Questions tagged [filtering]

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1answer
568 views

Image zoom out using Gaussian blur and downsampling

I am trying to implement a simple zoom out algorithm using two steps: The image is blurred using gaussian convolution of standard deviation $0.8\sqrt{{\tt zoomfactor}^2-1}$ as we saw in class. The ...
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1answer
1k views

How to perform a gaussian blur using FFT?

I am trying to implement a gaussian filter with matlab.Here is my implementation: So far All I get as output is a black image. Any hints? ...
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1answer
50 views

Buffering block and filter length in real-time processing

I have a signal sampled at 256 Hz, which I want to filter with a 50 taps long FIR filter in real time. Would it be a problem, if my data block size is only 32 samples? And should I then concatenate 3 ...
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1answer
403 views

Filter problems in python

I am recording a 30 second 1000Hz Sine wave, saving it to a list, splitting the list into 5 second sublists and I would like to apply a notch filter to each sublist to check when the signal drops out ...
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2answers
236 views

Filter Implementation

I am rather new to the world of signal processing, and am struggling to understand a fundamental concept: How are filters actually implemented? I have read a significant portion of this online book, ...
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0answers
156 views

Electromyography: is this interference from the heart/how to remove it?

I'm using electromyography to evaluate the activity of lumbar erector spinae at various levels of effort. For this I also intend to sample the activity at complete rest (in prone lying). In my first ...
2
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1answer
3k views

homomorphic filter - python overflow

I'm trying to implement the homomorphic filtering as implemented by this research article - step 4 (pdf) The original Matlab code, which I'm trying to translate into Python, is as follows (WARNING: ...
2
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1answer
311 views

Denoising short, non-uniformly spaced, bandlmited sequences

Consider a bandlimited signal $x(t)$ with bandwidth $BW$. Samples of this signal are observed at non-uniformly spaced sample points in the presence of noise: $y(t_i)=x(t_i) + n_i \qquad i\in\{0,1,\...
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0answers
38 views

Multitapering in time domain to obtain smoother filtered signals?

Suppose we want to approximate the instantaneous power $z(n) = |y(n)|^2$ of the discrete-time signal $y(n)$, where $y(n)$ is the result of filtering $x(n)$ with a given window $h(n)$, $y(n) = x(n) \...
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1answer
3k views

Does Higher Sampling Rate Increase SNR?

I have AM demodulated voice samples that come from a 14bit ADC that I will filter, process, and then send to a CODEC. I can choose a sample rate of 96kSPS, 64kSPS, 48kSPS, or 32kSPS at the CODEC. ...
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0answers
259 views

How to include phase noise in sinusoidal kalman filter model?

I am modelling simple sinusoidal motion using a Kalman filter from the following equation of motion: $ \ddot{x} = -\omega^2x $ So my matrix equation of motion is: $$ \begin{bmatrix} \dot{x} \\ \...
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2answers
89 views

Tracking unknown number of signals/coordinates

I have a time series data. Where for every time step I have a varying number of object coordinates. I want to track these over time. There might also be some missing coordinates for a few frames. ...
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1answer
45 views

Is this a robust method for analysing correctness of a filtered signal? Is there a more robust method?

I have a recorded signal which contains several frequency components with stochastic phase and amplitude changes and want to extract the true signal with the other frequency components and noise ...
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1answer
821 views

How can i create a low pass filter in matlab

i am trying to create a low pass filter in matlab for a project in signals and systems class but i couldn't. cut off frequency is 500 , sampling frequency is 10000 and the low pass filter's band width ...
2
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0answers
40 views

Filtering for Wright-Fisher HMM

I am trying to understand what filter may be suitable for the following HMM: The signal is a Wright-Fisher one-dimensional diffusion characterised by the SDE $$dX_{t}=\frac{1}{2}\left(\alpha(1-x)-\...
2
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1answer
155 views

Standard deviation is varying with change in amplitude of DC signal

I am trying to make sense of the below code. I am taking a large sample so that I get good estimates for standard deviation. ...
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0answers
94 views

Fastest way to subtract known music tracks from live videogame audio stream

I want to isolate video game "action" sounds from the video game soundtrack. Given all ~20 songs, I'd like to filter them out from any live audio stream during gameplay. What is a fast and robust way ...
1
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1answer
7k views

Differences between low-pass, band-pass, notch filters

I'm studying image processing and I know that there are different filters you can apply. I don't understand the difference between the low-pass/bandpass/notch filter (or high-pass/band-reject/notch). ...
4
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1answer
7k views

Simple software low pass filter

I am measuring voltages and currents of a 3-phase electrical machine and I need to calculate the power. Every interrupt (frequency between 30-70kHz) I get values (voltages, currents) from analogue-...
0
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1answer
312 views

Relative Computational Complexity for Channelizer Implementations

Suppose I want to separate a broadband input signal into multiple narrow subbands using an FFT-based analysis filter bank. The filter bank uses a prototype lowpass filter and is implemented using a ...
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1answer
98 views

Filter results from force measurements

I was provided with several force measurements. Precisely: The vertical compression force exerted from the milling tool on a working peace. The plot of the force looks reasonable and of course it ...
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4answers
2k views

Does a filter add oscillations to a signal?

this is a more general version of a question which i asked previously. From what I understand, the purpose of a filter is to change the amplitude of a specific frequency band. As I went through the ...
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1answer
348 views

How to find analytic description of filtered signal

I am looking for an exact analytic description of a filtered signal. I have an electronic circuit whose input is a monoexponential decay. First (1) the signal gets filtered by a simple RC-Lowpass. ...
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2answers
3k views

How to apply low-pass filter to an I/Q signal to get baseband signal?

Can anyone help me with the demodulation technique of a modulated signal? I mixed it with I/Q signal. But I am very confused about low-pass filtering. I am trying to apply a low-pass filter, but I am ...
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1answer
692 views

Digital Lowpass butterworth filter with cut off 500Hz and sampling rate 1.25MSPS

I am trying to simulate a distributed sensing system and I need to filter only frequencies lesser than 500 Hz(low pass filter) from acquired signal with sample rate 1250000 Samples/sec using below ...
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1answer
1k views

Adaptive filtering: Optimum filter length and delay

I'm trying to find the optimum filter length for an Adaptive Filtering, using RLS Algorithm. I'm using this design: So the "error" signal is the signal without noise (and that's the signal that I ...
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2answers
3k views

preprocessing raw ECG data

I need to preprocess raw ecg data in R, here is a sample already standardized. I'm not an expert in signal processing nor experienced in working with medical data, so I need concrete answers ideally ...
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2answers
483 views

Optimal Level of Wavelet Decomposition for Denoising

If a certain mother wavelet is defined and the optimal threshold shall be defined via Donoho, how can I define the optimal decomposition level to achieve the best denoising results.
1
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1answer
546 views

Analytical expression for step response of digital bessel filter

If I apply a digital Bessel filter to a perfect step function, I get something that looks like the following: The green line is the input step response data sampled at 500kHz, the red line is ...
1
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1answer
481 views

Bandpass filtering an audio signal with MATLAB's $\tt kaiserord$: unknown new frequency component

I am trying to filter an audio signal with kaiserord in MATLAB, but I'm having a problem. Here is my code: ...
0
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1answer
184 views

Extracting narrow-band ZigBee signals(4 MHz) from a wide-band WiFi signal(20 MHz)?

I am planning the following. First sample the 20 MHz WiFi channel (WiFi channel-1 in figure). Put band pass filters (5 MHz wide) around each of the ZigBee center frequencies (11, 12, 13, 14). Re-...
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3answers
2k views

How do I eliminate line noise from USB microphone

I'm trying to record voice from a microphone into my laptop. Unfortunately, the laptop does not have a microphone jack, so I have to use the USB input. This doesn't present a problem when I record ...
1
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4answers
298 views

Understanding the lowpass filtering of a digital signal

I do not have any background in Electrical Engineering and I have recently started a project which involves signals captured from sensors. Lowpass filtering: The way I understand it is: The values ...
2
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3answers
154 views

How to filter key clicks?

I am the author of an amateur radio application that produces a waterfall display across a range of frequencies. Time is on the $x$-axis, frequency is on the $y$-axis, and the relative strength of ...
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1answer
3k views

How do we use signal::filter and signal::butter in R for EEG data?

I am trying to design an experiment to determine the peak amplitude of an EEG signal in response to a stimulus. Till now, our team has been using MATLAB and since we wish to go open source, we are ...
2
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1answer
3k views

What is the significance of Butterworth filter in image processing?

Filters like mean,median,gaussian,bilateral and adaptive forms of these filters are used commonly in image processing but not Butterworth filter. The reasons I could think of are a) Butterworth ...
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2answers
162 views

How is Bayesian Estimation related to filtering?

I am reading about estimation theory, including topics like Bayesian Estimation (e.g. Wiener Filtering). It seems that we usually define a filter in terms of tis frequency response (e.g. High Pass, ...
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2answers
854 views

Practical examples of ARMA model

I am studying the Kalman filter and its basic implementation, and it was asked to use the filter to estimate a signal observed in noise $$y(n) = x(n) + v(n)$$ where $v(n) \sim \mathcal{N}(0, \sigma^2)$...
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0answers
293 views

Prediction-error filter for images

I am interested in studying local pixel value dependencies in images and I am wondering if it exists a general form of prediction-error convolutional filter that is able to suppress the image's ...
3
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1answer
680 views

Wiener filter to estimate constant signal

I want to compare the performance of a Wiener Filter and the Kalman filer to estimate the value of a constant $d$ using mesurements corrupted by a white noise. That is, my measurements are of the form ...
3
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1answer
2k views

Interpolating/Decimating CIC Filter Group Delay

I have an Interpolating Cascaded Integrator Comb (CIC) filter designed as so: Rate Change = 100 Number of Stages = 4 Differential Delay = 1 I'd like to calculate ...
2
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2answers
144 views

Equalizing frequency response in software

I'm playing audio through a speaker which I know to have a non-flat frequency response, with particularly poor response in the low ($<1\textrm{ kHz}$) ranges. My plan to get around this problem is ...
3
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2answers
272 views

Easy way to get rid of noise in a hand drawing

I would like to take a user's hand drawn input, and filter out "noise", aka small sketches or blobs, where the user might have screwed up and accidentally touched his hand to the drawing device, or ...
0
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1answer
774 views

Filter and crop an image

I am a big fan of fft convolution. So, I mostly try to avoid non-fft convolution. Suppose, I am trying to convolute an image with another image. Suppose the first image is $512\times 512$, and, the ...
2
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2answers
1k views

Smoothing a staircase

I have some data from a position encoder, so naturally i want to estimate its speed. However, the data is very quantized, so it's difficult to smooth enough to differentiate easily: Each step level ...
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0answers
35 views

How do I smooth-over transition from a time-series generated by one system to a time-series generated by another system?

So I have generated a time-series with length on 2N samples, where the first N are generated by one auto-regressive system and the N+1 to 2N are generated by another, similar, auto-regressive system. ...
2
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2answers
4k views

Root mean square bandwidth of a signal with flat spectrum

I am trying to derive a simple expression for root-mean-square bandwidth $B_{\rm rms}$ for a signal that has flat spectral density over its entire bandwidth $B$. The expression for the $B_{\rm rms}$ ...
1
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2answers
773 views

Convolution to do FIR with initial and final conditions!

I need to apply an FIR filter on chunks of very long signals. I can use MATLAB's filter function as follows to preserve the state of the filter when a new chunk of data is available: ...
1
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1answer
264 views

Shock filtering using structure tensor

my name is niladri, I am new to image processing(actually this is my first code). I want to implement shock filter using structure tensor. I have rough idea of what structure tensor is and implemented ...
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1answer
2k views

Smoothing a power spectrum

My question is regarding how one could/should smooth a rather noisy power spectrum obtained from measurements. There are various methods one can use (a moving average, binning, etc) and I am not sure ...