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# Tag Info

## Hot answers tagged frequency-domain

Accepted

### Why is the convolution of two sine waves a sinc function?

You are not convolving two sine waves, you are convolving two short snippets of sine waves. A snippet of a sine wave is the same as a real (infinite) sine wave multiplied with a rectangular window. ...
• 45.3k
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### FMCW Radar - What's wrong with the transmitted signal model?

There are two things you want to change: The frequency sweep you expect is at baseband so do not include the carrier as part of your signal. The sample rate needs to be at least $2B$ of the chirp's ...
• 2,546
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### IFFT caused inverted phase

TL;DR You should remove the conjugation of $W$ on the left half of your frequency vector and add it to your right half. For more insight as to why this has to be done read the rest of the answer. ...
• 1,314
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### Mixer and control systems

If we define "frequency domain" as the Fourier Transform: multiplication in one domain is equivalent to convolution in the other domain. So multiplication in time is the same as convolution ...
• 45.3k
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### Is a bandpass filter superfluous when the frequency band of interest after applying the FFT is below the Nyquist frequency?

There was some confusion from the OP with regards to the need to low-pass the data because of potential aliasing post sampling. These have been cleared now. For the OP’s purposes of checking if the ...
• 6,265
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 ...
• 25.8k
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 ...
• 31.1k
1 vote
Accepted

### Impulse response synthesis in the frequency domain

You can break down your transfer function into two different parts: $\frac{j \omega \rho}{4 \pi r}$ is a differentiator and $e^{-j k r}$ is a pure time delay. If we were sloppy, we could write the ...
• 45.3k
1 vote

### Freq domain filtering in a sample by sample basis

The standard way of implementing an FIR filter in the frequency domain is the overlap-add (or overlap save). See for example: https://en.wikipedia.org/wiki/Overlap%E2%80%93add_method In your case this ...
• 45.3k
1 vote
Accepted

### Frequency domain derivation of Hilbert transform of $\cos(\omega t)$

Since amplitude is not specified here, let's assume that an arrow in the figures on the right-hand side corresponds to the time-domain signal $\frac12 e^{\pm j\omega_0t}$. So the signal corresponding ...
• 90.3k
1 vote

### Calculation of frequency correlation function based on power delay profile

The PDP tells us the delay characteristics of a multipath channel, and the result in the frequency domain (as the Fourier Transform of the PDP) is telling the coherence between different frequencies ...
• 51.9k
1 vote

### Estimating acoustic sound signal energy radiated

Can i use this data to find Pressure vs time domain ? If the data is in dBSPL and properly calibrated, then yes. Otherwise no. How do i then isolate Pressure vs time domain data by subtracting ...
• 45.3k
1 vote

### Estimating acoustic sound signal energy radiated

Can i use this data to find Pressure vs time domain ? unless your "dB vs time" is already coming from a calibrated system, and dB refers to some specific physical sound pressure: no. In ...
• 31.1k
1 vote
Accepted

### What does the frequency domain of bipolar Alternate Mark Inversion (AMI) look like?

Calculating the power spectrum of the AMI code is actually a quite complicated matter, but the fact that the power spectrum has a zero at DC seems intuitively clear, as already mentioned in RBJ's ...
• 90.3k
1 vote

### What does the frequency domain of bipolar Alternate Mark Inversion (AMI) look like?

Okay, so "Google is my friend" and I found a YouTube. Bits that are zero contribute nothing to the DC component. If the number of ones in a message is even, it's as positive as often as it ...
1 vote

### Filtering in time domain vs filtering in frequency domain

QUESTION : Why is the output signal shifted in time domain? Is this because multiplication in frequency domain corresponds to convolution in time domain? A windowed sync is non-causal. In order to be ...
• 45.3k
1 vote

### How can I convert a 1/3rd octave spectrum into a linear spectrum for use as a frequency response?

This is difficult because a 3rd octave spectrum is missing a lot of information which needs to be filled in with "good" assumptions. For starters you need to determine who exactly that ...
• 45.3k
1 vote

### How can I convert a 1/3rd octave spectrum into a linear spectrum for use as a frequency response?

There aren't a lot of possibilities for this. Probably (>95%) either ISO-3 or IEC 61260 bands were used. Some googling will give you the (nominal) band centers and edge frequencies. The difference ...
• 2,368
1 vote

### Does subtracting a phase from the frequency components of a DFT output result in rotation?

After several readings and experiments, I think that the best way to rotate data exploiting the phases is to use the DFT shifting theorem. By identifying the number of shifts required to align the ...
1 vote

### Routh's stability condition

Most of your problems with this stem from confusion about terms and mixing up "criterion" and "test". Words matter! And in engineering and math, precise wording matters, so maybe ...
• 31.1k
1 vote
Accepted

### Can we do down sampling by taking fft, omitting samples on the ends of the spectrum, and then taking inverse fft?

Suppose that the the maximum frequency content of the signal is low enough that we do not have any concern about aliasing. ... Can we take the FFT of signal, then omit samples from 1023-th index up to ...
• 8,954
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### Frequency domain equivalent to center oriented rotated convolution?

The Polar FFT is about data in polar coordinate system. The operation you describe is not shift invariant, hence it can not be represented as convolution. If the number of rotations is small (Let's ...
• 19.7k
1 vote

### Generate an Ideal 2D Low Pass Filter in MATLAB

First, I will replace some of the coefficients with 0.5 and 0.25. In order to understand this, please have a look at: The ...
• 19.7k

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