Cicfilters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. The design and realization of main unit of decimation stage that was the cascaded integrator comb cic filter, the associated half band filters and the droop correction are also designed. In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite. Nice for cascaded integrator comb filters cic filters the problem. Understanding cascaded integratorcomb filters by richard lyons embedded systems design 033105, 02.
Cascaded integratorcomb cic digital filter s are computationall y efficient implementation s of narrowband lowpass filters and ar e often embedded in hardware implementat ions of decimation and. Take n moving average filters in sequence with decimation at the end rearrange all integrators first, and comb filters last, with the decimator in the middle integrator overflows are removed by combs if unsigned math is used and the bit width is at least nlog 2 d. Optimal sharpening of cic filters and an efficient. Cascaded integratorcomb filters james gibbards workshop. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often. Cicdecimator system object decimates an input signal using a cascaded integratorcomb cic decimation filter. Cascaded integratorcomb cic filters the cascaded integrator comb cic filter is a class of linear phase finite impulse response fir digital filters. A cic filter consists of one or more integrator and comb filter pairs. 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. Cascaded integratorcomb cic filter lattice semiconductor. Cic filter introduction understanding cascaded integratorcomb filters. Example of cascaded integrator comb filter in matlab. Implementation of optimized cascaded integrator comb filters.
Cascaded integratorcomb cic filters are a class of linear phase fir filters comprised of a comb part and an integrator part. Similarly iir filter requires less memory and faster. Performance analysis and behaviour of cascaded integrator. Cascaded integratorcomb filters september 7, 2015 september 7, 2015 westcoastdsp i have been working on some projects recently that require large sample rate changes. Pdf understanding cascaded integrator comb filters semantic. Both fir and iir filters are referred as impulse responses. Cascaded integrator comb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware implementations of decimation and. These are known as cascaded integratorcomb filters, or cic filters for short. But ive faced situations where my fpga design couldnt fit because of the additional resource consumption of the fir filters.
The feedforward portion of the cic filter is called the comb sec tion, whose differential delay is. The number of stages n has a direct effect on the frequency response of a cic filter. For a decimating cic filter, the filter starts with cascading some integrator stages, followed by downsampling, and then some comb stages. More stages mean the gain of the cic filter increases. Sep 07, 2015 cascaded integrator comb filters september 7, 2015 september 7, 2015 westcoastdsp i have been working on some projects recently that require large sample rate changes. Decimate signal using cascaded integratorcomb filter.
The block supports real and complex fixedpoint inputs. Your task is to describe in vhdl, debug, and implement a dsp circuit called cascaded integratorcomb cic. Richard lyons, understanding cascaded integrator comb filter. The filters work to reduce artifacts such as dot crawl. My question is more about what the outcome would be if the input of the cic would be an exponential. These filters are used as decimation or interpolation filters and can be effi. Cascaded integratorcomb cic filters, commonly used for antialiasing during interpolation and decimation operations that change the sample rate of a discretetime system. Cascaded integrator comb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware implementations of decimation and interpolation in modern communications. Cic filters do not require multipliers and use a limited amount of storage.
If a unitimpulsesequence, a unityvalued sample followed by many zerovalued samples, was applied to the comb stage, that stages output is as shown in figure 3a. Liu, design of cascade form fir filters with discrete valued coefficients, ieee transactions, acoustic, speech signal processing, vol. Cascading multiple comb and integrator sections together greatly improves outofband attenuation. Cic filters electrical engineering at new mexico tech.
Cascadedintegratorcomb cic filters are utilized in many applications that require. 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. For a more detailed description, refer to cascaded integrator comb filters on. To create an interpolating upsampling cic filter, reverse the stages so that the comb section comes before the downsampling operation and the integrator section is after the downsampler. Implementation of cascaded integrator comb cic filter with. Jul 01, 2007 equivalence of moving average and cic filter. Cascaded integrator comb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware implementations of decimation and interpolation in modern communications systems. Understanding cascaded integratorcomb filters by richard lyons, courtesy of embedded systems programming mar 31 2005 14.
These are known as cascaded integrator comb filters, or cic filters for short. In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite impulse response fir filter combined with an interpolator or decimator. In digital signal processing3, a cascaded integratorcomb cic is an optimized class of finite impulse response filter combined with an interpolator or decimator. To see why the cic filter is of interest, first we examine its timedomain behavior, for d 5, shown in figure 3. Each pairing of integrator and differentiator is called a stage.
Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware implementations of decimation and. Cascaded integrator comb fir filter 2 more fir filter examples. Decimation filter gordana jovanovic dolecek and fernando javier trejo torres 5 understanding cascaded integratorcomb filters by richard lyons embedded systems of the design 6 y. In this equation, n is the number of integratorcomb filter pairs, and r is the rate change factor. Differential delay specify the differential delay of your cic filter as an integer value greater than or equal to 1. Performance evaluation of cascaded integratorcomb cic filter. Cascaded integrator comb filters digital filter design. The cic decimation filter structure consists of n sections of cascaded integrators, followed by a rate change by a factor of r, followed by n sections of cascaded comb filters. A noninteger cic interpolation filter is provided for use in sigmadelta digitaltoanalog systems, which realizes noninteger interpolation but eliminates the need for coupling of the integrators in the output domain.
Design cascaded integratorcomb cic filter simulink. An enhancement of decimation process using fast cascaded. In digital signal processing3, a cascaded integrator comb cic is an optimized class of finite impulse response filter combined with an interpolator or decimator. Let me briefly share my understanding on the cascaded integrator comb cic filter, thanks to the nice article. Using cic filters can cut costs, improve reliability, and help performance. The figure above shows a 3stage cic decimator, and illustrates the hardware simplicity. Singlestage cic filter timedomain responses when d 5 view fullsized image.
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. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware. The recursive comb filters or cascaded integrator comb filter cic are commonly used as decimators for the sigma delta modulators. Decimate signal using cascaded integratorcomb cic filter. A beginners guide to cascaded integratorcomb cic filters. An economical class of digital filters for decimation and interpolation, ieee trans. This article is available in pdf format for easy printing. Cascaded integratorcomb cic filters, also known as hogenauer filters, are used to achieve arbitrary and large sample rate changes in digital systems. Cic filters were introduced to the signalprocessing community, by eugene hogenauer, more. Sign up cascaded integrator combcic filter implemented in.
Equation 3 implies that the equivalent time domain impulse response of a cic filter can be viewed as a cascade of n rectangular pulses. Understanding cascaded integratorcomb filters cic filters. When you design either a decimator or interpolator, the resulting filter is a cic filter that decimates or interpolates your input signal. The exact structure of each stage, and the way of connecting all stages together are. The dpoint movingaverage filter s output in time is expressed as. Design of five stage cic decimation filter for signal. These filters are used as decimation or interpolation filters and can be efficiently implemented without multipliers, utilizing only adders and subtractors. In a cic filter, both the integrator and comb sections have the same number of integrators and differentiators.
As i mentioned above is that the only thing i see on my spectrum analyser is the frequency. It is the most practical way to make use of when making regular filter. Fir generally assures stability, which is characterized by changing the power of coefficient. The cascaded integrator comb cic 2 filter is a digital filter which is employed for multiplierless realization of filters. Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications 3. Signal processing techniques for software radio behrouz farhangboroujeny department of electrical and computer engineering university of utah c 2007, behrouz farhangboroujeny, ece department, university of utah.
Implementation of optimized cascaded integrator comb. Vlsi implementation of cascaded integrator comb filters for. Ipug42 cascaded integratorcomb cic filter ip users guide. Cic filters were introduced to the signalprocessing community by eugene hogenauer over two decades ago. The cascaded integrater comb filter is an efficient way of implementing lowpass filters and is particularly useful for sampling rate conversion using decimation or interpolation. Number of combs sections must equal number of integrators.
In its normal mode of operation, the cic decimation block allows the adders numeric values to overflow and wrap around 1 3. At this point, other options need to be considered and cascaded integratorcomb filters are a good one. The cascaded integrator comb cic filter, or hogenauerfilter, is a multiplier less filter architecture that is extremely important for implementing area efficient high sample rate changes in digital down converters ddc and digital up converters duc. This paper presents the vlsi implementation, analysis and design of high speed cic filters which are based on a lowpass filter. Cascaded integratorcomb cic digital filters are computationallyefficient. A cascaded integrator comb cic filter is a special class of linear phase, finite impulse response fir filter. Understanding cascaded integratorcomb filters cic and. Figure 7 shows a cascaded nstage decimation cic filter where the integrators and combs are. Multirate filters alter sampling rates even after youve captured the data, edn, august 20, 1992. Cascaded integrator comb fir filter 2 iowegian international.
Cascaded integrator comb cic filters are one of the most economical multirate filters widely used as decimators in digital receivers. Cascaded integratorcomb cic filter introduction dspguru. Coherent and incoherent gain in cic integrators cascade. Us7324025b1 noninteger interpolation using cascaded.
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