Signal Processing Stack Exchange Community Digest

Top new questions this week:

Are all LTI systems invertible? If not, what is a good counterexample?

I have been trying to figure this out for a while now. Everywhere I have looked I could easily find examples of invertible LTI systems, but I could not find any counterexamples. Can anybody shed some ...

linear-systems inverse-problem  
asked by Andrew 7 votes
answered by Matt L. 10 votes

How do impulse response guitar amp simulators work?

I am wondering how impulse response guitar amp simulators/modelers work. I thought it was a matter of convolving a signal of recorded impulse response in time-space with a guitar sample. I tried to ...

audio convolution impulse-response audio-processing  
asked by Klemen 4 votes
answered by Matt L. 10 votes

The z factor in polyphase decomposition

I'm a beginner in DSP and I'm going through the textbook of Oppenheim's Discrete Time Signal Processing. There are two figures in the text, one which I can visualize, and the other I can't. The first ...

polyphase  
asked by Lim LS 4 votes
answered by Fat32 2 votes

instantaneous frequency for a sum

In the literature, the instantaneous frequency for a signal $s(t)=e^{-j \phi(t)}$ is given by: $$f(t)=\tfrac{1}{2\pi}\frac{d\phi(t)}{dt}$$ This my problem: I have a signal $$u(t)=e^{-j \alpha_1 ...

frequency-spectrum digital-communications frequency  
asked by user46213 2 votes
answered by Fat32 3 votes

Amplitude estimation of sinusoid in known spiky spectral noise

What is the "best" way to estimate amplitude of a known-frequency sinusoid in the presence of known spiky spectral noise (i.e. noise comprising a few spectral peaks at known frequencies)? By ...

noise dft estimation amplitude  
asked by abc 2 votes
answered by Cedron Dawg 1 vote

I don't understand harmonics, why do they happen?

I don't understand why harmonics occur in signals. So if I receive a time domain sinusoidal signal at 10 Hz and I perform the FFT of it, I will observe peaks at 10 Hz, 20 Hz, 30 Hz, and so on... with ...

fft  
asked by digeridoo 2 votes
answered by hotpaw2 2 votes

What are the measurable factors of image sharpness?

I need a way to present data on an essay written about image sharpening algorithm. So I've thought that if I measure a factor of sharpness from image or relative sharpness (between test img and ...

image-processing image photo  
asked by Kacper 2 votes
answered by Victor Deleau 0 votes

Greatest hits from previous weeks:

Calculating values of frequency bins in Python

I have to use FFT to determine the period of waves inside a signal. After applying FFT on a window of 10000 point from a signal, I get something like this: What I don't understand is that FFT is ...

fft frequency python scipy  
asked by Hamza Tahiri 4 votes

what's the pass band ripple and stop band attenuation of a digital filter?

Hi i'm a beginner in signal processing i want to know what'sthe pass band ripple and stop band attenuation of a digital filter ? Thanks.

filters digital  
asked by afef 4 votes
answered by Dan Boschen 8 votes

What is the distinction between ergodic and stationary?

I have trouble distinguishing between these two concepts. This is my understanding so far. A stationary process is a stochastic process whose statistical properties do not change with time. For a ...

random ergodic  
asked by Matt 42 votes
answered by Dilip Sarwate 33 votes

Question About $ Q $ Matrix (Model Process Covariance) in Kalman Filter

I am implementing my own discrete Kalman filter to estimate velocity from acceleration and position measurements (using Matlab ). I think I managed to deal with the $R$ matrix (measurements noise ...

matlab kalman-filters  
asked by Rhei 4 votes
answered by Bálint Fodor 6 votes

How to analyze audio input/spectrum correctly

I am quite new to Java and Signal Processing, but I was assigned a project dealing in audio processing. My topic given to me is a game that has a component of analyzing a song (any given song) and ...

fft audio java  
asked by user3241507 8 votes
answered by bone 8 votes

How to compute magnitude and phase response from transfer function in Z-domain?

I have a transfer function $$H(z)=\frac{1+1.2z^{-1}+0.8z^{z^-2}}{1-0.9z^{-1}}$$ from which I'm supposed to sketch the magnitude and phase response. I know that you can transform $z=e^{j\omega}$ to get ...

phase infinite-impulse-response transfer-function z-transform magnitude  
asked by markus 2 votes
answered by Matt L. 1 vote

Difference between Nyquist rate and Nyquist frequency?

So I've been searched online and can't seem to find a clear cut answer to this question. From my understanding, the Nyquist rate is double of the maximum frequency of a signal which Nyquist frequency ...

sampling nyquist  
asked by QQStack 5 votes
answered by MBaz 12 votes

Can you answer these questions?

RF direct conversion down to DC and signal recovery from IQ

I've previously worked with super-heterodyne receivers where the IF spectral content has been above DC. Reading the below tutorial; direct down conversion receivers are used to mix a signal of ...

demodulation software-defined-radio  
asked by electronpygmy 1 vote

get poles and zeros of frequency response

I am working on a python based LTSPICE project. I would like to get poles and zeros of AC simulation data. Is there a way to get them under use of the magnitude and phase out of the frequency ...

python frequency-response frequency-domain poles-zeros  
asked by Andre 1 vote
answered by Hilmar 0 votes

FFT strong signal in middle frequency bin

I've developed a radar that I'm using to determine the distance to remote objects. It uses a custom PCB with an onboard FPGA that performs the DSP algorithms. The data from it is then plotted on a ...

fft fir window-functions radar  
asked by MattHusz 1 vote
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