8
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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 ...
- 32.5k
5
votes
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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, ...
- 2,303
5
votes
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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 ...
- 55k
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 ...
- 48.2k
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 ...
- 647
4
votes
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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 ...
- 28.4k
4
votes
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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 ...
- 55k
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 ...
- 48.2k
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 $^...
- 92.5k
3
votes
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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 ...
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3
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 ...
- 20.5k
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 ...
- 1,802
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 ...
- 55k
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 ...
- 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 ...
- 1,056
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 ...
- 48.2k
3
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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 ...
- 21.5k
3
votes
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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 ...
- 55k
2
votes
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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.
...
- 15.4k
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,...
- 55k
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 &...
- 55k
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 ...
- 425
2
votes
Inter Symbol Interference (ISI) / Equalization in Digital Signal Processing
If the channel just adds noise and does not cause any distortion (as in the first figure), you can design the transmit filter $g(t)$ such that, when combined with its matched filter at the receiver, ...
- 92.5k
2
votes
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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). ...
- 1,182
2
votes
estimate the impulse response after equalization
Note that what you're trying to do is equalization, as opposed to channel estimation. If we ignore the noise for the moment then, ideally, the concatenation of the equalizer and the channel (modeled ...
- 92.5k
2
votes
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Is the Channel shortening similar to Time domain Equalizer (TEQ)
Most likely people use different words to describe the same concept. This happens quite often. The TEQ is the more general term and also used to equalize other methods that OFDM, while CS is related ...
- 1,056
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}) &...
- 4,315
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 ...
- 417
2
votes
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Where in the signal chain is Channel Equalization applied?
Generally, any matched filtering would be done before equalization, since there is no practical advantage that I am aware of to applying a matched filter afterwards. Most textbooks that I've read ...
2
votes
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Training Fractionally Spaced Channel Estimator and Equalizer
The training sequence should be at the same spacing as the equalizer when considering its sampling at the input to the equalizer. Adaptive algorithms converge to the least square solution based on the ...
- 55k
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