Signal Processing Stack Exchange
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1500 questions
14
votes
1 answer

Why is $y(n) = x(n) + x(n-1)$ a low pass filter?

I have found that this is a simple, but bad lowpass filter: $$y(n) = x(n) + x(n-1)$$ However, I can't understand why it is a lowpass filter. What is its cutoff frequency?
GorillaApe
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2 answers

When should I calculate PSD instead of plain FFT magnitude spectrum?

I have a thirty-second speech signal that was sampled at 44.1 kHz. Now, I would like to show what frequencies the speech has. However, I'm not sure what would be the best way to do that. It seems sometimes one calculates the absolute value of a…
spede
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Given Position Measurements, How to Estimate Velocity and Acceleration

This is simple i thought, but my naive approach led to a very noisy result. I have this sample times and positions in a file named t_angle.txt: 0.768 -166.099892 0.837 -165.994148 0.898 -165.670052 0.958 -165.138245 1.025 -164.381218 1.084…
lgwest
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3 answers

FFT for a specific frequency range.

I would like to convert a signal to frequency domain. The desired frequency range is 0.1 Hz to 1 Hz and the frequency resolution is 0.01 Hz. With the sampling rate of 30 Hz, FFT gives the frequency components up to 15 Hz. Raising the sampling rate…
NcJie
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13
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4 answers

Why is the time domain low-pass filter the "sinc" shape?

Consider: I'm looking at low-pass filters, and I see that the time domain representation of an "ideal" filter resembles the shape above whereas the frequency domain is a box. I also get the as you lower the cutoff, the main lobe in the middle gets…
thepman
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13
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1 answer

How to perform carrier phase recovery in software?

What are the options for recovering the phase of a BPSK signal in software? The only resources I can find online contain circuit diagrams – there seems to be no one willing to explain this to people unfamiliar with analog circuits. I'd like any…
Keith
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13
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1 answer

The Difference Between Bilateral Filter and Gaussian Filter

I would like to know the basic differneces between Gaussian filter and Bilateral filter in digital image processing... I just know that both are used to smooth out an image but I would really appreciate if somebody let me know what is the purpose…
Aayman Khalid
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13
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4 answers

Minimum Phase - All Pass Decomposition For Large Linear Phase Filters

UPDATE: I am looking for a robust approach to decompose linear phase FIR filters with 100s of coefficients into its minimum phase and all pass components. I originally thought determining all the zeros from the coefficients would be a mathematical…
Dan Boschen
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3 answers

Mapping of Classic Filters for Digital Filter Design

Of the four classic analog filter types: Butterworth, Chebyshev, Elliptic and Bessel- are any of these relegated to obsolescence for purposes of digital filter design in comparison to optimized algorithms such as least squares (firls),…
Dan Boschen
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How does subpixel image shifting using DFT really work?

I am trying to assess the quality of several image interpolation methods for an application that involves generating subpixel-shifted images. I thought I could compare the results of a subpixel shift using all these interpolation variants with some…
neuviemeporte
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3 answers

ADC performance simulation: How to calculate SINAD from FFT?

While working on this problem, I started to have doubts that my initial definition of $$SINAD = 10 \log_{10} \left( \frac{p_f} {\sum_i{(p_i)} - p_0 - p_f} \right)dB$$ is correct. In this equation, $p_x$ is the power the FFT bin at frequency $x$,…
FriendFX
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9 answers

Estimate Sine Frequency under White Noise — simple and effective method

Given a sinusoidal signal in white noise, how can one efficiently determine its frequency?
RyanRonald
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13
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3 answers

FFT time domain average vs frequency bin average

I have multiple trials of physiological data. I am doing a frequency based analysis to analyze power (amplitude) in certain frequencies of interest. Is averaging multiple trials of equal length and then taking a single FFT of the averaged signal vs…
user1487551
13
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2 answers

What Is the Algorithm Behind Photoshop's "Black and White" Adjustment Layer?

Can someone explain the algorithm behind the "Black and White" adjustment layer in photoshop? I have to reproduce it using C++ for an application that emphasizes non-red/magenta(ish) pixels from an image (with a percent-like configurable…
Blamoo
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monochrome (1-bit black-and-white) image conversion

When converting scanned text to a 1-bit black-and-white image what are some filters that one can apply in the process to improve the result? Right now I am running into the problem where dithering errors make the image look horrible. Update: I…
m33lky
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