Questions tagged [multirate]
The multirate tag has no usage guidance.
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Sample rate change using Lagrange interpolator
I'm trying to understand how to make Sample rate change by a non integer factor say $K=1.0012$
In real hardware I will be using cubic polynomial but for now I have chosen a linear interpolator. I have ...
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Is the following system LTI and what is its purpose?
Above is a block diagram of a discrete-time system $T\{x[n]\} = y[n]$. Here, $h[n]$ is the impulse response of an arbitrary LTI system.
Firstly, is this overall system LTI? I don't think so because ...
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Cascade of Downsample and Upsample
Consider a cascade involving a downsampler (factor $M$) and an upsampler (factor $L$). For the sequence
$$x[n] \rightarrow D \xrightarrow{{v_{1}[n]}} U \rightarrow y[n]$$
where $D$ denotes ...
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Multirate Control System Transfer Functions
I'm interested in oversampling the inputs to a digital controller to increase the SNR of the input process variable signal. I've read on this site and in articles like the one below that it is not ...
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Efficient CIC Decimation Filter in C
Does anyone have advice on efficient CIC Decimation filter implementation. I designed a basic 4th order CIC filter with a 64 decimation ratio in C (below).
I am currently testing this on a Sharc SC589 ...
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Z Transform of M-Fold Decimation
I know this is probably a common question, but after some searching I think that my version of the question is slightly different -- apologies if this is a repeat. I have seen that it is inaccurate to ...
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212
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Decimation: how to preserve frequency content that lie above half the decimated sampling frequency?
I know that with three steps:
complex demodulation
lowpass filtering
decimation
we are able to select frequency contents in a band with reduced sampling rate. But this method only allows frequency ...
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289
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Getting error while performing upsampling of an audio signal processing using low pass filter in python
I want to perform upsampling of an audio signal introducing zeros between samples to create a longer signal with factor of N=2. The sampling rate is 44100Hz, time = 5sec.
...
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Hardware implementation of multi rate FIR filter
I have designed a multi rate fir filter in MATLAB and I want to implement it in verilog.This is the block diagram.
Total number of taps are 391. Is there any way to automatically generate verilog ...
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163
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Direct and Transpose Polyphase Multirate Processing
Polyphase implementations of upsampling/ interpolation and downsampling/ decimation, after having invoked the Noble identities, are presented as follows (taken from Proakis):
(Three-Channel Polyphase ...
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Aliasing Issues in Sub Band Coding
The general structure of Sub-Band Coding (SBC) is shown below:
The diagram shows that after each of the analysis filters, decimation is performed by a factor M which corresponds to the number of ...
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134
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Perfect reconstruction in two-channel filter bank
[from Discrete-time Signal Processing by Oppenheim and Schafer, 3rd ed.]
I was not able to prove this:
If the analysis and synthesis filters are ideal so that they exactly split the band 0 ≤ |ω| ≤ π
...
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282
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Downsampling after a highpass filter
Question: The following sentence is not clear to me (especially why down-shift occurs). Could someone explain it please?
On the other hand, downsampling the output of the highpass filter down-shifts ...
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159
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Interpolated FIR filter (from Oppenheim and Schafer's Discrete-Time Signal Processing, 3rd ed)
[from Discrete-time Signal Processing by Oppenheim and Schafer, 3rd ed., p.196]
Two questions:
In this context, the filter with system function represented by Eq. (103) is called an interpolated FIR ...
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134
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Group Delay of Mulitrate system
how do I find the group delay of multirate system.(sample rate converter) , IIR non-linear phase filter
Say decimation by 2 (with lpf) = tf1(num,den)
then again decimation by 2 (with lpf) = tf2(num,...
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What are the 'phases' in this 2D scaler filter
I am pretty new to DSP and have been looking at how image scaling is done in hardware. I and came across a 2D scaler core for an FPGA here. I have read up a bit about polyphase filters, but am ...
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Where is the mother wavelet defined in the Fast Wavelet Transform?
Referring to the Fast Wavelet Transform, this transform is implemented as a QMF filter bank. This algorithm consists of high/low pass filtering and subsampling. However, a wavelet transform is ...
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215
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What is the multiplication rate in FIR filter
Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency pi/7 and a downsampler by 7. The lowpass filter is a ...
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651
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Decimation FFT Result
In my Signal Processing class we just learned decimation however after messing around in Matlab trying an example of decimation, I just can't understand what's happening.
I get the introducing twi ...
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320
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How to figure out number of multiplications in rational sampling
I am trying to understand the following:
Consider a system implementing a rational sampling rate change by $\frac{5}{7}$: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency $\...
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When is it possible to swap expander and compressor?
In the figure below I want to know when is it possible to swap expander and compressor so that the outputs remain the same?
I know in general it's not possible to interchange because neither expander ...
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79
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Save computational burden by calculating the output of decimate filter at output rate?
I read in a book that the output of a decimate filter can be calculated at output sampling rate. In this way the number of filtering operations can be greatly reduced. But I am wondering how to ...
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Using FFT for implementing a filter bank
I am trying to use Fast Fourier Transform (FFT) for decomposing an audio signal into 8 sub-bands according to this link but the problem is the frequency response of the result contains only the first ...
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687
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Decimating Polyphase Filter in Simulink
I have read many of the articles on the website regarding a polyphase decimating filter structure. I'm sure we are all familiar with the typical image shown in Fred Harris Multirate book and many ...
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What’s a good book on multi-rate dsp?
Was Studying a dsp design recently with many decimation and interpolation filters, and was wondering if there is a recommended book specifically on the subject of multi-rate dsp? Preferably a book ...
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219
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Upsampling with time offsets
Suppose I have done 4x oversampling for a continuous time signal, but the successive sampling times have a linearly increasing offset. Specifically, the samples with indices {4k; k=0, 1, 2,...} are ...
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106
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Using a Multirate FFT system to analyse audio
I am trying to implement a multirate fft system to try and achieve frequency windowed analysis of audio.
Say I have managed to get an impulse response of a system. This impulse may be say one ...
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2
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331
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Drawbacks of upsampling using polynomial interpolation
I've come across an upsampler that uses polynomial interpolation and no filter. What are the drawbacks to this? I looks more efficient than filtering.
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305
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DTFT of even and odd samples
Here to find DTFT of $h(2n)$ they have scaled omega, while in RHS to find DTFT $x(2n+1)$ they didn't, why is that?
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Polyphase components Spectrum formula in Discrete time
I am trying to understand the meaning behind some of the components of the formula for polyphase components in discrete time. Note that $\Omega$ indicates discrete in this notation and the formula is ...
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Converting the equalizer coefficients from VSA at 2 sample/Symbol to 1.5 sample/Symbol
I was looking for some feedback on conversion of equalizer/filter coefficients at different sampler rate.
Problem Statement:
We have built a transmitter system whose output is at 1.5 sample/symbol (...
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112
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What does it mean for a Wavelet transform to commute with translations?
Referencing this article here https://arxiv.org/pdf/1203.1513.pdf
It states "A wavelet transform commutes with translations, and is therefore not translation invariant". Now I understand why it is a ...
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Understanding sampling rate conversion
I am a little bit confused about the concept of sampling rate conversion. Consider the following question:
Wideband telephony signals are sampled at a sampling frequency fS1 = 16kHz. To process these ...
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133
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Sampling rate conversion and polyphase decomposition
Can someone please explain the answer to this problem:
The sampling rate of a baseband signal shall be converted from 5 kHz to 7.5 kHz using the efficient polyphase implementation with a 'rotating' ...
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2
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758
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Reversing the order of up and downsampling
When we are dealing with the problem of changing the sampling rate by a noninteger factor like L/M, we first need to the do the upsampling, and then the downsampling.
My question is that under which ...
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How should I modify my filter coefficients for the filter to be unaltered, when I change my sample rate
I am guessing this is a commonly encountered problem, but I am lost on how to really solve it.
I have FIR filter coefficients that are used to match the frequency response of data sampled at 3 kHz. I ...
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Polyphase Analysis Filter Bank
I have a question regarding the polyphase DFT filter bank implementation in this page. (https://cnx.org/contents/Peqc-TK2@16/Uniformally-Modulated-DFT-Filterbank)
In figure 2, to analyze the kth ...
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Decimator effect on wide sense stationary input
I've seen that the output of a decimator when a WSS process is passed through remains WSS. I am not able to immediately see why this is. What is a good explanation of why the signal maintains ...
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What would be the effect of repeating samples in time domain on frequency domain?
Consider the operation of up-sampling a signal n times by repeating each sample n times in the time domain. What would the frequency domain response of the resultant signal be like given the frequency ...
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Unscented Kalman Filter - Multiple Consecutive Measurement Updates
In trying to implement an Unscented Kalman Filter (UKF), I have come across the issue of what to do when my measurement signals come in at a different rate than my control inputs, which I use in the ...
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How to undo dynamic Doppler effect by software?
I have a signal affected by Doppler effect. In general, the Doppler effect changes the scale of the time and frequency domains. So, to undo this phenomenon, I am using a sampling rate converter. Two ...
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881
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Sampling multiple sensors at different rates
I have a question regarding how best to sample data from multiple sensors when they are all updating at different/changing rates. I am new to data acquisition so please bear with me. For my Master's ...
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231
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Multirate Signal processing for matching DAC of the SDR
I have been breaking my head for a long time. Please help with this..any input would be helpful!
I am trying to implement a OFDM system using SDR (USRPN210 for Transmitter and USRP2 for receiver) ...
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Advantage of complex filtering in multirate applications
I've seen it mentioned in passing in various papers on signal processing and filter design that complex FOR filters can be more efficient when it comes to multirate applications. However I cannot ...
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Extracting narrow-band ZigBee signals(4 MHz) from a wide-band WiFi signal(20 MHz)?
I am planning the following.
First sample the 20 MHz WiFi channel (WiFi channel-1 in figure).
Put band pass filters (5 MHz wide) around each of the ZigBee center frequencies (11, 12, 13, 14).
Re-...
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Why do Dyadic filterbanks downsample the high pass signal portions?
I'm currently programming a dyadic filter bank and have a question. I notice in all of the visual representations:
(from here (Dyadic Analysis Filter Bank)), the high pass filtered output for each ...
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Information Loss in a Multirate System
Assume $M=3$ and $L=2$ for the multirate system shown below. Furthermore, assume an arbitrary fourier transform $X(e^{j\Omega})$. This one lies between $-\pi$ and $\pi$. The fourier transform after ...
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462
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Use polyphase representation to construct a perfect reconstruction filter bank
I'm posting this question in response to Question about zero-phase filter bank
This is a homework question for which I found an answer, but I didn't do it the way I was supposed to. I'm wondering ...
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How do multirate systems introduce 'efficiency' in computation?
I've started reading more into multirate systems recently and am somewhat confused. The concepts introduced seem to make sense, that is, how the decimation and interpolation can change certain ...
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