## Forums Search for: Decimation

## decimation and anti-aliasing

inDear all, Thanks for all your replies but I am still a bit confused. Let me try rephrasing my question so that everyone gets a better picture...

Dear all, Thanks for all your replies but I am still a bit confused. Let me try rephrasing my question so that everyone gets a better picture of what I am trying to do. I have a large number (order of 10^13) of discretized data samples. I have to obtain the frequency spectrum of this data so that I can predict minima in the discretized data. I am using the FFTW C library to obtain the Frequency...

## wcdma bandwidth

inif you were designing a decimation filter for a baseband wcdma signal that was oversampled, what target (decimated) bandwidth would you...

if you were designing a decimation filter for a baseband wcdma signal that was oversampled, what target (decimated) bandwidth would you choose? -- Randy Yates % "Maybe one day I'll feel her cold embrace, Digital Signal Labs % and kiss her interface, mailto://yates@ieee.org % til then, I'll leave her alone." http://w...

## Design of multirate filters

inHi i am simulating a baseband OFDM system Digital down converter. I have a problem regarding decimation and interpolation. In the last stage of...

Hi i am simulating a baseband OFDM system Digital down converter. I have a problem regarding decimation and interpolation. In the last stage of the DDC, i am doing low pass filtering of the data. My problem is when i make a sharp transition filter i.e. ( Fpass = 250e3; % Passband Frequency Fstop = 300e3; % Stopband Frequency the OFDM constellation is scattered. But...

## Re: Interpolation

inEric Jacobsen wrote: > > On Tue, 01 Apr 2008 19:37:07 -0600, jim > wrote: > > > > > > > Eric Jacobsen wrote: > > > >...

Eric Jacobsen wrote: > > On Tue, 01 Apr 2008 19:37:07 -0600, jim > wrote: > > > > > > > Eric Jacobsen wrote: > > > > > > If the process requires an AA filter to reduce bandwidth they > > > > "necessarily" will. > > > > > > Back to my previous example with a solitary tone in a unity gain > > > passband. If the decimation rate is integer and the samples are no

## Interpolation using polyphase FIR filter: Finding coeffisients

inHi, I have a datastream that is sampled 4800 times pr second, but the rf front end I am going to use accepts only input at 250000 samples pr...

Hi, I have a datastream that is sampled 4800 times pr second, but the rf front end I am going to use accepts only input at 250000 samples pr second. Clearly I need a 52,0833 times interpolation. To achieve this I have planned to first interpolate 625 times, and then decimate 12 times. I will do this in steps, for instance in steps of 5 for the interpolation, and 4 for the decimation. I...

## C6713

inHi there, I personally would recommend the C6713 as I used it to learn developing code on a TI platform. There's a good book on it by Rulph...

Hi there, I personally would recommend the C6713 as I used it to learn developing code on a TI platform. There's a good book on it by Rulph Chassaing : http://www.dsprelated.com/books/238.php The book has some good introductory projects (filtering, decimation etc...) and also has a chapter dedicated to some more involved projects which can test the knowledge you've gained in the previous ch...

## Spurious signals in downconverter

inHi, I have written a matlab code for downconverter. I have tried like this. fftsize = 1024; fi = 83; % input...

Hi, I have written a matlab code for downconverter. I have tried like this. fftsize = 1024; fi = 83; % input frequency fs = 200; % sampling frequency flo = 50; % local oscillator frequency order = 15; df = 5; % filter cutoff frequency dfactor = fs / (2 * df); % decimation factor siglen = dfactor * fftsize; sequ...

## FFT By Decimation In Time paper or succinct explanitory resource

inHi All, I have recently completed my DSP course (subject) which is part of my engineering degree and I am very interested in DSP applications...

Hi All, I have recently completed my DSP course (subject) which is part of my engineering degree and I am very interested in DSP applications to Audio in particular. I have decided to undertake a project which involves FFT (probably I will use a Radix-2 to keep it simple for me) in hardware - I will be coding an FFT in VHDL. The main purpose of this project is to own the core functio...

## Upsample/FIR/downsample

inThe example in the upfirdn() - link below - is as follows. L = 147; M = 160; % Interpolation/decimation factors. N = 24*M; h =...

The example in the upfirdn() - link below - is as follows. L = 147; M = 160; % Interpolation/decimation factors. N = 24*M; h = fir1(N,1/M,kaiser(N+1,7.8562)); h = L*h; % Passband gain = L Fs = 48e3; % Original sampling frequency-48kHz n = 0:10239; % 10240 samples, 0.213 seconds long x = sin(2*pi*1e3/Fs*n); % Original signal, sinusoid @ 1kHz y = upfirdn(x,h,L,M); % 9408 samples, still...

## Frequency shift and decimation in the frequency domain

inHello all, I have coded a program that mixes an audio signal with the I/Q outputs of a software NCO, causing a translation in frequency,...

Hello all, I have coded a program that mixes an audio signal with the I/Q outputs of a software NCO, causing a translation in frequency, applies a FIR lowpass to the results and finally does a downsampling. This of course is all done in the time domain. I am wondering if there is a technique that produces the same results, but that works in the frequency domain. I have the feeling that I c...

## uniform filter bank implementation.

inI have a question with regards to going from a polyphase decimation routine and adapting it to an actual filter bank to separate a...

I have a question with regards to going from a polyphase decimation routine and adapting it to an actual filter bank to separate a large bandwidth into smaller subbands. I understand how polyphase filters works, that no problem, I am just stuck on seeing how you make the transistion to a MxL (where M is the number of channels, and L is the lenght of each filter bank).... I have read previo...

## Multirate filters, MATLAB

Hello, Working on the design of decimation filter for multistage, sample rate conversion. I have designed a filter which represents G(z)....

Hello, Working on the design of decimation filter for multistage, sample rate conversion. I have designed a filter which represents G(z). With freqz(b,1,1024) I can plot the frequency response of the filter (the coefficients are in "b"). However, its output will be downsampled by, say M = 10. How to plot the frequency response of G(z^10)? The kind of plot like Figure 4.4-7 (c), in P.P...

## CIC pruning theory

inHello. I have a problem with the implementation (VHDL) of the pruning technique for the CIC. I designed a CIC with this characteristics :...

Hello. I have a problem with the implementation (VHDL) of the pruning technique for the CIC. I designed a CIC with this characteristics : Bin = 16; Decimation : 40; Delay : 1; Stages : 6. I calculated Bmax = 48 bits. So my first CIC written in VHDL used Bmax for all the integrators and combs, and I found the results I expected. The result of the simulation in ModelSim gives some ...

## Relationship between FIR frequency response and each polyphase response

inHi, I'm thinking of this in the context of decimation (but same thing for interpolation). As an example, say we want to decimate by 8. In...

Hi, I'm thinking of this in the context of decimation (but same thing for interpolation). As an example, say we want to decimate by 8. In the frequency domain, our goal is to design a filter that attenuates the frequencies that will alias when we through away 7 samples. You go off and design an FIR filter that gives you say 60dB worst case in the stopbands. So far so good. When comes time to i...

## Low pass filter for sigma delta ADC

inCould some DSP guru please help ? For a sig-delta ADC, how is the cut- off frequency for the low-pass filter determined, given that there is...

Could some DSP guru please help ? For a sig-delta ADC, how is the cut- off frequency for the low-pass filter determined, given that there is also a decimation filter just after that. Any hints, suggestions would be of immense help. Thanks in advance.

## Decimation / downsampling

inHello, I have problem puting the rigth name on the rigth thing: --> In "Discrete-time signal processing" of Oppenheim and schafer : "In...

Hello, I have problem puting the rigth name on the rigth thing: --> In "Discrete-time signal processing" of Oppenheim and schafer : "In general, the operation of reducing the sampling rate (including any prefiltering) will be called downsampling" section 4.6.1 --> In "An overview of sigma-delta converters" in IEEE signal processing of january 1996 vol 13, no 1 it is say "The collectiv

## Timing recovery in HF

Hi all We are designing a 128TCM QAM receiver. Our idea is to take advantadge from the Digital Downconverters (DDC as GC4016 or similar)...

Hi all We are designing a 128TCM QAM receiver. Our idea is to take advantadge from the Digital Downconverters (DDC as GC4016 or similar) to convert from HF to baseband directly ,let's say sampling at 1MHz, then DDC (CIC + decimation filters), and then a DSP system at 50KHz sampling time where the complete receiver will be implmented. The problem we are guessing is about timing recove...

## CIC filter and compensation filter - help

inHi. I'm trying to design a CIC filter wich has decimator factor (R=64), differencial delay (M=1), number of stages (N=2) and sampling...

Hi. I'm trying to design a CIC filter wich has decimator factor (R=64), differencial delay (M=1), number of stages (N=2) and sampling frequency (Fs=256kHz). I used the following matlab code to simulate its behavior: R = 64; %decimation factor N = 5000; %delay buffer depth delayBuffer = zeros(1, N/R); intOut1 = 0; intOut2 = 0; combOut2 = 0; comb2_delay = 0; n = 0:.01:N; x...

## Basic question on upsampling/downsampling

inHi, I am new to DSP and learning about sampling and related topics. I have read a book and visited online sites but still am having...

Hi, I am new to DSP and learning about sampling and related topics. I have read a book and visited online sites but still am having problems understanding : 1. Why do we need a filter (FIR) BEFORE we downmsample when we perform decimation. I understand why for upsampling we need the filtering part but am having problems with the downsampling filter. 2. I understand for a multirate sys...

## Rick Lyons in EETimes!

inI finally got around to picking up the April 4th EET while eating supper tonight and who do I see on the inside of the front page? Rick's got an...

I finally got around to picking up the April 4th EET while eating supper tonight and who do I see on the inside of the front page? Rick's got an article on embedded.com on CIC filters. Cool stuff, man. The competition is tough around here! There is at least one thing in this article I don't get, Rick. You write: Although the gain of an Mth-order CIC decimation filter is (NR)M indivi...