Questions tagged [equalization]

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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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5 votes
2 answers
285 views

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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3 answers
142 views

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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Why histogram remapping is required?

Why in some applications, like biometric identification, applying histogram mapping to normal distribution after applying feature extraction (using wavelets for example) may increase the recognition ...
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2 answers
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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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-1 votes
1 answer
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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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1 answer
111 views

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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2 answers
535 views

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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1 answer
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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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1 vote
1 answer
214 views

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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1 vote
1 answer
86 views

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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1 answer
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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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2 votes
1 answer
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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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1 answer
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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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2 answers
142 views

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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1 answer
178 views

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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1 answer
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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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278 views

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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1 vote
1 answer
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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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1 vote
1 answer
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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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1 vote
1 answer
125 views

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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1 answer
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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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2 answers
271 views

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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1 answer
137 views

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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1 answer
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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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4 votes
0 answers
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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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2 votes
1 answer
185 views

Output of Zero-forcing equalizer doesn't match theoretical calculations

Let's say I have a sequence $x[n]$ (signal) and perform convolution with another sequence $h[n]$ (channel), so: $$ y[n] = h[n]*x[n] = \sum_{k}{h[k]x[n-k]} \leftrightarrow Y(z) = H(z)X(z) $$ I'm ...
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0 votes
2 answers
262 views

Types of equalizers

I can't get my mind around the different types of equalizers and the difference between some of them. I've been looking at different books unsuccessfully. So far, I have Wikipedia's list and this ...
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2 votes
4 answers
723 views

What Information Is Lost by Histogram Equalization?

I cannot think of a way to restore an original image after histogram equalization. But this latter seems to "enhance" (= increase contrast of) the image's details. What information is then lost by ...
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1 vote
1 answer
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Question about image equalization

Let $f$ be an $N \times M$-image and suppose that $g$ is its equalization. Question - Why the equalization does not change the objects, why a car on $f$ does not convert into a bus on $g$?. It is ...
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1 answer
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On the signal recovery in OFDM after estimation

Given a modulated signal X which is transmitted based on OFDM with N = 256 sub-carriers through channel ...
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0 answers
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Clip wav by PSD

I have the following two things. sequence_1: Sound file in the wave format. PSD_1: Some PSD (Power Spectral Density). I want that the PSD(sequence_1) < PSD_1 for all indices. How I think about ...
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1 vote
0 answers
30 views

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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2 votes
0 answers
19 views

How to exploit auditory masking to boost intelligibility

I am currently working on a dynamic equalizer to improve a synthesized voice's intelligibility in noisy environments. The current implementation of my algorithm simply applies a parametric EQ to the ...
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1 vote
1 answer
113 views

Training Fractionally Spaced Channel Estimator and Equalizer

If you are attempting least squares channel estimation with a fractionally spaced channel estimator, do you want the training sequence to also be fractionally spaced or symbol spaced? It looks like ...
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0 answers
98 views

Digital Communications block diagram question

I am new to digital communications and trying to understand the basic underlying concepts of digital comm systems. So far , studying the course , I have some questions which if anyone can answer would ...
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