioned about the increase in the bits at the output stage. Its frequency response may be tuned by selecting the appropriate number of cascaded integrator and comb filter pairs.
The operation of decimation and digital lowpass filtering is done by cic filters. Examples of highly oversampled systems include channelizers and converters. A digital filter in this class consists of cascaded ideal integrator. Ieee transactions on 2, 155 an economical class of. Hogenauer devised a flexible, multiplierfree filter suitable for hardware implementation, that can also handle arbitrary and large rate changes. In 1617, novel cic filter functions in the explicit compact. The advantage of a cic filter over a fir filter for decimation is that the cic filter does not require any multipliers. Cascaded integratorcomb cic filters are a class of linear phase fir filters comprised of a comb part and an integrator part. They require no multipliers and use limited storage making them an economical alternative to conventional implementations for certain applications. Cic decimation filter block diagram above f igure 4 shows the cic decimation filter block diagram. Cic filter is equivalent to a number of rectangular windows cascaded recursive filter form, and therefore has a more significant. The cic filter first performs the averaging operation, then follows it with the decimation.
Wide band rate conversion using cic filters for wireless. An enhancement of decimation process using fast cascaded. For decimation, the switch subsamples the output of the last integrator stage, reducing the sampling rate from f, to f,r. Selecting the parameters fo r the designing cic filter is explained below. Let me briefly share my understanding on the cascaded integrator comb cic filter, thanks to the nice article. Cic filter cascadeintegrator comb hogenauer resampling filter. In this tutorial, matthew donadio provides continued. Pdf design and implementation of efficient cic filter. Cic filters were introduced to the signalprocessing community, by eugene hogenauer, more than two decades ago, but their application possibilities have grown in recent years. Boxcar multiply free filter tf s m hn h t t 2 s m m 0. The cic filter is used in both up sampling and down sampling applications. The cic filters are most economical for hardware implementation as no. Hogenauer filter cascade integrator comb filters informit. Digital filters for decimation and interpolation 151 allaslngllmaging bands 0 fc fal 1 2 3 3.
Pipelined hogenauer cic filters using fieldprogrammable. But if youre not so interested in the mathematical background, its just a name. Unlike most fir filters, it has a decimator or interpolator built into the architecture. The cic contains two subfilters, the comb and the integrator, which can be applied in either order. The cic filter block diagram is shown in figure 2 figure 2. Hogenauer 2 proposed a filter with an efficient way of performing decimation and interpolation. This filter worked with sampling frequency of 5 mhz. A cic decimator 4 would have n cascaded integrator stages clocked at fs, followed by a rate change by a factor r, followed by. Fortunately, this problem can be alleviated by a compensation filter. Application note 455 understanding cic compensation filters introduction the cascaded integratorcom b cic filter is a class of hardwareefficient linear phase finite impulse response fir digital filters.
Hogenauer, an economical class of digital filters for decimation and interpolation, ieee. The altera cic ip core implements a cascaded integratorcomb cic filter with data ports that are compatible with the avalon streaming avalonst interface. These are known as cascaded integrator comb filterscic filters because their. The transfer function of the cic filter in zdomain is given in 1. The figure at the right shows the hogenauer architecture for a cic interpolator. As it turns out, hogenauer s famous paper was not the first formal document describing and proposing cic filters. If the filter is applied to an upsampling task, the comb filter is placed at the input to the cic filter.
In 1981, eugene hogenauer 2 invented a new class of economical digital filter for decimation called a cascaded integrator comb filter cic or recursive comb filter. It do not require multipliers and uses less amount storage to store the filter coefficients. Cascaded integrator comb cic filters the cascaded integratorcomb cic filter is a class of linear filters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers in the filters. Cic filters also known as hogenauer filters are computationally efficient for extracting baseband signals from narrowband sources using decimation. Cic filters use only adders and registers, and require no multipliers to handle large rate changes. Cic filter cascadeintegrator comb hogenauer resampling. 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. Megacore function implements various cic filters based on hogenauer s method. For understanding the cascaded integrator comb cic filter, firstly let us understand the moving average filter, which is accumulation latest samples of an input sequence figure.
Using cic filters, the amount of passband aliasing or imaging error can be. They are typically employed in applications that have a large excess sample rate. The hogenauer cic filters the cascadeintegrator comb cic a. One efficient implementation of this filter is called cic cascadedintegratorcomb filter proposed by hogenauer hogenauer, 1981. Taylor high speed digital architecture laboratory university of florida gainesville 326116, u. In the fall of 1979 eugene hogenauer was finalizing his development of the cic filter, the filter now used in so many multirate signal processing and communications systems. Implementation of optimized cascaded integrator comb. Hogenauer, an economical class of digital filters for interpolation and decimation, ieee. The cic filter frequency response does not have a wide, flat pass band. If a unitimpulsesequence, a unityvalued sample followed by many zerovalued samples, was applied to the comb stage, that stages output is. In 1981, eugene hogenauer 3 invented a new class of economical digital filter for decimation called a cascaded integrator comb filter cic or recursive comb filter.
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