The fourier-series tag has no usage guidance.
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12 views
Find Fourier series $f(t) = e^{jx t}$ , $−\pi < t < \pi$
I need to find the Fourier series of the $f(t) = e^{jxt}$ , $− \pi < t < \pi$
What will be the first step to solve it?
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2answers
66 views
Why do frequencies of analog signals range from $-\infty$ to $\infty$ while frequencies of digital signals are restricted to $[0,2\pi]$?
In Fourier analysis while dealing with discrete-time signals, frequencies range from $0$ to $2\pi$ why? Intuitively how can i understand it?
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2answers
136 views
Scaling property of Fourier Transform
Problem 4.6(b) from Oppenheim, Wilsky & Nawab (2nd ed) reads:
Given that $x(t)$ has the Fourier transform $X(j\omega)$, express the Fourier transform of $x(3t - 6)$ in terms of $X(j\omega)$.
The ...
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2answers
47 views
Fourier series of $cos(\omega_0 t)$ in continuous time
Can any one please help me with understanding how we can calculate the Fourier series of Cos(w0t) using the formula:
I saw that they did the following calculus, but I Don't really understand how we ...
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0answers
21 views
From Fourier (k space) to wavelet domain in MRI sensing
In compressed sensing MRI (cSENSE MRI) technology the idea seems to entail sampling from the Fourier domain (k space) in a way that, when transformed to the wavelet domain ("sparsification"), the ...
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0answers
48 views
Cosine Fourier Transform and Phase
If we do FT of cosine wave, then sine wave will be orthogonal. So, the imag parts of FT will be 0. This is my think. But, the result isn't show that. Like this.
Figure 1. Real and Imag parts (Y label ...
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0answers
36 views
calculation of derivative using FFT
Here is my issue:
I am trying an algorithm using FFT to fit and get a function's approximative in order and calculate it's derivative in an more easy way ( for any data), but I get some discontinuity....
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1answer
64 views
Fourier coefficients of sum of two functions with different fundamental periods?
If we assume $\quad x(t)\leftrightarrow a_k\:$ and it is periodic with fundamental period T.
How can we determine the fourier coefficients of the sum
$x(t-7)+x(-2t+3)$
I know that $x(t-7)\...
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1answer
45 views
Is there any special when all Fourier components have the same angle?
When a square wave doesn't jump, its oscillators aren't aligned:
But if they are in sync, the wave will jump to its extrema:
However this is just an example of square waves. The tool Understanding ...
2
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4answers
77 views
What is the moment when all oscillators aligned to make a jump called?
Say we have a square wave and its Fourier series. When the wave doesn't jump, its oscillators aren't aligned:
But if they are aligned, the wave will jump:
What is this moment called? They might not ...
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1answer
52 views
How to determine which Fouriers Series terms to use to approximate a signal?
I have a signal (a time-series of air temperature values) that I can approximate quite well with a Fourier series. However, the number of terms in the series grows rapidly, to the point that 30 - 40 ...
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1answer
69 views
characterization of DC component
Consider the following two statements:
In time axis:
A signal without a DC component is a signal which doesn't have the zero frequency (the DC frequency)
A signal without a DC component is averaged ...
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1answer
297 views
Proof of the convolution property of Fourier Series in continuous time
I am facing problem in understanding the proof of Convolution property of Fourier Series (FS) in continuous time CT;
that is: $$\mathrm{FS} \big\{x_1(t)\star x_2(t)\big\}=T\sum_{n=-\infty}^{\infty}...
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0answers
27 views
Applying a filter described by differential equations to a signal with autoregressive noise
I have been trying to resovle a problem for quite some time now without success. It is a signal processing issure, so I hope here I can find the help I need. I use Scilab for my computations, but I am ...
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1answer
54 views
Uniqueness of Fourier Series Representation and the Fourier Transform of Periodic Signals
If we are given a signal of the form $$x(t) = \sum_{k = -\infty}^{+\infty} a_k e^{j k \omega_0 t},$$ can we call it a Fourier Series representation of $x(t)$ right away?
Suppose we are given the ...
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0answers
14 views
Fourier series coefficients if time period changes [duplicate]
We have to find the Fourier series coefficient of x(t) = cos(2πt) if we were to regard it as a signal with period=3 when it's fundamental period is 1.
Now I have a doubt.
Since it's fundamental ...
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1answer
45 views
Fourier Coefficients
Consider the signal
$$x(t)=\cos(2\pi t)$$
Since $x(t)$ is periodic with a fundamental period of $1$, it is also periodic with a period of $N$, where $N$ is any positive integer.
What are the ...
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1answer
46 views
What is the exact meaning of the output of the Discrete Fourier Transform
I'm fairly new to the subject, but so far my understanding that this would be a transform you could use to go from a discrete set of data, say [1, 0, 1, 2] to a continuous sinusoidal function in the ...
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1answer
40 views
Inverse Discrete-Time Fourier Transform of $X(Ω)=jΩ$
I am trying to solve it by using the properties but I can’t seem to find the same solution as on my book.
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1answer
52 views
Fourier components of $\cos(2\pi f_1t)$
I have the signal $s(t) = \cos(2\pi f_1t)$ and I am looking for its components vs the Fourier basis, over the interval $[0, T]$. The formula for computing the coefficients is
$$
s_n = \int_{t_0}^{t_1} ...
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1answer
64 views
Fourier coefficients of product of two periodic signals
question:
If $x(t)$ and $y(t)$ are two periodic signals(both with period T) with Fourier coefficients $c_{n}$ and $d_{n}$ respectively then, Fourier coefficient of $z(t)=x(t)\cdot y(t)$ is:
(a) $\...
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2answers
352 views
Finding the fundamental frequency of a periodic signal
Suppose we have the signal $$x(t) = e^{j\omega_1 t} + e^{j\omega_2 t} + e^{j\omega_3 t},$$ where all the frequencies are rationally related (that is, the ratio of any pair of frequencies is a rational ...
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1answer
40 views
Rationally related frequencies and the Fourier Series representation
Suppose that we have the signal $$x(t) = e^{j\omega t} + e^{j\frac{3}{2} \omega t},$$ and we want to find a Fourier Series representation for that signal. Is this possible? According to my ...
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1answer
40 views
Pulse wave question
Wikipedia, fount of all knowledge (Ha! LOL), gives a formula for a pulse wave here:
The formula is:
$$f(t)=\frac{\tau}{T}+\sum_{n=1}^{\infty}\frac{2}{n\pi}\sin\left(\frac{\pi n \tau}{T}\right)\cos\...
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2answers
59 views
Fourier Series of Aperiodic convolution of periodic functions
we were given the following classic exercise:
Given two periodic signals $x(t), y(t)$ with fundamental period $T$
with Fourier series coefficients $c_m^x, c_m^y$ respectively, find the
Fourier ...
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0answers
53 views
Sampling and filtering of a signal
I have following question and I did the first part.When I came to part b and c I didn't understand how we define b(t) or z(t).Can you give me idea?
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1answer
125 views
Consider an ideal low pass filter $H(\omega)$, and the input to this filter is the periodic square wave $x(t)$. Find the output $y(t)$
The solution to the problem is $$y(t) = 5 + \frac{20}{\pi} \sin(\pi t) + \frac{20}{3\pi} \sin(3 \pi t) $$ and to get that the solution says to find the Fourier series expansion of $x(t)$ and I am ...
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0answers
42 views
Plotting frequency spectrum
How do I plot frequency domain of
$$y(t)= 3\sin (2\pi3000 t) + 2\sin (2\pi16000 t)$$ at a sampling frequency of $20\,\text{kHz}$? I know that I should use FT, but still I'm not sure how to plot it. I ...
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2answers
127 views
Fourier series coefficient of signal when Time period is twice the fundamental period
My try:
First of all I tried observing the symmetry but I did'nt find any.So I tried to calculate the fourier series coefficient of the signal like this
First I differentiated the signal $x(t)$ so ...
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1answer
621 views
How to do simple extrapolation with Fourier transformation?
I have 1024 sample points, and I would like to do really simple extrapolation using Fourier transformation. First I apply Fast fourier transformation on the data. My first intuition was that I just ...
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0answers
29 views
Efficient format for 2D signal?
I'm trying to solve the following problem. I got a "low frequency" input 2D signal over a square region. I'll collect a few samples, somewhere around 10-30 maybe, the exact sample count will be ...
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2answers
116 views
Explanation of fundamental filtering's consequences on signal
Can anyone explain why exactly an "Overshooting" phenomena is observed when the fundamental harmonic is removed as seen on the figures? Is it technically right to call this "overshooting" at all ? If ...
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2answers
96 views
Fourier transform
Fourier transform of a DC signal is an impulse at the origin.
Now if the spectrum of a signal is the plot of the amplitudes of the respective frequencies of each harmonic, then the Fourier transform ...
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1answer
189 views
Fourier series coefficients
Question:
The fourier series coefficients is given as:
$$c_k= \begin{cases}
1 \qquad & k \ \text{ even} \\
2 \qquad & k \ \text{ odd} \\
\end{cases}$$
the period of the signal is $T=4$, ...
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1answer
1k views
Fourier series - time shift and scaling
What will be the new Fourier series coefficients when we shift and scale a periodic signal?
Scaling alone will only affect fundamental frequency. But how to calculate new coefficients of shifted and ...
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1answer
80 views
Dirichlet Conditions
What is meaning of a signal having a "finite number of maxima and minima during any single period of time"?
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1answer
240 views
Difference between frequency components and harmonic components - Fourier
What is the difference between frequency components and harmonic components? The first concern the continuous domain of frequency, while the second concern the discrete domain of frequency ($f_{k}=kf_{...
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2answers
94 views
Can I compute Fourier series without looping through all frequencies?
I need to compute Fourier series of an audio stream.
But DFT/FFT is slow.
Are there any ways to compute Fourier series of a signal without using the Fourier transform to check if whether a frequency ...
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3answers
2k views
How to get the Fourier series using Python's $\tt fft$
I Would like to be able to reconstruct every individual sinusoid that makes up a Discrete signal. I Have the following signal: (I am working in Python)
The signal is essentially an array with about ...
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1answer
59 views
Why doesn't a sudden loud noise sound high pitched?
The jumpiness or high change of a signal is due to the higher frequency components in the signal. So if I have a sound signal that increases suddenly in amplitude, why doesn't the signal sound very ...
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0answers
96 views
Problem on Complex Fourier Series
I am trying to solve this problem but I am stuck. Please I would appreciate if some one guide me on how to proceed
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1answer
270 views
Fourier series approximation: DC component and fundamental frequency
In the linked image below, what is meant by plotting the DC component and fundamental frequency for a Fourier series approximation?
For dot point 1 does it want me to graph just the DC component ...
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1answer
35 views
How can $a_n$ for the trigonometric Fourier series be $0$ for a non-odd square signal?
Can $a_n$ for the trigonometric Fourier series be $0$ for a non-odd wave? Since at the moment the square wave is not even nor odd. Square wave is given by:
$$
s_2(t)=\begin{cases}
-4, & 0\leq t\...
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1answer
79 views
Why can Fourier series be used on a non-repetitive function?
I was just wondering why Fourier series can be used on the function in the linked image. This is since I thought the function had to repeat itself to use Fourier series on it. Or is it saying a period ...
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2answers
82 views
Basic Fourier Series Not Understanding how to interpret n values [closed]
I have a question regarding $n$ in the Fourier series. If a question states "find the Fourier series for (any function) and find the values of an $b_n$ etc", say I'm finding it from the trig way when $...
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2answers
474 views
How can understand periodicity of a Signal from frequency domain representation?
Is it possible to say a signal is periodic from its frequency domain representation? A periodic signal is sum of its sinus and cosinus. Frequency translation of sinus and cosinus functions are ...
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4answers
333 views
Why are wavelet transforms (Multi Resolution Analysis) used more in practice for compression rather than Fourier series?
I know that both Fourier and wavelet can be used for compression of signals.
The Fourier series guarantees that it gets the closest approximation of the original signal in the least squared sense. ...
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1answer
133 views
Unipolar Transmission Spectrum
I am currently trying to understand mathematically the amplitude shift keying modulation technique. My question is, say I wanted to compute the Fourier series of a basic pulse train, it is quite ...
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0answers
92 views
Range of function $ \frac{1}{n\pi}(1-\cos(n\pi))\sin(\frac{n\pi}{2})$ and determination of Fourier coefficients
I am computing the Fourier series expansion of the given signal $x(t)$. In that I am having difficulties in calculating range of function $ \frac{1}{n\pi}(1-\cos(n\pi))\sin(\frac{n\pi}{2})$ (or) I am ...
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1answer
327 views
fourier series fitting matlab
I am using cftool in Matlab to fit time series values to Fourier model with 8 terms:
...
