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8 votes

do digital equalizers use Fourier transforms?

Fourier transform technology Well, Fourier theory is behind every kind of equalizer. We wouldn't know what "equal" means without; the Fourier transform is how we know how to describe a ...
Marcus Müller's user avatar
5 votes
Accepted

OFDM time vs. frequency domain channel estimation/equalization

Traditionally, OFDM became popular in WiFi and LTE because the channel model consisted of multi-path. That is, the radio signal transmitted in 1-6GHz frequencies bounced from various obstacles (walls, ...
jithin's user avatar
  • 2,263
5 votes
Accepted

Group delay compensation for non coincident drivers

For the first question, given the linear process, what you do to the sum with regards to filtering is equivalent to what you do to each and then sum. For the second question, the dip is in the ...
Dan Boschen's user avatar
  • 52.4k
5 votes

Why do inverted impulse responses sound awful when applied to an audio system?

For simplicity we assume that the room and the source are fixed. A room's impulse response depends on a LOT of different factors which include the exact position, directivity and orientation of the ...
Hilmar's user avatar
  • 45.7k
5 votes

Least Squares Solution Using the DFT vs Wiener-Hopf Equations

Following Royi's derivation, we want to show that, $$\begin{align} \hat{h} = \arg \min_h||Xh - y||^2 = (X^T X)^{-1} X^H y = IDFT(Y \oslash X) \end{align}$$ where $X$ is a circular convolution matrix ...
orchi_d's user avatar
  • 587
4 votes
Accepted

What is the difference between an equalizer and a channel estimator?

In communication systems, transmitted signals are distorted by the physical medium (the channel) charactheristics. The channel estimator tries to identify the transmission channel characteristics, by ...
Fat32's user avatar
  • 28.3k
4 votes

Group delay compensation for non coincident drivers

I'm not sure whether this is a purely academic exercise or supposed to do something useful in the real world. Assuming it's the later, there are a few additional points to consider Typically when ...
Hilmar's user avatar
  • 45.7k
3 votes
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Histogram Equalization

Assuming that in your question $T(r)$ denotes a map $:\mathbb{R}\to[0,1]$ and assuming that it is continuous and strictly increasing, then it is obviously an isomorphism among $r\in[0,1]$ onto its ...
LJSilver's user avatar
  • 768
3 votes

Remove a frequency and all its multiple (harmonics)

The choice of algorithm depends on your application scenario - i.e. there is no best solution per se. If your focus is on minimum computational requirements, a comb filter will probably be optimum. If ...
applesoup's user avatar
  • 647
3 votes

CMA Equaliser and FSK

The confusion comes from the fact that what is tagged as "transmitted" isn't the real transmitted waveform but its baseband representation, which are $\left\{+1,-1\right\}$ symbols in 1 dimension. For ...
SleuthEye's user avatar
  • 1,792
3 votes

Why do the OFDM training (and payload) symbols have silent sub-carriers (aka virtual carriers)?

From the first to the sixth OFDM-Symbol you have spread virtual carriers equally across [0,..,51] with a distance of 3. With this way you have spread your 'energy' loss over a wide spectrum. In ...
Andrej Rode's user avatar
3 votes
Accepted

What is the difference between pulse shaping and equalizers when used to cancel Inter-symbol Interference (ISI)?

1. This is a question investigated by many researchers decades ago. They discovered that the bandwidth limitation of R/2 Hz is not a fundamental limit set by nature. It is just a criterion if we don't ...
QMC's user avatar
  • 784
3 votes
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how to set Equalizer's coefficient using generalized eigenvector.

The generalized eigenvalue problem is given by $$Bw=\lambda Cw\tag{1}$$ where $\lambda$ is the generalized eigenvalue of the matrices $B$ and $C$. Multiplying $(1)$ from the left with $w^H$ (with $^...
Matt L.'s user avatar
  • 90.5k
3 votes
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Adaptive equalization vs inverse of transfer function

Inverting a channel can only be done when the channel is a minimum phase system (trailing echos only). A minimum phase system is characterized as having all zeros in the left half plane (for the s ...
Dan Boschen's user avatar
  • 52.4k
3 votes
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The use of LS estimation with Vector OFDM

Sorry for late reply .. I was little bit busy. you have mistakes in your code. Although mythology is right, you have mistakes in some parameters. Check this paper "Low-Complexity Equalization of ...
Zeyad_Zeyad's user avatar
  • 1,056
3 votes
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Distortion of OFDM signal when using RRC filter

I checked your code in my PC, you need just to delete the delay added before the filter. For example, you can use: U_aft_fil = U_aft_fil(fil_delay+1:end); Then ...
Zeyad_Zeyad's user avatar
  • 1,056
3 votes
Accepted

How are the reflections in a quarter wavelength transformer dealt with in signal processing?

The OP clarified in comments that his real question/concern is with the transient response of the reflections that occur in a 1/4 wavelength transformer. In any typical application given the ...
Dan Boschen's user avatar
  • 52.4k
3 votes

Why construct a minimum phase filter from measurements?

Room Equalization for listening purposes is NOT the same as equalization for, say, acoustic echo cancellation or data transmission purposes. Inverting the measured impulse response or transfer ...
Hilmar's user avatar
  • 45.7k
3 votes

Why do inverted impulse responses sound awful when applied to an audio system?

One thing that I remember from a Brüel & Kjær application note from the 1980s or 90s is that for a room impulse response, you wanna separate the frequency response (and therefore the impulse ...
robert bristow-johnson's user avatar
3 votes
Accepted

Group delay equalization for second order IIR notch filter

Yes if you have access to Matlab's arbitrary magnitude and phase tool, that is certainly a good bet. Other approaches if you want to get more into the design details are: As an IIR solution, see the ...
Dan Boschen's user avatar
  • 52.4k
2 votes

Fractional spaced equalizer + timing (clock) recovery

The answer is to NOT down-select to one sample per symbol until after using the Gardner Timing recovery since the TED requires 2 samples per symbol. If the equalizer is running at 2 samples per symbol,...
Dan Boschen's user avatar
  • 52.4k
2 votes
Accepted

MP3 equalization

The usual approach to achieve your goal would indeed consist in decoding the MP3 file to a series of uncompressed time-domain samples and then filtering this PCM signal. As you are building a player, ...
applesoup's user avatar
  • 647
2 votes

Equalizing frequency response in software

Whilst I am not well versed in Scipy, or how the firwin2 function works that you have quoted, this is a very complicated problem that you propose, and there is a lot more to think about than you may ...
MDT's user avatar
  • 53
2 votes
Accepted

How to equalize an ISI channel when the transmitted symbols are unknown?

The classic approach is to include a "training sequence" along with the data. The training sequence is known to both transmitter and receiver, so it can play the role of $\mathbf{x}$ in your question. ...
MBaz's user avatar
  • 15.3k
2 votes
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spectral factorization method

The question is not so clear. I am not sure what other types of examples you consider. In this particular case, if you didn't get the hint notice that: $$\begin{align} c(1+\alpha D)(1+\alpha D^{-1}) &...
msm's user avatar
  • 4,295
2 votes

What Is the Difference between RLS, LMS and Wiener Filter? When Is One Preferred Over Another?

All three are Estimators / Predictors. All of them try to estimate the coefficients of Linear Filter which minimizes an MMSE Cost Function. The Wiener filter assumes all data is given and sets the ...
Royi's user avatar
  • 19.9k
2 votes
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Constant modulus algorithm - performance poor?

The constant modulus algorithm does not work for QAM because the amplitude of QAM at the symbol decisions is not constant (therefore not a constant modulus signal), such as BPSK and QPSK. SIR is the &...
Dan Boschen's user avatar
  • 52.4k
2 votes

Magnetometer coil equalization

I would equalize both channels. The most robust method is to cut both back to a lower bandwidth. Then you only need to equalize the gains. Assuming that your scanning by hand a 1-2 second sweep rate ...
rrogers's user avatar
  • 425
2 votes
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Determining pulse shape for Viterbi Equalization

I'll answer my own question with what I've learned in the past 28 days. Hopefully I've got it right! Viterbi equalization is just one way to equalize the channel, as an alternative to some other ...
Phil Frost's user avatar
2 votes
Accepted

Precursor ISI - causality violation?

Every symbol in the channel will be affected by ISI from previous symbols and next symbols. To understand this you must notice that there's a propagation delay from transmitter(TX) to receiver(RX). ...
VMMF's user avatar
  • 1,142

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