In signal processing, a filter is a device or process that transforms a signal by selectively choosing specific frequencies and leaving others with appropriate gain or as it is.

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What are some example of applications for LTI systems

I'm giving a lecture on LTI systems. I encountered some questions: for a discrete LTI system H with impulse response h, is the system applied on signal x(t) equals x*h - normal discrete convolution ...
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48 views

How to visualize and understand Gabor filter using matlab

I am reading a paper, in which the author defines gabor kernels as : $$ \psi_{\mu,\nu}(x,y)=\frac{\lVert \mathbf{k}_{\mu,\nu} \rVert}{\sigma^{2}}\exp (-\frac{\lVert ...
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23 views

Filtering out unwanted square wave (Radio: DCS/DPL signal)

I've need to remove a DPL/DCS signal from a recording. Roughly speaking, a DCS signal is a low frequency (67.15Hz) square wave sent at the same time, over the same carrier, as speech. Because it is a ...
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62 views

What is wrong with this method of detecting the presence of a signal?

I am trying to decode Morse code from an audio (wav) file. Here is the technique I am using to detect the presence of the signal: I have a window of size (sampling_freq/tone), where tone is the ...
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46 views

Filtering a Morse code (CW, OOK) signal

I am building a morse code decoder in Python. I am using SciPy and Numpy for FFT, filter, etc. It is coming along ok, but the signal is noisy. I am extracting the dominant frequency from the FFT of ...
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55 views

Any way to compensate for fractional delay filter's weakness between taps?

A little background: I have an FPGA (running at 200MHz) that I am creating multipath events using buffers, all of that works. I take RF, mix down to IF, sample, make adjustments, out the DAC, and ...
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24 views

Parameters of standard audio channel filters

I want to do some simulations of speech recorded on microphones. In order to simulate the channel response, are there any standard (FIR) filter parameters available that I can use?
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53 views

Filter that is like low-pass filter but for intensity?

Is there a type of filter for processing spectrum data that will subtract spikes in intensity? I was thinking of something like a low-pass filter but that takes away data if the intensity is too high. ...
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43 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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45 views

Correlating two signals [duplicate]

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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33 views

Separating fast decaying signal from a slowly decaying signal

I have a discrete signal $x[n]$ which is exponentially decaying but the decay constant is not known. This signal is observed over a certain time period, say $T$. The only known detail about $x[n]$ is ...
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27 views

digital filter and epoch length

A reviewer has asked me to re-filter my data to remove baseline drift. Each sweep is 170ms sampled at 1000Hz and the reviewer wants it high-pass filtered at 0.5Hz. The original bandpass settings on ...
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74 views

Best way to inverse Hilbert on FPGA?

I have a real signal that is being sampled via ADC and passed to a Xilinx V6 FPGA. I then do a Hilbert transform on it using the FIR compiler core and get the complex signal (I and Q) to tweak the ...
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86 views

filtfilt giving unexpected results

I am trying to filter EEG signals using butterworth filter and filtfilt. I have gone through a lot of documentation and these 2 commands seem sufficient for filtering. However, the results are ...
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3answers
86 views

Does perceived ADC resolution, range and precision depend on fixed point format? What is the best way to deal with this for signal processing?

I am working on a system that is implementing a digital filter that was designed for another system that had an FPU and a 12bit ADC. The system that I am working on is using the same filter without an ...
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1answer
12 views

How to model the dispersion which introduces a modulation driver of EML?

I need to model the dispersion which introduces a modulation driver of EML, in matlab simulations. The parameters are: Lambda: 1310nm PAM4 power: Pmax = 1.09 mW Pmin = 0.13 mW Bandwidth = 56Gbps
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70 views

Why impulse response

Why do people calculate impulse response? Generally systems are designed after modelling the possible input signals and calculating the appropriate filters for the desired outputs. Where does impulse ...
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33 views

Difference between delayed down-converted signal and a down-converted delayed signal

I am having trouble understand what I think should be a pretty simple concept. Conceptually I can understand that a signal that has been down-converted, and then delayed in time is different than a ...
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73 views

Wiener Filters - Obtaining image and noise spectrum

We all know the famous Wiener Filter, $$G(\omega_1 , \omega_2)=\dfrac{H^*(\omega_1 , \omega_2)}{|H(\omega_1 , \omega_2)|^2 + \dfrac{N(\omega_1 , \omega_2)}{S(\omega_1 , \omega_2)}}$$ How to we use ...
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50 views

Filtering method that minimizes ringing in time domain, implementable in Python

I am acquiring data through an oscilloscope, which I am then filtering. I am doing all of this in Python. I need a bandpass filter with stop bands from 0 to .4MHz, and 4MHz and up. My pass band needs ...
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53 views

Masking the mains hum to improve anonymity

Today, a news blurb appeared that claimed that attackers could identify the location in which an audio record was taken by matching the mains hum to known data. Sadly, I fear that this might be ...
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2answers
52 views

Could multiple echo reflections be combined to improve signal to noise ratio?

I am working on a system processing ultrasonic echo reflection. The transmitter creates a short ultrasonic pulse and the receiver analyses the reflection. If I send two pulses (back to back or with ...
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15 views

After detection of veins, how to calculate the length of the particular veins as shown in the image?

This is a follow up question from this question. Please see this question for more details. I want to calculate the length of the veins as showing red circled in this below picture.
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84 views

Digitally undoing a hardware filter

I have a bunch of data that went through a hardware filter before being digitized. The data has been taken this way for quite some time, and everyone is fine with that. Now, there is a new application ...
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53 views

DSP Demodulation advice sought - please help

my field of engineering is condition monitoring. I use vibration analysis to determine the current state of health of a machine and then recommend any course of action required to ensure it does not ...
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48 views

About a filter's rise time

I have just a few questions regarding the rise time of filters. A rise time seems to be measured by using a step input, with an input typically from 0 to 1. However this is what I cannot seem to find ...
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48 views

deciphering the frequency response from the input data

Newbie to Signal processing, sorry if the question is basic. I have a data set consisting of 601 values. The values being time Vs voltage . The voltage values have transients in them. My aim is to ...
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54 views

FFT filter to remove cd scratch

I have a .wav file which came off of a cd with a scratch, so there is a periodic "clicking" of about 6 Hz. I was playing around with trying to squash the clicking by taking FFT and filtering the ...
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19 views

Is there two Types of Scale Space in SURF algorithm?

I couldn't figure out below paragraph on SURF paper and hope that someone can help me to understand it. Bay H., Ess A., Tuytelaars T. Van Gool L. - Speed-Up Robust Features (SURF), page 4, ...
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47 views

Applying Discrete Filters

I have an exercise in DSP. I learnt about discrete filter but I don't know how to apply it to produce an output from an input signal. Please guide me to do this: Assume fundamental sample time is ...
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10 views

Filtered backprojection implementatoin

I am wondering the detail of the filtered backprojection. Suppose I have a projection file: $p(s,\theta)$=[1 2 3 1 2] Then to get its filtered backprojection ...
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1answer
42 views

Parameters for signal analysis

I am extremely new to signal analysis. And before posting I did a lot of reading on signal analysis, FFT and windowing. I am working on my thesis which involves comparison of speech signals lets say ...
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93 views

How do I manually plot the frequency response of a bandpass Butterworth filter in MATLAB?

I have code like below that applies a bandpass filter onto a signal. I am quite a noob at DSP and I want to understand what is going on behind the scenes before I proceed. To do this, I want to know ...
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47 views

FIR-Decimation and Low-pass filter (taps vs number of input points vs number of decimation stages)

I am new to digital filters and trying to understand parameters behind them. Scenario I am trying to get DC value from signals sampled at 100kHz sampling rate. such high frequency is used due to ...
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1answer
86 views

How can I load a wav file, split it in frames, apply different filters do different frames and then recombine the filtered frames into a single file?

I'm working on a wav audio file using MATLAB. What i would like to do is: load a wav file and divide it into frames of the same dimension filter these frames (with a different filter for each ...
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1answer
32 views

extract the tree structure from a noise data set

I am currently doing a project that attempts to reconstruct the 3D structures from slices, i.e. the tomographic approach. After many steps of image processing, the last task is to connect the ...
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1answer
72 views

First-order low pass filter with bounded derivative

Given a function $x(t)$ and a first order low-pass filter $\frac{dy}{dt} = \frac{1}{\alpha} (x(t) - y(t))$, is there a way to choose $\alpha$ analytically such that the derivative of $y(t)$ is ...
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1answer
42 views

How to implement simple noise filter based on the frequency domain information?

Brief introduction: I am working on my university project. My task is to develop application that captures sound from mobile phone and removes/reduces noise (this simpilied version of task). I never ...
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1answer
87 views

MATLAB filter not attenuating enough

Currently, I'm working on removing 50 Hz power line interference from an ECG signal. Before trying out notch filters, I decided to try out a simple lowpass filter with a cutoff less than 50 Hz. Here's ...
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131 views

Allpass group delay formula and effect on Karplus-Strong

Some introductory questions: What is the unit of the group delay in a digital filter (is it samples?) What is $\Omega$ in the equations below (is it $\Omega=2 \pi\frac{f}{f_{sample}} ?) $ If I got ...
3
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403 views

Deconvolution by convolution

This is now a second time I am attempting to ask this very important but simple question here. What I want to know is can you do deconvolution by convolving a signal. It is often stated that, for ...
2
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1answer
68 views

Magnitude of gradient in frequency domain

I'm learning some basics of image processing. Recently I've read about image filtering and two-dimensional Fourier transform, because I'm preparing for exam. And I have one question I don't know ...
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1answer
51 views

How to detect a spiky signal embedded in a periodic signal

Say I've got a signal that I know is composed of periodic components. However, I'm worried that there are "spiky" events that are embedded in this signal, and potentially occurring periodically. I ...
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1answer
87 views

Implementations of Low-Pass Filter

I should say which of the filters from the following image implements an ideal low-pass filter with cutoff frequency $\frac{\pi}{4}$. In the picture, Sa is a zero insertion filter, which inserts a ...
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1answer
67 views

Is it possible to change sampling frequency of DSP kit if the sampling rate is fixed?

I am using a DSP kit TMS320c6711. It has a fixed sampling rate of 8000 samples per second. As I have to do real time filtering of frequencies above 5oHz with sharp cut off, I must reduce the sampling ...
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100 views

Causality of Linear Phase Filter

If a digital LTI filter has phase response on the form $arg[H(e^{jw})] = -\alpha\omega$, what could one say about it's causality (and consequently, the causality of it's impulse response)? Also is ...
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57 views

Autocorrelation of the product of deterministic and random signal

I was wondering how to calculate the autocorrelation of a deterministic signal $x(t)$ multiplied by a stochastic process $M(t)$, whose autocorellation $R_M(\tau)$ is known a priori. In my case, $x(t)$ ...
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41 views

Intuition behind the Gaussian Filter in Image Processing

I've been using a Gaussian Filter and know how to use it but I don't understand the physical significance behind using the filter. We use it but why? What is the significance? I'm just starting out in ...
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63 views

Which come first, PCA, FFT, filtering

Might be a simple question, but I keep second guessing my algorithm, so a confirmation would be good. I first do bandpass filtering, then PCA, then FFT of the top principle components. I also do some ...
2
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65 views

How to remove historical values from exponential filter

Suppose I have two time series $A:=[0,0,0,4,5,6]$ and $B:=[1,2,3,4,5,6]$. I implement the following filter (with initial value at the first element): $$ f(t) = f(t-1) + \alpha*(f(t)-f(t-1))$$ with ...