## Top new questions this week:

### How to improve an FFT AM demodulator for NOAA APT satellite imagery?

My question involves proper FFT Technique for AM demodulation, in the special case where the modulation rate exceeds the carrier frequency. This question has a specific hobbyist application, the ...

fft image demodulation

### Realization of IIR resonator

The measure of a given frequency $\omega$ in a signal $x(t)$ is: $\frac{1}{N}\sum\limits^N_{t=0}x\left(t\right)e^{^{-i \omega t}}$ This is basically an average of the correlation between the signal ...

fourier-transform infinite-impulse-response moving-average

### How does taking the absolute value of a complex signal reflect in the frequency domain?

I have a frequency-domain representation $F[n]$ of the complex discrete one-dimensional signal $x[n]$: $F=\mathcal{F}(x)$. Is there a frequency-domain transformation of $F$ into $F'=\mathcal{F}(|x|)$? ...

fourier-transform frequency-domain

### How to extract IF (instantaneous frequency) from Discrete Hilbert Transform?

The continuous time Hilbert transform is $$\hat x(t) := x(t) + j\left( p.v. \left\{\frac{1}{t\pi} \ast x \right\} (t)\right)$$ where  \theta(t) = \tan^{-1}\left( \frac{ p.v. \left\{\frac{1}{t\pi} ...

filters discrete-signals transform hilbert

### Audio Recognition and Learning

I'm a beginner with absolutely no experience in signal processing, but it has been a long-term goal of mine to do something that mixes music (a hobby of mine) and computer science (my "expertise"). ...

audio signal-analysis machine-learning

### Construct a correlation matrix using the covariance method

I want to compute the autocorrelation matrix by using the covarience method. X(n) is the harmonic process $X(n) = \sum\limits_{i=1}^3 A_i e^{jn\omega_i} + V(n)$ $V(n)$ is unit variance noise. \$ ...

autocorrelation

### Direct Form I Filter from Direct Form II

I am looking a way to make outputs match. For len 160 wouldnt the error be significant? For 40 ? I have included some sample output showing the error. Direct Form 2 Original void highpass(const ...

filters c

## Greatest hits from previous weeks:

### What are linear and circular convolution?

I have some basic understanding of signals and convolution. As far as I know it shows the similarities of two signals. Could I get some explanation in plain English of: what are the linear and ...

convolution

### QPSK Modulation/Demodulation in C++

I'm trying to implement a QPSK Mod/DeMod system in C++. So far i have a bit generator that generates N bits and stores it into an array: srand(time(0)); for (int i = 0; i < N; i++) { ...

matlab modulation digital-communications demodulation qpsk

### Normalized cut segmentation output correct or not?

I have implemented "normalized cut" segmentation. The change here is that, instead of giving an image as input, I have given an matrix of image. As my output looks odd to me. I need to know whether my ...

image-processing matlab computer-vision image-segmentation