Linked Questions
13 questions linked to/from FFT of any sinusoidal signal -- how many point fft to take?
117
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4
answers
52k
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Why is it a bad idea to filter by zeroing out FFT bins?
It's very easy to filter a signal by performing an FFT on it, zeroing out some of the bins, and then performing an IFFT. For instance:
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- 15.7k
26
votes
4
answers
9k
views
FIR Filter Design: Window vs Parks McClellan and Least Squares
Are there any advantages to use a window approach over Parks-McClellan (further abbreviated here as PMcC) or Least Squares algorithms for FIR filter design of a low pass filter? Assume with today's ...
- 48.8k
29
votes
3
answers
21k
views
What should be considered when selecting a windowing function when smoothing a time series?
If one wants to smooth a time series using a window function such as Hanning, Hamming, Blackman etc., what are the considerations for favouring any one window over another?
- 487
10
votes
4
answers
7k
views
Intuition for sidelobes in FFT
I was wondering if there's a intuitive way to understand why sidelobes appear when performing an FFT on a signal of fixed length?
- 374
9
votes
3
answers
31k
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Number of DFT (FFT) Points Required for a Specific Frequency Resolution for an Oversampled Signal
I have a bandpass signal centered at 2 MHz and bandwidth of 50 kHz (the signal frequency varies from 2 MHz - 25 kHz to 2 MHz + 25 kHz). This signal is being sampled at 10 MHz.
I want a frequency ...
- 634
13
votes
2
answers
7k
views
Why would one use a Hann or Bartlett window?
Suppose we're designing a low-pass FIR filter, and I want to use one of these three windows: Bartlett, Hann or Hamming. From Oppenheim & Schafer's Discrete-Time Signal Processing, 2nd Ed, p. 471:}
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- 4,980
13
votes
2
answers
29k
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FFT frequency resolution
I'm having some problems understanding the FFT. Is the frequency resolution in the spectrum calculated as
$\frac{\textrm{sampling rate}}{\textrm{number of FFT points}}$ or $\frac{\textrm{sampling ...
- 163
9
votes
1
answer
10k
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What happens when N increases in N-point DFT [duplicate]
I am curious about DFT, and I wrote a simple MATLAB code to test what happens when $N$ increases. I took a rectangular signal with length $L=15$, an then found th DFT of 16, 32 and 64 points. I looked ...
- 151
3
votes
2
answers
15k
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Magic of twiddle factor in DFT
In DFT calculation following formula is used
$$X[k] = \sum_{n=0}^{N-1} x[n] e^{-j2\pi\frac{kn}{N}}$$
where the Twiddle factor is known as complex root of unity, that is a complex number $W_N$ such ...
- 333
-1
votes
1
answer
4k
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Aliasing after downsampling [duplicate]
Let me start with time domain representation of the original signal
\begin{equation}
x_n=\sum_{k=0}^{2N-1}X_ke^{j\frac{2\pi nk}{2N}}
\end{equation}
where $2N$ is number of time/frequency samples ...
- 181
0
votes
1
answer
2k
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Specific Frequency Resolution
I have an audio signal
SampleRate Fs: 44100 Hz
TotalSamples: 94144 samples
Duration t: 2.1348 s
The frequency resolution is given by ...
- 132
1
vote
2
answers
2k
views
Different way to separate a particular frequency from a signal
Let's say I have a signal which is composed of 2Hz,10Hz,17Hz,19Hz and 25Hz discrete time sinusoidal waves and I need to allow only 17Hz component to pass.
As far as I know, the standard way to ...
- 29
0
votes
1
answer
1k
views
FFT and number of samples relations
I am new in signal processing. I generated a signal with $f_{in}=10 \mathrm{kHz}$ and also take 64 sample from this signal after doing some process in an ADC block. I want to convert the result to the ...
- 1