Questions tagged [equalization]
The equalization tag has no usage guidance.
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Why do inverted impulse responses sound awful when applied to an audio system?
In this answer, the responder claims that acquiring a measured impulse response and straightforwardly inverting it (e.g. by directly in the spectrum, after zero-padding, or by determining the inverse ...
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Why construct a minimum phase filter from measurements?
Sorry if this is a trivial question, but I am not doing signal processing everyday. I will try to express what I think I have understood as best as possible.
Suppose I apply a (linear) sweep signal to ...
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Should we use Maximal ratio combining and an equalizer together?
I have confusion on MRC(Maximal Ratio Combining) method which I would like to clarify. An example is where I have 1 transmit antenna and 4 receive antennas. The concept of MRC is to combine all the ...
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Generating Octave Band Noise Spectra
So, I want to generate different spectrums of noise, in the 10 octave bands between 20hz and ~20,0000hz, in code. At first I was thinking of generating random numbers for white noise, then running ...
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main idea of Adaptive histogram equalization (AHE)
I want to understand the main idea behind AHE and the way for applying it manually with my hands.
Wikipedia says:
In its simplest form, each pixel is transformed based on the histogram of a square ...
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Mathematically show the problem of Histogram Equalization
Wikipedia - Adaptive Histogram Equalization says about classic Histogram Equalization:
This works well when the distribution of pixel values is similar throughout the image. However, when the image ...
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purpose of histogram equalization
What is the main purpose of histogram equalization on image? Is it used to enhance contrast of image or is its goal finding a transformation which gets a more
uniformly histogram?
Although Wikipedia ...
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MATLAB: cannot get CMA code for polarization demultiplexing to work
[ Edit: the CMA code seems to work after all, the problem is likely elsewhere (timing recovery), see added text at the end. ]
Yesterday I implemented some CMA code for polarization demultiplexing ...
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Is there any sampling offset when using external reference signal
I perform real experimental tests for optical communications using DCO-OFDM. The transmitted signal is uploaded into an AWG (arbitrary waveform generator), then bias (2.5 V) is added before adopting ...
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Can a LMS adaptive filter be adapted for MISO?
How would the LMS equalizer dimensions change for the MISO case?
LMS adaptive filters are typically described for equalizing a single input signal, $x(t)$. Can the LMS algorithm be modified in the ...
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Feedforward equalizer MMSE vs ZF: I get ZF performs better than MMSE, why is that?
So I am doing some experiments on comparing MMSE and ZF performance. Here is the description of my problem setup:
Consider a pulse response $p_{tilde}$ which is equal to:
[7.41283693728174e-06
-6....
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Can I still use match filter (eg.RCC)at rx when there is none at tx? Can it help with ISI?
As the transmitter is restricted to size and power considerations, there is no way to apply a SRRC filter at tx side. Can I just put a RC(raised cosine filter) at the rx side to alleviate ISI?
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Multi-path equalization in SERDES system analysis
In transmitter I send the data 1 sample per bit, then received in Rx passing by ADC then FFE adaptive filter and then a slicer to return the samples in bits and calculate the BER and it works well
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Group delay compensation for non coincident drivers
Suppose I have a two-way speakers system which can be modeled as a two-way Linkwitz-Riley crossovers network with impulse responses $h_{lp}(n)$ and $h_{hp}(n)$. I would like to equalize the group ...
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Pilot-based channel estimation in OFDM systems with fractional delays
Most studies on OFDM-based communication systems consider that multipath channels consists of a limited set of taps in the discrete-time domain. However, this only holds if the tap delay is a multiple ...
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How are the reflections in a quarter wavelength transformer dealt with in signal processing?
I haven't seen this issue ever explicitly discussed.
Briefly, reflections cannot be avoided in a quarter wave transformer due to the characteristic impedance not matching the source or the load. In ...
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Inverse of filtering and inverse of equalization
Is comb filtering a reversible operation? If applied to a signal, can I restore the original signal from the filtered image?
What about the histogram equalization operation? Is it reversible?
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Audio Equalization, Is Parallel or Cascade better
I'm not really an audiophile, so I can't determine the difference. I was playing around with Matlab's Graphic EQ and I noticed that there is a difference in the Magnitude response for the same gain ...
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Equalization in CAR- Automotive Audio
Can someone tell me what is the purpose of CAR Equalization in audio and why before CAR Equalization ,gain adjustments are necessary ?
Also why would someone use FIR filters during CAR Equalization ...
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What phase rotation occurs when you take the derivative of an audio signal?
If you take the derivative of an audio signal, it provides a 6 dB/oct upward sloping filter (increasing high frequencies / cutting low frequencies) all the way across the spectrum.
What is the result ...
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Upmixing after Equalization [duplicate]
Can anyone tell me why in a stereo mode many channels are derived from the 2 channel input . It looks like upmixing.. My questions are summarized below :
If it is Stereo mode why upmix it to many ...
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Equalizing audio under linux / Raspberry Pi
I have an audio streaming receiver written in Python running on a raspberry pi. This receiver writes the streamed audio out to an alsa device, which in turn passes it to an amplifier which is driving ...
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Peaking filter (loudness) cutoff frequency in an equalizer
An equalizer we have consists of Loudness ,Bass ,Mid and Treble .The loudness is nothing but a Peaking filter with cutoff frequency 20Hz .I read this in a book that outlines the EQ design.
I was ...
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Strange results with all pass compensation
I am new to DSP and, as a learning exercise, I am trying to design an all-pass filter in order to compensate the phase of an input impulse response (heqm.mat, which you can download from here).
The ...
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All-pass phase compensation only in a specific frequency range
I am trying to design an all-pass filter in order to compensate the phase distortion at the output of an equalizer. To do so, I take the phase vector of the output, compute the real and imaginary part ...
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Mathematical expression of Multicarrier frequency equalizer
I have a signal $X$ with length of $N$, multiplied with any unitary matrix, i.e the transpose of DCT matrix as:
$x = D' X$
where $D'$ is the transpose of the of DCT matrix. Then let's add $CP$ guard ...
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MATLAB model for equalizer using LMS algorithm adaptive filter and unexpected output curve
The MATLAB code below is for equalizer using lms algorithm adaptive filter and then plotting MSE (Mean Square Error) Vs Iteration numbers
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The cost function of LS algorithm
I'm trying to understand the derivation of LS algorithm for channel estimation in OFDM.
Could anyone explain why do we need complex conj transpose in the below equation?
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Compensating for poor illumination across a specific image axis - possible solutions?
A friend of mine is working at an institute for nano-membranes. Currently they are using ImageJ and do a lot of manual (in my opinion inaccurate) work to process some membrane "photos" (...
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Channel equalization affect on input signal
I have the following problem.
Am trying to understand how the channel block affects the input signal s(n).
I know that x(n), the input signal to the filter is basically:
\begin{equation}
x\left(n\...
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Zero padding OFDM equalization
In ZP-OFDM, The convolution is linear. it's different from CP-OFDM which is circular convolution leading to have one tap equalizer in frequency domain.
if I have a ZP-OFDM system, and we have a signal ...
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ZP-OFDM vs. CP-OFDM channel equalization
Now, I am working on OFDM equalization, according to what I understood, Adding CP into the OFDM block change the convolution from linear to circular. That circular convolution enables using point-wise ...
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Equalization of ultrasonic transducer [duplicate]
I am working with ultrasonic transducers with frequencies 100 kHz, one for transmission one for reception. The transmitted signals are chirps. I would like to measure the time of flight between ...
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Distortion of OFDM signal when using RRC filter
I am trying to transmit OFDM signal in pass-band based on RRC filter, but what I noticed that the signal before the RRC filter is completely different compared with signal after the RRC filter (It ...
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Should we upsample the channel when upsample the signal
I have an OFDM system with Number of sub-carriers $N= 1024$, modulated data using $QAM$ modulation is transmitted via those subcarriers as follows:
...
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Convolution that outputs a unit impulse
Im thinking whether any convolutional operation can output a unit impulse, an example to further explain:
where a convolution between system $h[n]$ and unknown system $g[n]$ would output $\delta[n]$.
...
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Time Reversal OFDM
I am trying to understand the Time Reversal OFDM where ,According to my opinion, the channel is reversed in time domain at receiver side and then equalized.
what I found online is something similar ...
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What's the computational complexity of MMSE equalizer in OFDM system
As I know that in case of one tap OFDM equalizer, (ZF equalizer), we should have $N$ division complexity since we divide every subcarriers by its correspondent channel tap in frequency domain.
But I ...
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How to implement Minimum mean-squared error (MMSE) equalization?
I have the channel estimation and noise power estimation and I need a matlab implementation of time domain siso channel Equalization.
Theory:
Consider the FIR filter of length $N+1:$
$$
\hat{s}_{k}...
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On the channel estimation based on vector
I have a matrix $X$ of size .i.e $(8,8)$ with $M$ columns and $N$ rows. Suppose I took it's $iFFT$ column wise resulting matrix $x$ of size $(8,8)$ too,
$x = F^HX_{(:,m)}, $ ...... (1),
where ...
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Is DFE equalizer always blind or can we use reference signal?
I have made a blind DFE Equalization, I mean decision directed .
But I am not sure how to make an implementation based on reference signal known by receiver and emitter. In the back forward filter ...
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How to use matlab toolbox for 2qam dfe equalizer?
I made Channel equalization with matlab,
You can find the code below.
...
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The use of LS estimation with Vector OFDM
I work in Vector OFDM, but I had an issue in channel estimation in that scheme. For example, I try to use LS channel estimation but I can't get the performance back. However, in conventional OFDM, I ...
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Channel estimation and interpolation by vector in OFDM
I have V-OFDM system (Vector OFDM) where every symbol is organized as in below figure:
The black cirles are pilots and white circles are data. First, iFFT operation it taken per column, and then ...
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OFDM time vs. frequency domain channel estimation/equalization
In OFDM, the majority of Equalizers are used in frequency domain. I mean the signal is transmitted in time domain (after performing iFFT), then to estimate the channel we should perform FFt to use ...
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Effect of Adding the cyclic prefix on the toeplitz matrix in OFDM
Assuming we have $N$ symbols to transmit encoded in block $k$,
Performing $N$−iFFT at the transmitter, we now have
The resulted signal $x(k)$ has length of $N$. inserting a cyclic prefix $CP$ ...
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MMSE- Channel estimated based - DFE Equalization
For HF ionospheric channels ( frequency range 3 up to 30 MHz), I Want to make channel equalization in time domain, using MMSE criterion. I have to do it using the channel estimation.
I have some ...
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Is MMSE equalizer necessary?
For observation $y$, channel coefficient $h$ and gaussian noise $w \sim \mathcal{CN}(0,\sigma^2)$,
$$y = hx + w \tag{1}$$
Note that for OFDM system, (1) is assumed channel input-ouput equation on ...
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Adaptive equalization vs inverse of transfer function
I have the following equalization problem as shown in the figure below:
Now I can compute the coefficients for my adaptive FIR filter c (dim(c) = N) the following:
$\mathbf{c_{opt}} = (\mathbf{H}^T\...
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Block CMA algorithm
The Constant Modulus Algorithm is a common equalization method which adapts at every sample in an attempt to give a filter which produces a fixed power output. Divergence/convergence of the CMA ...
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