## Forums Search for: Multirate

## dspGuru Multirate Code Question

inHi, In interp.c - interp(), the while loop decrements the input sample counter first. while (--num_inp > 0) { So won't it miss the last...

Hi, In interp.c - interp(), the while loop decrements the input sample counter first. while (--num_inp > 0) { So won't it miss the last input sample? Not that you would ever call interp() one sample at a time, but if you did, it would do nothing. --num_inp would make the 1 a 0 and the while test would be while (0 > 0) { which would do nothing. So shouldn't be a post decrement

## 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...

## Fractional Decimation in DSP

Hi, Friends! Recently, I have some questions about Fractional Decimation. I think about them for a lot of time, but can't find a good...

Hi, Friends! Recently, I have some questions about Fractional Decimation. I think about them for a lot of time, but can't find a good solution. It comes from my reading Douglas W.Barker's paper "Efficient Resampling Implementations " presented on "Tips&Tricks" IEEE Signal Processing Magazine,2008. I found some interrelated materials in Mr. Fred Harris's book < < Multirate signal proces

## 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...

## Down sampling / Halfband filters on DSP

inHello! I need to implement a low pass filter with a flexible cut-off frequency of 10-50Hz for signals sampled at 40kHz. I believe that for...

Hello! I need to implement a low pass filter with a flexible cut-off frequency of 10-50Hz for signals sampled at 40kHz. I believe that for this approach a multirate and multistage filter is the best choose. So first the signal is down-sampled by a factor of approximately 100, then the signal is filtered with an IIR filter and finally the signal is up-sampling (may up-sampling is not required)...

## Xilinx FIR Core Implementation

inHi, I've built a FIR filter in Matlab, and used to the coefficients in Xilinx Coregen to build a multirate lowpass decimator (16x)....

Hi, I've built a FIR filter in Matlab, and used to the coefficients in Xilinx Coregen to build a multirate lowpass decimator (16x). According to Matlab, and the Xilinx Coregen graph, I should be getting 120dB of attenuation in the stopband. However, in real life when I hook my fpga board to a signal generator, I only get around ~50dB of attenuation between a tone in the passband and a tone...

## Multirate filter design

inHello All, The task is to design the multiple cascaded FIR filters to do the decimation. There are tough requirements about the resultant...

Hello All, The task is to design the multiple cascaded FIR filters to do the decimation. There are tough requirements about the resultant ripples in the passband; the stage-by-stage design seems to be very inefficient. Can you suggest a filter design software which can optimize the overall response of the cascaded decimator? Also it would be nice if it can find the optimal decimation...

## computatable efficient lowpass filters?

inHi, Im looking for computatable efficient lowpass filters. Any suggestions? I have already read about Wave Digital Filters and the CIC filter...

Hi, Im looking for computatable efficient lowpass filters. Any suggestions? I have already read about Wave Digital Filters and the CIC filter (which is a really great multirate filter btw). Thanks in advance

## Using Multirate algorithm for doing pitch shift effect ?

inHi, I'm trying to implements a pitch shift effect (up / down a .wav sound 44100Hz 16bit to different semitones in the range of around 1...

Hi, I'm trying to implements a pitch shift effect (up / down a .wav sound 44100Hz 16bit to different semitones in the range of around 1 octave). My problem is that I need to do it on about 15 sample simultaneously in real time. The classic pitch shift algorithms use too much of processor time. As my samples are looped, I don't care about the lenght modification of my samples. That's why, ...

## Sample rate conversion doubt

inHello guys, I've been struggling with algorithms for sample rate conversion, namely decimation by a factor of 40, to convert from 8kHz sample...

Hello guys, I've been struggling with algorithms for sample rate conversion, namely decimation by a factor of 40, to convert from 8kHz sample rate to 200 Hz. I've started with the block diagrams from P.P. Vaidyanathan's book "Multirate Systems and Filter Banks" implementing them in Simulink, and then writting my own C code. From the Simulink model everything was OK. But my C code (runni...

## Frame-based resampling in MATLAB?

inBack in Apr 25, 2004, MC Canzee posted a query in comp.soft-sys.matlab that said (in part): > i want to resample frame-based. > Therefore i...

Back in Apr 25, 2004, MC Canzee posted a query in comp.soft-sys.matlab that said (in part): > i want to resample frame-based. > Therefore i need a filter, that returns filterstates. > Like e.g. [y,zf] = filter(b,a,x,zi) does. > But due to resampling process this filter should be multirate to be > efficient, like e.g. upfirdn(); > The problem with upfirdn is that it does not return filte

## Group Delay of Multirate multistage system

inHi all, I have a question please? I have an input signal with 1.5 Mhz sampling rate. I have a serial of FIR filters which are used to...

Hi all, I have a question please? I have an input signal with 1.5 Mhz sampling rate. I have a serial of FIR filters which are used to interpolate this signal. The first filter interpolate the signal by 2 which works on 3 Mhz, the second one interpolate the signal by 1.5 which work on 4.5 Mhz. Could you tell me please how can I calculate the group delay of the overall system. I have an ...

## multirate filter design

inHi, When one designs a fractional rate change filter, when specifying the filter parameters do you design the filter at the interpolated rate...

Hi, When one designs a fractional rate change filter, when specifying the filter parameters do you design the filter at the interpolated rate or the decimated rate? For example if you have an input rate of Fs then interp by 64 decimate by 125 filter and the filter will be implemented in a P/Q polyphase fashion do you design the filter at the 64*Fs rate? Assuming that the signal is alr...

## How to get a segment of the magtitude response of a filter?

inHi, I am designing a decimation multirate filter with CIC and the decimated rate is very large . It could be larger than 1,000,000....

Hi, I am designing a decimation multirate filter with CIC and the decimated rate is very large . It could be larger than 1,000,000. The difficult I face is that when the decimated rate is too large , I can't view the details of the magnitude response of the passpand. In order to get the details of the magnitude response , the freqz function in matlab need to carry out a FFT with million...

## using IIR or FIR to implement the lowpass filter for downsampling?

inFor downsampling (decimation) one normally uses low pass filter before downsampling (anti-aliasing filter). I have thought that FIR is the...

For downsampling (decimation) one normally uses low pass filter before downsampling (anti-aliasing filter). I have thought that FIR is the best choice here for the low pass filter implementation for this case. But I was reading this page: http://www.dspguru.com/dsp/faqs/multirate/decimation and it said in 2.3.1 under "How do I implement decimation?" "To implement the filtering part...

## decimation filter delay

Hi members I am new to multirate dsp ,I understand that to down sample you need to have antialias filter bandlimited to Fs/2(Fs output sampling...

Hi members I am new to multirate dsp ,I understand that to down sample you need to have antialias filter bandlimited to Fs/2(Fs output sampling rate)and take the M (decimation factor)samples and discard M-1 samples. My questions are 1)Is antialias filter itself called decimation filter 2) delay in FIR filter is given as (N-1)/2 (N. no of taps) ,what is the formula if I decimate by factor M, a...

## some suggestions on my octave-band spectrogram analysis in fixed point DSP implementation

ini am designing one 1/3 octave band spectrogram analysis I use multirate filter bank to realize that spectrogram. It goes this way 1) first,...

i am designing one 1/3 octave band spectrogram analysis I use multirate filter bank to realize that spectrogram. It goes this way 1) first, from the biggest frequency value, I use three IIR bandpass filter, then calculate the std value. 2) Then decimate the input by 2 through(one 30 order FIR filter, then resampling the input), then use the same three coffeicents to calculate the succ...

## Design of FIR filter with Sharp Transition and High Stop Band Attenuation

inHi I have to design a FIR filter with very steep transition at cutoff and high stop ban attenuation. FIR bcoz I need linear phase. I have...

Hi I have to design a FIR filter with very steep transition at cutoff and high stop ban attenuation. FIR bcoz I need linear phase. I have matlab available. Fdatool is useless since its FIR dont have a good transition. In literature search I came by papers talking about Sharp transition FIR`s using Frequency response masking and multirate filters. I wanted to know if someone has any experien...

## Monotonicity of allpass phase function

inI have looked at P.P. Vaidayanthan's "Multirate Systems and Filter Banks" on the topic of the monotonicity of the unwrapped phase response of an...

I have looked at P.P. Vaidayanthan's "Multirate Systems and Filter Banks" on the topic of the monotonicity of the unwrapped phase response of an allpass digital filter. The proof is based on the observation that the group delay is always positive and hence slope of the phase response is always negative, ergo phi(w) is a decreasing function. The group delay > 0 is shown for a first order sec

## Frequency components are added for time domain orthogonal kernels?

Hi, I am reading the book of multirate signal processing written by Harris. On page 47, the windowed filter design technique is introduced. It...

Hi, I am reading the book of multirate signal processing written by Harris. On page 47, the windowed filter design technique is introduced. It mentioned the frequency domain components for two orthogonal time domain kernels are added. It is a right conclusion for any orthogonal time domain kernels? I cannot find the derivation for that conclusion. Can you explain it further to me? Thanks.