The operation of decimation and digital lowpass filtering is done by cic filters. 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. Cascadeintegrator comb hogenauer resampling filter fred harris. There is a rate change switch between the two filter sections. Cascaded integratorcomb cic filters, also known as hogenauer filters, are multirate filters often used for implementing large sample rate changes in digital systems. That is, the system sample rate is much larger than the bandwidth occupied by the. It has the two basic building blocks of a cic filters are integrator and comb. However, the disadvantage of a cic filter is that its pass band is not flat, which is undesirable in many applications.
For a decimating cic filter, the filter starts with cascading some integrator stages, followed by downsampling, and then some. Applying third identity, the factor of n down sampler is moved and placed behind the integrator section and before the. 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. To see why the cic filter is of interest, first we examine its timedomain behavior, for d 5, shown in figure 3. The altera cic ip core implements a cascaded integratorcomb cic filter with data ports that are compatible with the avalon streaming avalonst interface. The name must begin with a letter and be composed of the following characters. Performance analysis and behaviour of cascaded integrator. Free up phone storage space by uninstalling apps and deleting files you no longer want to keep. Cascaded integratorcomb cic filter introduction dspguru. Fpga ip implements a cascaded integratorcomb cic filter with data ports that are compatible with the avalon streaming interface. 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. A cic filter is cascade connection of simple integrator and comb filter stages. A digital filter in this class consists of cascaded ideal integrator.
Cic filters are a class of linear phase fir filters consisting of a comb part and an integrator part. 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. The name of the core component to be instan tiated. Yes, an ntap delay line fir boxcar filter and the cic filter with n delays in the comb have the same frequency response.
Expanded view of the multistage cic filter gain response figure 3. Cic filters also known as hogenauer filters are computationally efficient for extracting baseband signals from narrowband sources using decimation. In this paper author presents an optimized design of nonrecursive cic filter structure12. Also the design complexity with fir filter can be recovered with the cic filter. Implementation of optimized cascaded integrator comb. Implementation of cic filter for multirate transmission systems. The system function for the composite cic filter referenced to the high sampling rate, f s is. Cic filters efficiently extract baseband signals from narrowband sources using decimation. Hogenauer, an economical class of digital filters for interpolation and decimation, ieee. They require no multipliers and use limited storage making them an economical alternative to conventional implementations for certain applications. Using cic filters, the amount of passband aliasing or imaging error can be.
Singlestage cic filter timedomain responses when d 5 view fullsized image. Hogenauer published a paper on the cic filter c ic stands for cascaded integrator comb. Cic cascadedintegratorcomb filter proposed in 4 is widely used as antialiasing and antiimaging filter due to its simplicity. Cic filter downsampling as you use htc desire 626s, youll accumulate data and fill its storage capacity over time. But if youre not so interested in the mathematical background, its just a name.
Wide band rate conversion using cic filters for wireless. The cic filter frequency response does not have a wide, flat pass band. Cic filter cascadeintegrator comb hogenauer resampling filter fred harris. Design and implementation of efficient cic filter structure for decimation article pdf available in international journal of computer applications 65. The cic filters are most economical for hardware implementation as no. Cic filters also known as hogenauer filters are computationally efficient for extracting baseband signals from narrowband sources using.
Its frequency response may be tuned by selecting the appropriate number of cascaded integrator and comb filter pairs. 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. When theres a sample rate change in between, the comb and integrator, then harris calls such a system a hogenauer filter. On the other hand, if the cic is applied to a downsampling task, the comb filter is placed. Implementation of optimized cascaded integrator comb filters. A class of digital linear phase finite impulse response fir filters for decimation sampling rate decrease and interpolation sampling rate increase are presented. One efficient implementation of this filter is called cic cascadedintegratorcomb filter proposed by hogenauer hogenauer, 1981.
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. 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. The basic concept of cic filter is given in fig, which consists of. This filter worked with sampling frequency of 5 mhz. Vlsi implementation of cascaded integrator comb filters. He claimed this was an economical class of digital filter. Hogenauer 2 proposed a filter with an efficient way of performing. At that time hogenauer worked for a premier signal processing company called esl inc. Here are some tips on how to free up phone storage space. They are typically employed in applications that have a large excess sample rate. Ieee transactions on 2, 155 an economical class of.
The cic core supports both interpolator and decima tor types. An economical class of digital filters for decimation and interpolation preceding unsigned comment. 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. In this tutorial, matthew donadio provides continued. Cic filter is a preferred technique for this purpose. An economical class of digital filters for decimation and interpolation. Additionally the cic filter does not require storage for filter coefficients and multipliers as all. The hogenauer cic filters the cascadeintegrator comb cic a. Yesterday i called hogenauer at his work and briefly described my definition of bmax question. It do not require multipliers and uses less amount storage to store the filter coefficients. Orignal research within cic as a moving average filter the specific equation is equal to equation 11 from hogenauer, eugene b.
Hogenauer, an economical class of digital filters for decimation and interpolation, ieee. Table i passband attenuation for large rate change factors elative bandwidth. 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. These are known as cascaded integrator comb filterscic filters because their. Ddc the decimation filter can be done poly phase and cic based ddc can be implemented in wireless communication systems. Cic filters also known as hogenauer filters are computationally efficient for.
We now examine an example of the use of the hogenauer resampled cic filter. Decimate signal using cascaded integratorcomb filter. Magnitude response of compensated cic filter for l2 figure 3. The advantage of a cic filter over a fir filter for decimation is that the cic filter does not require any multipliers. Examples of highly oversampled systems include channelizers and converters. As it turns out, hogenauer s famous paper was not the first formal document describing and proposing cic filters. Fortunately, this problem can be alleviated by a compensation filter. 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. 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.
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. An economical class of digital filters for decimation and. Cic filter is equivalent to a number of rectangular windows cascaded recursive filter form, and therefore has a more significant. An enhancement of decimation process using fast cascaded. Pdf design and implementation of efficient cic filter.
Cic filter a combination of digital integrator and digital differentiator is known as cic filter. Eric jacobsen gave me the name of hogenauer s employer in silicon valley. The figure at the right shows the hogenauer architecture for a cic interpolator. In the bitgrowth section the author has mentioned about the increase in the bits at the output stage. An overview of decimation process and its vlsi implementation. 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. Megacore function implements various cic filters based on hogenauer s method. Harris, in his multirate book, uses the terms cic and boxcar filter interchangeably. For decimation, the switch subsamples the output of the last integrator stage, reducing the sampling rate from f, to f,r.
The transfer function of the cic filter can be written as. Therefore, cic is a suitable and economical filter architecture for. A cic decimator 4 would have n cascaded integrator stages clocked at fs, followed by a rate change by a factor r, followed by. Multiplierless wideband and narrowband cic compensator. Since then these filters have found extensive use in decimation and interpolation in. The cic filter is a preferred technique for this purpose. If the filter is applied to an upsampling task, the comb filter is placed at the input to the cic filter. A cic filter consists of an equal number of stages of ideal integrator followed by comb filters.
The cic filter finds applications in interpolation and decimation. Decimate signal using cascaded integratorcomb filter simulink. Unlike most fir filters, it has a decimator or interpolator built into the architecture. Below is a block diagram for the cic filter i used. 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. Design of five stage cic decimation filter for signal. Cic filters use only adders and registers, and require no multipliers to handle large rate changes. The cic filters are most economical for hardware implementation as no multiplier circuits are required. Hogenauer devised a flexible, multiplierfree filter suitable for hardware implementation, that can also handle arbitrary and large rate changes. In 1981, eugene hogenauer 2 invented a new class of economical digital filter for decimation called a cascaded integrator. Vlsi implementation of cascaded integrator comb filters for. 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. The cic filter first performs the averaging operation, then follows it with the decimation. 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.
Cascading sharpened cic and polyphase fir filter for. The disadvantage of a cic filter is that its passband is not maximally flat, which is undesirable in many applications 3. Cascaded integratorcomb cic filters are a class of linear phase fir filters comprised of a comb part and an integrator part. Application of hardware efficient cic compensation filter in. Hogenauer devised a flexible, multiplierfree filter suitable for hardware implementation that can also handle. Example of cascaded integrator comb filter in matlab. The cic filter is used in both up sampling and down sampling applications. Hogenauer invented the cic filter structures is economical class of linear phase, fir filter. 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. Taylor high speed digital architecture laboratory university of florida gainesville 326116, u. 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. The cic decimation block performs a sample rate decrease decimation on an input signal by an integer factor. 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.
Cic interpolator example cascade integrator comb filters. If a unitimpulsesequence, a unityvalued sample followed by many zerovalued samples, was applied to the comb stage, that stages output is. Cic filter cascadeintegrator comb hogenauer resampling filter. Example frequency response for n 4, m 1, r 7, and f, i. Hogenauer 2 proposed a filter with an efficient way of performing decimation and interpolation. 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. Let me briefly share my understanding on the cascaded integrator comb cic filter, thanks to the nice article. 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. Here in the figure we are designing cic decimation filter with the help of simulink software in matlab. Ieee transactions on 2, 155 an economical class of digital. The most simple decimation filter is comb filter which does not require multipliers. A cic filter also known as a hogenauer filter can be used to.
The transfer function of the cic filter in zdomain is given in 1. The cic decimation hdl optimized block decimates an input signal by using a cascaded integratorcomb cic decimation filter. The cic filter block diagram is shown in figure 2 figure 2. Garcia department of electronics and computer technology university of granada, 18071 granada, spain email. Hz1r 1zr1z1 n where, r and n are the decimation rate and order of the cic filter. Boxcar multiply free filter tf s m hn h t t 2 s m m 0. In 1617, novel cic filter functions in the explicit compact.
Digital filters for decimation and interpolation 151 allaslngllmaging bands 0 fc fal 1 2 3 3. All content in this area was uploaded by eugene hogenauer on jan 06, 2015. Demystifying hogenauer filters spg technical staff introduction. The cic contains two subfilters, the comb and the integrator, which can be applied in either order. This paper describes decimation process by the focus on high speed implementation of cic filter hogenauer eb 1981.
Selecting the parameters fo r the designing cic filter is explained below. 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. 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. Two easy ways to test multistage cic decimation filters. But the overflow problem isnt discussed in depth therein. Cic decimation filter block diagram above f igure 4 shows the cic decimation filter block diagram. 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. Hogenauer filter cascade integrator comb filters informit. The advantages of this paper are using three methods to speed up the cic. Cic filters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. Pipelined hogenauer cic filters using fieldprogrammable. Cic filter and pfir filter is used to solve the bandwidth issues in both the sections. 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.