An adaptive filter is a filter that self-adjusts its transfer function according to an optimization algorithm driven by an error signal.

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Instability problem in NLMS adaptive algorithm

I have been used NLMS algorithm to equalize 4x4 MIMO signals, but the bit-error-rate (BER) after equalization is unstable with iterations. I don't know if it is the normal behavior of the adaptive ...
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44 views

Adaptive filter with two inputs

I have general theoretical questions: Is it true that an adaptive filter with two inputs (one normal and one delayed by the single time increment) can completely get rid of any single frequency ...
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51 views

LMS filter weight update

I have a general question regarding Least mean squares adaptive filters. Using the example of noise cancellation, I understand that if you have a set of reference signals (S) and corrupted signals (S+...
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2answers
54 views

What criteria should be used for smoothing

Actually I have some measurement which I want to get rid of noise I want to use different filter techniques but I am wondering what criteria I should use to check if I am removing noise or not or if ...
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33 views

Adaptive LMS(Least Mean Square) Equalization in OFDM

I have a problem with the adaptive LMS frequency domain equalization in OFDM. When I assume that the receiver knows the channel perfectly and apply zero forcing equalizer, there is no problem. Also ...
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31 views

Are the RLS filter and Kalman filter gradient methods?

I would like to extend my previous question What is difference between LMS and gradient-descent adaptation? with this other question. I found out, that RLS and Kalman filter learning seems to be ...
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28 views

Removing low frequency vibrations from measured signal

Suppose I have two sensors $s_1$ and $s_2$. $s_1$ measures the desired heart signal (with most of the frequency content below 100 Hz), and the other is a reference sensor picking mainly background ...
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1answer
48 views

Kalman for 3D position and 1D orientation

Is the following state correct for a Constant Acceleration (CA) model KF applied for tracking an object which moves in (x, y, z) and have the freedom of rotation $\phi$ around the $z$ axis? \begin{...
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65 views

What is difference between LMS and gradient-descent adaptation?

I found algorithms that seems the same to me, but they are described with different names (in field of adaptive filtering). For example: LMS - least-mean-squares seems to be GD - stochastic ...
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1answer
53 views

Best DSP algoritms for ultrasonic background noise cancellation

I am looking into detection of pressurized gas leaks by means of the broadband hissing sound (white noise) generated from pressurized leaking gas. The instrument will have a broadband microphone ...
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1answer
46 views

What is an Adaptive Mean Filter?

$$\hat f(x, y) = g(x, y)-\frac{\sigma_n^2}{\sigma_L^2}\left[g(x, y)-m_L\right]$$ What are the meanings of the following terms: $m_L$ ${\sigma_\eta}^2$ ${\sigma_L}^2$ Here we see that $m_L$ is ...
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21 views

RLS Algorithm Convergence

I am looking for some help to understand the concept how RLS converges? If possible to present it graphically that would be best. It is very easy to understand the understanding of convergence in case ...
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1answer
63 views

MATLAB Adaptive Filters

In the audio domain, I am currently attempting to use MATLAB to distil: $\textrm{signal}$ from $\textrm{noise + signal}$ $\textrm{noise}$ from $\textrm{noise + signal}$ using two adaptive filters $\...
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59 views

How to subtract one signal from another?

I am capturing some body internal signals. I am using 2 identical mics. One captures the in body signal and one open air. I want to remove/delete/subtract the open air signal (noise for me) from the ...
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1answer
48 views

Noise cancellation for known sources

Creating a noise cancelling earphones that cancel/suppress speech is a huge challenge , maybe even impossible. But what happens if we change the goals a bit: We need to cancel the noise(music,...
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60 views

Channel Estimation / Equalization - Estimate Channel Inverse Using White Noise Statistics Only

Given the system defined in the following figure: We have a system $ G \left( f \right) $ which is unknown yet can be defined by $ {N}_{p} $ poles and $ {N}_{z} $ zeros. The signal $ x \left( t \...
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20 views

How do you select an optimal adaptive filter length?

Is it a trial and error process or can you observe the minimum number of taps after which the impulse response reaches a steady state?
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23 views

How is it determined that an adaptive filter has converged?

Is it when the cost function such as the error signal or Mean Square Error (MSE) signal is minimised?
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2answers
50 views

Eigenvalues of a vector

I'm trying to calculate (with Matlab) the minimal and maximal Eigenvalues $\lambda_{min}$ and $\lambda_{max}$ of the autocorrelationmatrix $R$ to adjust the stepsize of an adaptive filter. My input ...
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59 views

Performance of adaptive filter

I have designed an adaptive filter for noise cancellation. Is there any standard way of testing adaptive filters?
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137 views

How many samples per cycle(time period) is actually enough to reproduce the sine wave sound properly?

I have been working on Active Noise Cancellation in real time for Air vent in kitchen. Initially for the demonstration purpose, I am using sinusoidal sound ( 40k Hz Fs,1000 samples, 2 kHz frequency, 1 ...
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1answer
36 views

Terminologies: Adaptive, recursive and iterative

Considering non-linear filtering technique like Extended Kalman filtering with Expectation Maximization (EM). EM is an iterative technique but what is Kalman filtering? Is Kalman Filtering called ...
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1answer
72 views

Echo cancellation supporting long delays and without frequency domain processing

AEC algorithms mostly rely on LMS adaptive filtering, i.e. you update FIR filter coefficients then perform the filtering. Theoretically, the FIR must be as long as the maximum echo length you want to ...
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1answer
46 views

LMS adaptive filter relatively delayed signal and reference inputs

I'm using two microcontrollers to implement an adaptive LMS filter to filter out the noise from the signal. One is recording the noise and streaming the data to the other microcontroller which is ...
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75 views

Audio block-processing discontinuities

I have an algorithm that looks at an audio frame, calculates a threshold in db-rms, and decides to filter the frame whether or not the threshold is crossed. However, filtering each block is producing ...
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51 views

FIR adaptive filter without reference input

Now I am trying to design FIR adaptive filter for unknown frequency CW rejection. I've already read many books or paper about 'adaptive noise canceling'. However I couldn't find any information for ...
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1answer
125 views

Help in deriving the update rule for equalizer

Considering an FIR system excited by an input $s_n$. If the input is derived from a mapping, and a +1/-1 BPSK signal is derived. Considering the Constant Modulus Algorithm (CMA). The channel is ...
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610 views

MATLAB : Proper estimation of weights and how to calculate MSE for QPSK signal for Constant Modulus Algorithm

I had asked conceptual Question about Constant Modulus Algorithm. I am implementing the simple steps of the algorithm, as I do not have the cma() built in module. ...
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38 views

Adaptive Filter Gradient Descent

The quadratic performance surface of an adaptive filter is a paraboloid. Its minimum can be found wherever the gradient is zero. However, since there are two types of paraboloids (elliptical and ...
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97 views

Motion artifact cancellation from ECG signal using 3-axis accelerometer data

I have a ECG signal measured as a test subject is performing 3 different activities - sitting, walking(2mph) and jogging(5mph) and also the corresponding 3-axis accelerometer(X,Y and Z) signals. I can ...
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1answer
64 views

Adaptive Digital Filter Block Diagram Question

I'm currently attempting to study up on adaptive digital filters. My book presents the diagram I've included below and I'm having trouble understanding conceptually what it's indicating. The problem ...
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1answer
71 views

Unit delay operator as parameter in function

I'm busy trying to implement a filter from this paper. I'm a bit confused with one particular step (30e in the paper). Basically I need to find the zero frequency gain (K) of the following whitening/...
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1answer
80 views

Filter to speed up convergence of geometric series

I want to speed up convergence of geometric series $\ \ lim + c^n \ \ $ where $|c| < 1$ and $lim$ is not known. A basic low-pass filter, here Butterworth, is good for $-1 < c < 0$ but not $0 ...
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1answer
79 views

Changing the cutoff of an IIR lowpass filter with minimal transients?

I have a 1st order lowpass IIR filter of the form $ H(z) = \frac{b_{0} +b_{1} z^{-1}}{1+a_{1} z^{-1}} $ implemented using the direct method my code looks something like this ...
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221 views

Questions about Active Noise Cancellation

Being new to ANC, this is my understanding of how ANC works: Ambient noise (n) is entering a geographically small zone. To suppress the noise, an interfering (corrective) sound is injected ...
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129 views

Is there a widely available implementation of an adaptive, recursive, numerically stable IIR filter?

I need to identify the coefficients of a linear, causal, time-invariant physical system that can be described by a classical state-space formulation. For the sake of the example, suppose that the ...
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3answers
242 views

Picking out a signal that appears to be noise inside a large signal

I have a signal from a photodiode sensor that has two types of noise. One type of noise is ambient light white noise that gets introduced just from the surrounding environemnt. The other type of noise ...
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2answers
39 views

variable length no-refrence filter algorithm

I'm searching for a an algorithm or an idea of implementation. I need to filter a signal in real time, and want to change the length of it (number of taps) in order to change the delay. In low ...
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1answer
217 views

Adaptive equalizer for IIR channel?

I am quite new to the idea of equalization. I have a few queries regarding the same. In my application I require to equalize a channel whose impulse response is an IIR response. Is it possible to ...
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185 views

Phase noise estimation and compensation schemes

Brief background There is a known problem that high order modulation schemes suffers from phase noise of reference generator. It's very important issue for e.g. line-of-sight (LOS) modems exploiting ...
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1answer
814 views

What is the difference between the Weiner-Hopf equation and the normal equation?

In adaptive filters, the development of LMS algorithm typically starts from the Weiner-Hopf equation, while the development of RLS algorithm starts from the normal equation. As I understand, these ...
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88 views

Adaptive filter weight adjustment

I have 3 sensor inputs: $a(t)$, $b(t)$ and $c(t)$. I want to design a filter such that the weighted linear combination of the three is always a constant. Kind of like: $$w_1(t)a(t) + w_2(t)b(t) + w_3(...
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2answers
504 views

Image Processing: Flatten a 3D Ball

There are many descriptions of how to turn a 2D image into a 3D one, however I want to do the opposite, in particular to a ball. As an example, consider the following ball: If only the (relatively) ...
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1answer
307 views

Correlating accelerometer data

I am getting a signal from a device. This signal contains a non-random noise signal in it. I want to remove that noise from the signal. This noise is correlated to the motion the device is having. So ...
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1answer
39 views

Deep zeros in the spectrum of the input data?

I wanted to know the meaning of "deep zeros" in the spectrum of the input data. I came across this terminology while going through the introduction of chapter 2 (Bussgang techniques for blind ...
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285 views

Using a Wiener Filter to Estimate a Transfer Function

As a follow-on to this question about estimating a transfer function of an unknown system using a Wiener filter, How would you put a minimum MSE criteria on how well the estimated filter weights ...
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346 views

AEC Speex . How does it work?

I'm working with AEC of Speex. The algorithm is based on the MDF adaptive filter + an adaptive learning rate. I'm using it like a ANC and it works very well. Does anybody have some material, as block ...
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1answer
93 views

Correction of a signal through a transmitter

I am inquiring as to a practical way to solve a problem I have. Basically, I need to transmit a signal, $x[n]$, through a seismic transmitter. (It will go through a D/A, etc). The transmitter that ...
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2answers
932 views

scipy.signal.wiener for audio processing

Does some have an example of what a Wiener filter (that can be used directly with scipy.signal.wiener) can be useful for, in sound processing (it seems that such ...