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