 ## 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

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 ... 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 ... asked by MattHusz 1 vote 