Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware implementations of decimation and. Cic filters do not require multipliers and use a limited amount of storage. In a cic filter, both the integrator and comb sections have the same number of integrators and differentiators. These are known as cascaded integratorcomb filters, or cic filters for short. Vlsi implementation of cascaded integrator comb filters for. Cic filter introduction understanding cascaded integratorcomb filters. Cascaded integratorcomb filters september 7, 2015 september 7, 2015 westcoastdsp i have been working on some projects recently that require large sample rate changes.
The recursive comb filters or cascaded integrator comb filter cic are commonly used as decimators for the sigma delta modulators. 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. Figure 7 shows a cascaded nstage decimation cic filter where the integrators and combs are. 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. It is the most practical way to make use of when making regular filter. More stages mean the gain of the cic filter increases. Cascaded integratorcomb filters james gibbards workshop.
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. But ive faced situations where my fpga design couldnt fit because of the additional resource consumption of the fir filters. Us7324025b1 noninteger interpolation using cascaded. A cic filter consists of one or more integrator and comb filter pairs. Implementation of optimized cascaded integrator comb. The cascaded integrator comb cic 2 filter is a digital filter which is employed for multiplierless realization of filters. Nice for cascaded integrator comb filters cic filters the problem. Singlestage cic filter timedomain responses when d 5 view fullsized image. This paper presents the vlsi implementation, analysis and design of high speed cic filters which are based on a lowpass filter.
Example of cascaded integrator comb filter in matlab. Coherent and incoherent gain in cic integrators cascade. Cic filters were introduced to the signalprocessing community by eugene hogenauer over two decades ago. Cascaded integrator comb filters digital filter design. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware. My question is more about what the outcome would be if the input of the cic would be an exponential. Pdf understanding cascaded integrator comb filters semantic. This article is available in pdf format for easy printing. The exact structure of each stage, and the way of connecting all stages together are. Cicfilters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. For a decimating cic filter, the filter starts with cascading some integrator stages, followed by downsampling, and then some comb stages.
Liu, design of cascade form fir filters with discrete valued coefficients, ieee transactions, acoustic, speech signal processing, vol. Cascaded integratorcomb cic filter introduction dspguru. Decimate signal using cascaded integratorcomb cic filter. Understanding cascaded integratorcomb filters cic and. As i mentioned above is that the only thing i see on my spectrum analyser is the frequency. In this equation, n is the number of integratorcomb filter pairs, and r is the rate change factor. Each pairing of integrator and differentiator is called a stage. Performance evaluation of cascaded integratorcomb cic filter. 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 digital signal processing, a cascaded integratorcomb cic is an optimized class of finite. The block supports real and complex fixedpoint inputs. Cascaded integrator comb 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. Cascaded integrator comb cic filters are one of the most economical multirate filters widely used as decimators in digital receivers. 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. Cascaded integratorcomb cic digital filters are computationallyefficient. An enhancement of decimation process using fast cascaded.
Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications. Cic filters were introduced to the signalprocessing community, by eugene hogenauer, more. The filters work to reduce artifacts such as dot crawl. Cascaded integratorcomb cic filters, also known as hogenauer filters, are used to achieve arbitrary and large sample rate changes in digital systems. When you design either a decimator or interpolator, the resulting filter is a cic filter that decimates or interpolates your input signal. Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications 3. 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.
In digital signal processing3, a cascaded integratorcomb cic is an optimized class of finite impulse response filter combined with an interpolator or decimator. At this point, other options need to be considered and cascaded integratorcomb filters are a good one. Cic filters electrical engineering at new mexico tech. Let me briefly share my understanding on the cascaded integrator comb cic filter, thanks to the nice article. 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. 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.
These are known as cascaded integrator comb filters, or cic filters for short. 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. Understanding cascaded integratorcomb filters by richard lyons embedded systems design 033105, 02. Understanding cascaded integratorcomb filters by richard lyons, courtesy of embedded systems programming mar 31 2005 14. In digital signal processing3, a cascaded integrator comb cic is an optimized class of finite impulse response filter combined with an interpolator or decimator. In a cic filter both the integrator and comb sections have.
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. In its normal mode of operation, the cic decimation block allows the adders numeric values to overflow and wrap around 1 3. 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. To see why the cic filter is of interest, first we examine its timedomain behavior, for d 5, shown in figure 3. Your task is to describe in vhdl, debug, and implement a dsp circuit called cascaded integratorcomb cic. Cascaded integrator comb fir filter 2 iowegian international. Sign up cascaded integrator combcic filter implemented in. 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. Using cic filters can cut costs, improve reliability, and help performance.
For a more detailed description, refer to cascaded integrator comb filters on. Understanding cascaded integratorcomb filters cic filters. A beginners guide to cascaded integratorcomb cic filters. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often.
Cascadedintegratorcomb cic filters are utilized in many applications that require. Fir generally assures stability, which is characterized by changing the power of coefficient. The dpoint movingaverage filter s output in time is expressed as. These filters are used as decimation or interpolation filters and can be efficiently implemented without multipliers, utilizing only adders and subtractors. Implementation of optimized cascaded integrator comb filters. Differential delay specify the differential delay of your cic filter as an integer value greater than or equal to 1. An economical class of digital filters for decimation and interpolation, ieee trans. Cascaded integratorcomb cic filters the cascaded integrator comb cic filter is a class of linear phase finite impulse response fir digital filters. A cascaded integrator comb cic filter is a special class of linear phase, finite impulse response fir filter. Design cascaded integratorcomb cic filter simulink. The feedforward portion of the cic filter is called the comb sec tion, whose differential delay is. Implementation of cascaded integrator comb cic filter with.
Richard lyons, understanding cascaded integrator comb filter. The number of stages n has a direct effect on the frequency response of a cic filter. Design of five stage cic decimation filter for signal. Cascaded integratorcomb cic filter lattice semiconductor. 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. Decimate signal using cascaded integratorcomb filter. These filters are used as decimation or interpolation filters and can be effi. Number of combs sections must equal number of integrators. The figure above shows a 3stage cic decimator, and illustrates the hardware simplicity. Equation 3 implies that the equivalent time domain impulse response of a cic filter can be viewed as a cascade of n rectangular pulses.
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. Jul 01, 2007 equivalence of moving average and cic filter. Both fir and iir filters are referred as impulse responses. Performance analysis and behaviour of cascaded integrator. 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. 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. Cascaded integratorcomb cic filters, commonly used for antialiasing during interpolation and decimation operations that change the sample rate of a discretetime system. Cicdecimator system object decimates an input signal using a cascaded integratorcomb cic decimation filter.
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