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. Modulation and demodulation techniques for fpgas ray andraka p. Vlsi implementation of cascaded integrator comb filters for. 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. Fast dsp processors can handle complex combinations of filters in parallel or cascade series. A deltasigma adc generally comprises a deltasigma modulator, followed by a decimation filter. Number of integrator and comb stages must be equal. Cicfilters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. An interesting fourier transform 1f noise steve smith. Decimate signal using cascaded integratorcomb filter. These filters are used as decimation or interpolation filters and can be effi. Cascaded integratorcomb cic digital filters are computationallyefficient implementations of narrowband lowpass filters, and are often embedded in hardware implementations of decimation, interpolation, and deltasigma converter filtering. 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.
This means that, theoretically, a datum an infinite time in the past still affects the current average. However, no responsibility is assumed by analog devices for its use, nor for any. A beginners guide to cascaded integratorcomb cic filters. Use the digital down converter ddc system object to emulate the ti graychip 4016 digital down converter in a simple manner. The recursive comb filters or cascaded integrator comb filter cic are commonly used as decimators for the sigma delta modulators. Cascaded integratorcomb cic filters the cascaded integrator comb cic filter is a class of linear phase finite impulse response fir digital filters.
Pdf understanding cascaded integrator comb filters semantic. These are known as cascaded integrator comb filters, or cic filters for short. Performance evaluation of cascaded integratorcomb cic. They are typically employed in applications that have a large excess sample rate. The cic interpolation block performs a sample rate increase interpolation on an input signal by an integer factor. 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. The second is to remove the entire outofband signals and noise. Implementation of optimized cascaded integrator comb. This paper discusses the implementation of cascaded integratorcomb filter cic which is a higher order decimation filter for the pulseshaping of the digital data for psk modem. The next step in our journey toward understanding cic filters is to consider an equivalent. I would like to ask something regarding cics cascaded integratorcomb filters or more particular about the frequency response of it.
Number of combs sections must equal number of integrators. A simulation study has been made for the filters, cascade integrator comb cic, half band hbf and. The cascaded integratorcomb filter consists of a comb and integrator as the name suggests. Exploring decimation filters high frequency electronics. The frequency response of the moving average filter is. The data rate out of cic2, f samp2, is determined by the decimation factor, m. 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 do not require any multiplier circuits and hence are very economical for implementation in hardware and the problems with cascading faced by the accumulate. An enhancement of decimation process using fast cascaded integrator comb cic filter conference paper pdf available november 2006 with 755 reads how we measure reads. The cascaded integrator comb cic filter is a class of linear phase finite impulse response fir digital 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.
Cascaded integratorcomb cic digital filters are computationally efficient. A cascaded integrator comb cic filter is a special class of linear phase, finite impulse response fir filter. Vhdl implementation of optimized cascaded integrator comb. Cicdecimator system object decimates an input signal using a cascaded integratorcomb cic decimation 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. The first is to downsample and reduce the clock rate.
Ad9856 cmos 200 mhz quadrature digital upconverter data sheet. Magnitude response of a 1storder, d 8, decimating cic filter. Rate options when the filter type parameter specifies a multirate filter, select the rate processing rule for the block from following options. This paper sumarizes the findings published in hog81. Cascaded integratorcomb filters james gibbards workshop. 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. Much of the following explanation on hogenauer pruning is taken from 1 and 2. This leads to the following transfer function with respect to the input sample rate.
A cic filter consists of an equal number of stages of ideal integrator followed by comb filters. Vhdl implementation of optimized cascaded integrator comb cic filters for ultra high speed wideband rate conversion international journal of scientific engineering and technology research volume. This paper presents the vlsi implementation, analysis and design of high speed cic filters which are based on a lowpass filter. First, this is a general configuration for a cascaded filter order greater than 1. Us7324025b1 noninteger interpolation using 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. Cic filters were introduced to the signalprocessing community, by eugene hogenauer, more. Implementation of optimized cascaded integrator comb filters.
Implementation on combined cic filter and 64 taps using. 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. As the system is linear, the position of the integrator and comb stage can be swapped. I would like to ask something regarding cics cascaded integrator comb filters or more particular about the frequency response of it. Cic filters decimation filters perform several important functions. Cic filters are a computationally efficient way to perform interpolation and decimation using a higher order n cic gives greater stopband attenuation the differential delay m should only be 1 when the bandwidth of the signal of interest is small compared with the lower sample rate of the cic filter. In this particular design the comb filter will precede the integrator. Cascaded integrator comb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware implementations of decimation and.
In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite impulse response fir filter combined with an interpolator or decimator. Take n moving average filters in sequence with decimation at the end. 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. Cascading multiple comb and integrator sections together greatly improves outofband attenuation. The filters work to reduce artifacts such as dot crawl.
Cascaded integrator comb filters digital filter design toolkit. The data rate into this stage equals the input data rate, f samp. These filters are used in the signal decimation which has the. In the next few slides the cascaded integratorcomb filter is examined. Understanding digital signal processing third edition richard g. Cascaded integratorcomb filters response same as m cascaded nr boxcar filters high order multiplierless interpolation or decimation constant response relative to decimated sample rate. This article discusses the behavior, mathematics, and implementation of cascaded integratorcomb filters. An extension of cic lters has been published in kjw97, and is brie y mentioned here. Now, using a small matlab code snippet let us verify that the output from cic realization is indeed the same as obtained from moving average filter. 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. We base the example on a comparison with the gsm digital down converter example. Cascaded integratorcomb cic digital filters are computationally efficient implementations of narrowband lowpass filters and are often embedded in hardware. Also provided is a description of cascaded integratorcomb cic filters, along with filter requirements for a given deltasigma adc. In this tutorial, matthew donadio provides continued.
Cic filters were introduced to the signalprocessing community. They have found a particular niche in digital transmitters and receivers. Deltasigma modulation is one of the most effective. Cascaded integrator comb cic filters are a class of linear phase fir filters comprised of a comb part and an integrator part. Cic filters also known as hogenauer filters are computationally efficient for extracting baseband signals from narrowband sources using decimation.
Design cascaded integratorcomb cic filter simulink. 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. Pdf understanding cascaded integratorcomb filters researchgate. Design of five stage cic decimation filter 353 where m denoted as a decimation factor. Performance evaluation of cascaded integratorcomb cic filter. 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. Cascaded integratorcomb cic filters, commonly used for antialiasing during interpolation and decimation operations that change the sample rate of a discretetime system. 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.
This article is available in pdf format for easy printing. In digital signal processing, a cascaded integratorcomb cic is an optimized class of finite. A functional model of the cic compensation filter is developed using the matlab program. Cascaded integratorcomb cic digital filters are computationallyefficient. Cic filters do not require multipliers and use a limited amount of storage. An enhancement of decimation process using fast cascaded.
Using cic filters can cut costs, improve reliability, and help performance. Example of cascaded integrator comb filter in matlab. A cic filter consists of an equal number of stages. Ipexpresscreated files and top level directory structure. Introduction the cascaded integrator comb filters do not require any multiplier circuits and hence are very economical for implementation in hardware and the problems with cascading faced by the accumulate. These are known as cascaded integratorcomb filters, or cic filters for short. Vlsi implementation of cascaded integrator comb filters. The highlevel implementation provides better compatibility across various filter structures, especially filters that would contain algebraic loops when constructed using basic elements. Application of filter sharpening to cascaded integratorcomb decimation filters pdf a new architecture for the implementation of highorder decimation filters is described. 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. Using the twos complement binary format, with its modular wraparound property, the.
That means a resolution of about 4 ppm full scale per sample. C information furnished by analog devices is believed to be accurate and reliable. Nice for cascaded integrator comb filters cic filters. This filter is known as cascaded integrator comb filter. In digital signal processing3, a cascaded integratorcomb cic is an optimized class of finite impulse response filter combined with an interpolator or decimator. In physical terms, this is equivalent to a simple rc filter and is a type of infinite impulse response iir filter. Assuming that i have as input iq samples from a signal genera.
What links here related changes upload file special pages permanent link page information. The cic decimation block performs a sample rate decrease decimation on an input signal by an integer factor. 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. Therefore, cic filters are more efficient than conventional fir filters, especially in fixedpoint applications. 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. A full copy of the numerical recipes include files is available from. Let me briefly share my understanding on the cascaded integrator comb cic filter, thanks to the nice article.
But ive faced situations where my fpga design couldnt fit because of the additional resource consumption of the fir filters. Ad9856 cmos 200 mhz quadrature digital upconverter data. After cascading the cic filter and the compensation fir filter, i got the following compensated cic filter response. The block supports real and complex fixedpoint inputs. The ad9856 is intended to function as a universal iq modulator and agile upconverter for communications applications where cost, size, power. Cic filter introduction understanding cascaded integratorcomb filters. Pdf the previously obscure cic filter is now vital to many highvolume. Comb filters are used in a variety of signal processing applications.
Cascaded integrator comb filter the present work is to design efficient decimation filter. Understanding the phasing method of single sideband modulation rick lyons. Performance analysis and behaviour of cascaded integrator. This is a second order, cascaded integrator comb fir filter shown as cic2 in figure 1. Cic filters were introduced to the signalprocessing community by eugene hogenauer over two decades ago. 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 filters are generally used in multirate systems with large sampling rate conversion factors. At this point, other options need to be considered and cascaded integratorcomb filters are a good one. The cic interpolation block requires a fixedpoint designer license. Cascaded integratorcomb cic filter introduction dspguru. 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.
The duc and ddc consist of the following important blocks. Cic filter introduction understanding cascaded integrator comb filters. I created an octave script to generate fixed point coefficients for the serial fir filter i used. These are known as cascaded integratorcomb lters, or cic lters for short. Also provided is a description of cascaded integrator comb cic filters, along with filter requirements for a given deltasigma adc. Jul 01, 2007 equivalence of moving average and cic filter. Sample rate conversion from understanding digital signal processing. It combines the cascaded integratorcomb cic multirate filter. Digital filters are very much more versatile in their ability to process signals in a variety of ways.
Cmos 200 mhz quadrature digital upconverter ad9856 rev. There are a couple of reasons why to configure the comb before the integrator. Understanding cascaded integratorcomb filters cic and. This paper sumarizes the ndings published in hog81. A cic filter consists of one or more integrator and comb filter pairs. Sep 07, 2015 one of the amazing properties of cic filters is that each integrator stage is allowed to overflow, but the resulting output of the filter doesnt overflow if the filter is designed using 2s complement arithmetic and the filter bit width is wide enough to accomodate the maximum value at the output. The compensated cic filter response is much flatter in the passband region and the stopband suppression is around 100 db. Understanding deltasigma modulators electronic design. Ipug42 cascaded integratorcomb cic filter ip users guide. More stages mean the gain of the cic filter increases. Design of five stage cic decimation filter for signal. The next step in our journey toward understanding cic filters is to consider. Cic filters achieve sampling rate decrease decimation and sampling rate increase interpolation without using multipliers. Interpolate signal using cascaded integratorcomb filter.
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