Implementation of cascaded integrator comb cic filter. Design cascaded integratorcomb cic filter simulink. Vlsi implementation of cascaded integrator comb filters for. The number of stages n has a direct effect on the frequency response of a cic filter. Implementation of optimized cascaded integrator comb. Ipug42 cascaded integratorcomb cic filter ip users guide. In the case of a decimating cic, the input signal is fed through one or more cascaded integrators, then a downsampler, followed by one or more. Hogenauer devised a flexible, multiplierfree filter suitable for.
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. The cascadedintegratercomb filter is an efficient way of implementing lowpass filters and is particularly useful for sampling rate conversion using decimation or interpolation. Understanding cascaded integratorcomb filters cic filters. Jul 01, 2007 equivalence of moving average and cic filter. Vlsi implementation of cascaded integrator comb filters. Understanding cic compensation filters pdf free download. The five stage cic filter is proposed in this paper. Fir generally assures stability, which is characterized by changing the power of coefficient. Performance evaluation of cascaded integratorcomb cic. Cascaded integratorcomb 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. An economical class of digital filters for decimation and interpolation, ieee trans.
Pdf understanding cascaded integrator comb filters semantic. The response of the filter is determined by configuring the number of stages n, the rate change factor r and the number of. 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. This paper presents the vlsi implementation, analysis and design of high speed cic filters which are based on a lowpass filter. The two basic building blocks of a cic filter are an integrator and a comb. Cascaded integratorcomb cic filters, commonly used for antialiasing during interpolation and decimation operations that change the sample rate of a discretetime system 2d and 3d comb filters implemented in hardware and occasionally software for pal and ntsc television.
The cascaded integrator comb filters cic find many applications in recent electronic devices such as frequency selection functions in a digital radio or modem and any filter structure that is required to efficiently process large sample rate factor. But ive faced situations where my fpga design couldnt fit because of the additional resource consumption of the fir filters. 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. Interpolate signal using cascaded integratorcomb filter. The dpoint movingaverage filter s output in time is expressed as. It is the most practical way to make use of when making regular filter. Cascaded integratorcomb cic filters are a class of linear phase fir filters comprised of a comb part and an integrator part. Cic filter introduction understanding cascaded integrator comb filters. The previously obscure cic filter is now vital to many highvolume wireless communications tasks and equipment. Design of cascadedintegratorcomb filter for psk modem by. Cicfilters achieve sampling rate decrease decimation and sampling rate increase interpolation without using. Implementation of optimized cascaded integrator comb filters.
At this point, other options need to be considered and cascaded integratorcomb filters are a good one. 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. Understanding cic compensation filters april 2007, ver. 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. Performance analysis and behaviour of cascaded integrator. For a decimating cic filter, the filter starts with cascading some integrator stages, followed by downsampling, and then some comb stages. The figure above shows a 3stage cic decimator, and illustrates the hardware simplicity.
Cic filters were introduced to the signalprocessing community by eugene hogenauer over two decades ago. Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications 3. A implementation of a cascaded integrator comb filter for the cortex m4, designed to have an api similar to cmsisdsp. 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. Introduction in many applications such as digital radio receivers, cascade of decimation filters appears see figure 1 for an example. This article discusses the behavior, mathematics, and implementation of cascaded integratorcomb filters. The cascaded integratorcomb cic filters are used as decimation filter.
Cascaded integrator comb cic filters the cascaded integrator comb cic filter is a class of linear filters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers in the filters. Assuming that i have as input iq samples from a signal generator that are multiplied over a complex multiplier by another set of iq samples. Cic filters do not require multipliers and use a limited amount of storage. The recursive comb filters or cascaded integrator comb filter cic are commonly used as decimators for the sigma delta modulators. Cic filters electrical engineering at new mexico tech. In a cic filter both the integrator and comb sections have.
Example of cascaded integrator comb filter in matlab. These filters are used as decimation or interpolation filters and can be efficiently implemented without multipliers, utilizing only adders and subtractors. Cicdecimator system object decimates an input signal using a cascaded integratorcomb cic decimation filter. Design of five stage cic decimation filter for signal. A beginners guide to cascaded integratorcomb cic filters. It does not require any multiplier circuit and also uses recursive or nonrecursive filter4. I would like to ask something regarding cics cascaded integratorcomb filters or more particular about the frequency response of it. Cic is the combination of equal number of integrator and comb stages. In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite impulse response fir filter combined with an interpolator or decimator a cic filter consists of one or more integrator and comb filter pairs. Implementation of cascaded integrator comb cic filter with. Also provided is a description of cascaded integratorcomb cic filters, along with filter requirements for a given deltasigma adc.
These filters are used in the signal decimation which has the effect on reducing the sampling rate. This paper sumarizes the ndings published in hog81. The feedforward portion of the cic filter is called the comb sec tion, whose differential delay is. Cascaded integratorcomb filters september 7, 2015 september 7, 2015 westcoastdsp i have been working on some projects recently that. 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. My question is more about what the outcome would be if the input of the cic would be an exponential.
Cascaded integrator comb filters digital filter design. These are known as cascaded integratorcomb filters, or cic filters for short. Cascaded integratorcomb cic filter lattice semiconductor. The filters work to reduce artifacts such as dot crawl. 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. These are known as cascaded integratorcomb lters, or cic lters for short. In digital signal processing3, a cascaded integratorcomb cic is an optimized class. A cic filter consists of an equal number of stages of ideal integrator followed by comb filters. A cascaded integrator comb cic filter is a special class of linear phase, finite impulse response fir filter. Us7324025b1 noninteger interpolation using cascaded. The present noninteger interpolation filter provides for more attenuation to all of the aliases of the input signal and has eliminated the need of complex computations.
A cic filter consists of one or more integrator and comb filter pairs. Exploring decimation filters high frequency electronics. Understanding the phasing method of single sideband. Decimate signal using cascaded integratorcomb filter. Cascaded integratorcomb cic filters, commonly used for antialiasing during interpolation and decimation operations that change the sample rate of a discretetime system. To reduce hardware requirements, filter with only few coefficients or a cascaded integratorcomb cic filter is used on the top position, working on the highest sampling. Specify the differential delay of your cic filter as an integer value greater than or equal to 1. The second is to remove the entire outofband signals and noise. These curves were generated in a manner similar to the process described in the up sampling cic example. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass. These filters are normally located after the sigma delta modulator and have regular structure. Using cic filters can cut costs, improve reliability, and help performance.
When you design either a decimator or interpolator, the resulting filter is a cic filter that decimates or interpolates your input signal. Coherent and incoherent gain in cic integrators cascade. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware. In the classic paper, an economical class of digital filters for decimation and interpolation, hogenauer introduced an important class of digital filters called cascaded integrator comb, or cic for short also sometimes called hogenauer filters. Sample rate conversion from understanding digital signal processing. Both fir and iir filters are referred as impulse responses. Differential delay specify the differential delay of your cic filter as an integer value greater than or equal to 1. 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. Liu, design of cascade form fir filters with discrete valued coefficients, ieee transactions, acoustic, speech signal processing, vol.
Generalized comb decimation filters for ad converters. Let me briefly share my understanding on the cascaded integrator comb cic filter, thanks to the nice article. Cascaded integrator comb fir filter 2 more fir filter examples. In its normal mode of operation, the cic decimation block allows the adders numeric values to overflow and wrap around 1 3.
Performance evaluation of cascaded integratorcomb cic filter. In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite. Frequency magnitude response of a decimateby2 compensation fir filter. Appendix a of the downloadable pdf file associated with. Cic filters decimation filters perform several important functions. To summarize, a cic decimator would have n cascaded integrator stages clocked at. For understanding the cascaded integrator comb cic filter, firstly let us. Cic filters were introduced to the signalprocessing community, by eugene hogenauer, more. 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. There we see that the current input sample x n is added, and the oldest input sample x n d is subtracted from the previous output average y n 1. Dsp system toolbox filtering multirate filters description the cic interpolation block performs a sample rate increase interpolation on an input signal by an integer factor. The block supports real and complex fixedpoint inputs. Cic filters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers.
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. Cascaded integratorcomb cic filter introduction dspguru. In a cic filter, both the integrator and comb sections have the same number of integrators and differentiators. 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. Pdf understanding cascaded integratorcomb filters researchgate. 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.
They are computationally efficient implementations of narrowband lowpass filters, which make them wellsuited as antialiasing filters. In digital signal processing3, a cascaded integratorcomb cic is an optimized class of finite impulse response filter combined with an interpolator or decimator. Cascaded integratorcomb cic filters the cascaded integrator comb cic filter is a class of linear phase finite impulse response fir digital filters. Cascaded integrator comb fir filter 2 iowegian international. Each pairing of integrator and differentiator is called a stage. Understanding cascaded integratorcomb filters cic and. 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.
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. The cascaded integrator comb filters cic find many applications in recent. This paper discusses the implementation of cascadedintegratorcomb filter cic which is a higher order decimation filter for the pulseshaping of the digital data for psk modem. Example of cascaded integrator comb filter in matlab dsplog. In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite impulse response fir filter combined with an interpolator or decimator. Cascaded integratorcomb cic filters, also known as hogenauer filters, are used to achieve arbitrary and large sample rate changes in digital systems. The first is to downsample and reduce the clock rate.
As i mentioned above is that the only thing i see on my spectrum analyser is the frequency. The differential delay changes the shape, number, and location of nulls in the filter response. Comb filters are used in a variety of signal processing applications. Application note 455 understanding cic compensation filters introduction the cascaded integrator com b cic filter is a class of hardwareefficient linear phase finite impulse response fir digital filters. 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. These filters are used as decimation or interpolation filters and can be effi. Similarly iir filter requires less memory and faster. Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications. Introduction of c programming for dsp applications.
Cicfilters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. Decimate signal using cascaded integratorcomb cic filter. They have found a particular niche in digital transmitters and receivers. Cascaded integratorcomb 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. 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. 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.