# Tag Info

Accepted

### Convolution with the Inverse FFT of a Box Filter

It's just a scaling factor that you have been inconsistent with, as you suspect. To make the two approaches match, either get rid of the following line or multiply your fft approach by ...
• 666

### CZT: Do Bluestein algorithm perform backward transformation?

Reversing the sign of the exponent in the CZT only results in the inverse CZT for transforms on the unit circle ($A_0 = 1$ and $W_0 = 1$).1 This is noted in the actual ICZT paper cited by the OP. For ...
• 1,906
1 vote

### Phase shift between X and Y components of the same wave

From the OP's plot we can clearly see the quadrature relationship between the signals: I don't recommend using the FFT to extract phase vs time, as we can get that more directly from the scaled ...
• 52.3k
1 vote

### Phase shift between X and Y components of the same wave

These are narrow band signals. The phase at most frequencies that are outside of the band are undefined or dominated by noise. You need to evaluate the phase difference at the exact center frequency ...
• 45.6k
1 vote
Accepted

### Is the analytical fourier transform of an exponential decay the same as the FFT of a time series of the same signal?

The main problem here is that you want to evaluate the transfer functions over a complex plane. For continuous systems that's typically done using the Laplace Transform and for discrete systems you ...
• 45.6k
1 vote

### Finding a certain animal from wildlife audio

Template matching is deemed a classical approach to attack this problem. An alternative state-of-the-art method is to use deep learning (CNN) classifier given your data is labeled. However, if you ...
• 459
1 vote
Accepted

### How to do spectral averaging to get satisfactory results?

The following line in your code is incorrect for setting the phase: ...
• 666

• 459
1 vote

### Baseband downconversion without imaging

Keep in mind that multiplying an input time-domain signal by a cosine wave (or a sine wave) is "modulation" and NOT "frequency translation." To implement frequency translation you ...
• 5,837

### Inverse filtering to undo a convolution blows up

A better approach would be to apply some method to solve problems on the form $$\min_v \|Mv - d\|$$ or possibly $$\min_v \|M(v+d) - d\|$$ Where $M$ is the Gaussian convolution operation, $d$ is the ...
• 453
Accepted

### ECG analysis in MATLAB

A few points to discuss IIR filter are typically minimum phase and FIR are typically linear phase. That's not always the case, but good enough for the current discussion. Linear phase filters are good ...
• 45.6k

### Is it possible to find the FFT of a 1024-point signal by taking 8-input points at a time and calculating the FFT of those 8-points until the end?

There is a divide and conquer approach to computing the FFT detailed in this PDF. Here is an implementation as in section 8.1 ...
• 121
1 vote

### Linear convolution of a 100 sample time series and a 20 tap filter in the frequency domain

So the linear convolution correct length is as you say: $$N_t + N_h - 1$$ where $N_t$ is the length of $t$ (e.g. 100) and $N_h$ is the length of $h$ (e.g. 20). This equation:  {\tt FFT}^{-1} \left ...
• 25.9k
1 vote

### Linear convolution of a 100 sample time series and a 20 tap filter in the frequency domain

I have never heard of "20 tap filter". Is that just a FIR filter with 20 coefficients? yes. (some functions for filtering make it a bit confusing what is the number of coefficients and what ...
• 31.2k

Top 50 recent answers are included