Questions tagged [fourier]

Anything related to Fourier series, Fourier transform and similar mathematical tools used to analyze the frequency content of a signal.

64 questions with no upvoted or accepted answers
Filter by
Sorted by
Tagged with
4 votes
1 answer
282 views

FSK Modulation in Python

I am currently writing a script that uses I/Q data to do FSK modulation. My question is about the FFT plot. I expected to have a peak at 1Hz and 2Hz which are the frequencies that represent binary 0 ...
PrematureCorn's user avatar
3 votes
0 answers
70 views

Finite-duration signal in the time domain, means what exactly in the frequency domain?

I'm trying to understand exactly what restrictions a finite duration time domain signal has on its Fourier transform. I found a helpful table in The Fourier Transform and its Applications by Ronald ...
Robbie Rosati's user avatar
2 votes
0 answers
76 views

Why does a cosine function have a non-infinite Fourier coefficient?

I took my signals class a long time ago and have gotten used to using Fourier tables for a lot of things. I'm reading a textbook on communications and I stared at the Fourier transform equation for a ...
CEEA's user avatar
  • 41
2 votes
0 answers
381 views

Pulse Doppler radar system simulation using MATLAB

How to code this project in MATLAB I'd tried coding this project (prob. 3-2, third paragraph) in MATLAB through this tutorial : https://www.mathworks.com/help/phased/ug/doppler-shift-and-pulse-doppler-...
Ali Ent's user avatar
  • 121
2 votes
0 answers
74 views

Representation of Fourier transform

I have a problem interpreting 2 different representations of Fourier transform and proving their property. In some texts Fourier transform is represented as: $$ \begin{align*} x(t) = \frac{1}{2\pi} &...
beta_me me_beta's user avatar
2 votes
0 answers
120 views

Fourier transform of the electrical conductivity function

In this pdf https://studylib.net/doc/18704299/chapter-1 the author writes that the Fourier transform of the current density is: $$ \Delta j_{i}(\mathbf{k}, \omega) \equiv \frac{1}{(2 \pi)^{2}} \iiiint ...
Logi's user avatar
  • 121
2 votes
0 answers
536 views

Vanishing of Gibbs Phenomenon in MatLab

I was trying to represent a square wave with its Fourier series in Matlab. But as I increased the number of terms in Fourier series expression, the Gibbs phenomenon vanished and the edges of the ...
Muhammed Roshan's user avatar
1 vote
1 answer
65 views

Discrete Fourier transform for musical analysis

I am a senior in highschool and am currently trying to conduct an exploration on Fourier analysis, specifically using the discrete Fourier transform to analyze a chord played on my piano. Basically I'...
Ralph Khouri's user avatar
1 vote
1 answer
73 views

A DFT-based phasor estimation

I have the sample set of ideal and real secondary current during CT saturation, need to apply the DFT analysis to samples and estimate the fundamental phasor (magnitude and phase angle) of samples (...
sakayevas's user avatar
1 vote
0 answers
138 views

Numpy giving the wrong Fourier transform of sine functions

I'm using numpy's FFT to calculate the Fourier transform of \$\cos(\omega_0t)\$ and plot it. By using the definition we can derive its Fourier transform as below: \begin{equation} X_3(j\omega) = \pi (...
nothatcreative5's user avatar
1 vote
0 answers
106 views

Frequency domain analysis when sampling a switched (gated) integrator

I would like to use AC analysis (e.g. in spice) on a non-ideal op-amp integrator where the reset switch is open, and then apply a shaping function to the result of the AC simulation (in the frequency ...
HKOB's user avatar
  • 1,130
1 vote
1 answer
229 views

Fourier Transform Time Scaling Property using f (frequency) or w (omega - angular frequency)

The time scaling property for a fourier transform is as follows: My book shows this property in terms of \$f\$; however, my instructor likes to use \$\omega\$. I have also seen this property written ...
Jake Baker's user avatar
1 vote
0 answers
59 views

Interpreting Fourier transform of Images

I'm new to image processing and am learning about the Fourier transform. I've read that FT decomposes a function to its constituent frequencies. However, I'm not sure how to tell which is a low ...
ghostOfElysium's user avatar
1 vote
0 answers
485 views

Raspberry Pi and FFT (Fast Fourier Transform) -- Using MCP3208

EDIT: I've made adjustments based on your answers, while I couldn't get it to be evenly spaced, I managed to get a better curve with more samples per cycle. Turns out I need to remove the print ...
Hazman Hussin's user avatar
1 vote
0 answers
309 views

Total harmonic distortion and DFT

I am trying to understand a design that would enable us to measure/determine the total harmonic distortion. Key points: The system is microcontroller (TI, C2000, dual-CPU) driven electronic It has a ...
WedaPashi's user avatar
  • 1,670
1 vote
0 answers
215 views

Apparent lack of rigor in Phasor domain analysis of steady state AC circuits

so I have encountered a hitch in my understanding of analyzing steady state AC circuits. I have looked everywhere for the answer to my question and I can find nothing. Usually when we analyze ss AC ...
EECE's user avatar
  • 93
1 vote
0 answers
72 views

What exactly does the frequency spectrum represent?

The signals in the image represent a low pass signal and its Hilbert Transform. I know that a plot for a signal's magnitude with reference to frequencies can be found by applying a Fourier Transform. ...
Paddy's user avatar
  • 225
1 vote
1 answer
128 views

Spectral analysis of spectrum analyzer

Using measures from a spectral analyzer, I am a bit confused on how to properly compare the power of each spectral line with the fourier coefficients (Parseval). Take this signal: Take its spectrum: ...
Yannick's user avatar
  • 447
1 vote
0 answers
110 views

Calculating real part of a square wave

i'm trying to understand how Bruno putzey in Globally Modulated Self-Oscillating Amplifier with Improved Linearity in section 4.2 Analysis comes to the equation in presented in (2), see snapshot below....
user103776's user avatar
1 vote
0 answers
73 views

Fourier series and Fourier transform of signals which can be generated in real world

Let first remind on Dirichlet conditions: In mathematics, the Dirichlet conditions are sufficient conditions for a real-valued, periodic function f to be equal to the sum of its Fourier series at ...
etf's user avatar
  • 115
1 vote
0 answers
992 views

Application of Fourier Series in Circuit

I am trying to find \$v_o(t)\$ in the circuit below, where $$v_s(t) = 3 - \frac{6}{\pi}\sum_{n=1}^{\infty}\frac{1}{n}\sin2\pi n t$$ The correct answer is $$v_o(t) = \frac{3}{2} - \frac{3}{\pi}\sum_{n=...
eLg's user avatar
  • 179
1 vote
0 answers
930 views

How to get fourier series of 8-bit character to be transmitted?

I have been reading this in a book, but can't understand how he used the 8-bit in fourier series equation to get the result below. The transmission of the ASCII character ‘‘b’’ encoded in an 8-bit ...
Ali Zahr's user avatar
0 votes
0 answers
32 views

Z transform and the magnitude of Fourier transform

Would like to know if the graph of the magnitude in the picture I added is correct. Should I address the other pole?
Adi Goyte's user avatar
0 votes
1 answer
85 views

Sketching fourier transform after sampling

I'm having trouble understanding how this system is supposed to work. My sketch (all my sketches are for fourier transforms) for \$X_b(jw)\$ are two pyramids centered at 7pi and -7pi with height 1/2. ...
Ray's user avatar
  • 159
0 votes
0 answers
89 views

How to properly take the discrete Fourier transform of a signal as well as calculate the power spectral density of the DFT?

I'm getting conflicting answers on how to properly represent a DFT and normalize the results as well as calculate the normalized PSD of the time series. For background, I typically work with voltage ...
Simeon K's user avatar
0 votes
1 answer
60 views

Need help on signals and systems, Fourier representation of a signal

I've got a homework question for my signals and systems class. In the question, we're given the graph of the magnitude and the phase of a continuous signal. Here are the graphs: I have to find the ...
the big's user avatar
0 votes
0 answers
90 views

FFT analysis in LTSpice is giving wrong results during partial execution of time domain simulation (Details in body)

In LTspice, while computing FFT using waveform window (View-> FFT), the results seems to be wrong if FFT is computed after partial execution of simulation ( eg: if simulation is paused in between)...
Divya K.S's user avatar
  • 2,908
0 votes
0 answers
27 views

Converting Laplace to CTFT to find solution

Let us take a system where the input is \$V_{i}(t)\$ and output is \$V_{o}(t)\$ and the impulse response of the system be \$I(t)\$ where \$t\$ represents time domain and \$w\$ be frequency. we get \$\...
Moulee's user avatar
  • 7
0 votes
2 answers
64 views

Fourier transform plot

A continuous-time signal x with bandwidth \$\frac{20π}{3}\$ rad/sec is sampled with sampling period \$T_s = 0.1\$ seconds to obtain a discrete-time signal \$x_s[n] = x(nT_s)\$ for all n. The discrete-...
kene02's user avatar
  • 538
0 votes
1 answer
119 views

Transfer function of two frequency spectra

When you have two amplitude frequency spectra (fourier spectrum), in this case of a torque ripple, how do you define the transfer function (or the ratio) between both? How do you "divide" ...
Livio Luyten's user avatar
0 votes
0 answers
161 views

A half-wave rectified sinusoidal waveform has a peak voltage of 10V. What are its average value and the peak value of the fundamental component?

I know to to find average value: 10/pi What does "peak value of fundamental component" mean?
Vedhant Abrol's user avatar
0 votes
1 answer
126 views

Why am I getting linear phase?

I'm trying to plot the phase of Fourier transform of the function below: \begin{gather*} x[n] = 2e^{-0.9|n|} \: \: n \in [-5,5]\\ x[n] = 0 \:\: n \notin [-5,5] \end{gather*} which is equal to the ...
AmirHossein Bagheri's user avatar
0 votes
0 answers
64 views

How to use DFT to find harmonic content of an AC waveform?

I am kind of new to this coding and simulation environment. For my first project I need to take samples of current signals from power line and find out the harmonic contents using DFT. I haven't done ...
Vineeth's user avatar
0 votes
0 answers
94 views

Circuit analysis problem involving Fourier series

Please help me with this problem I can not solve this. It is about Fourier series. It is so hard.
Pham Duc Thuan's user avatar
0 votes
0 answers
44 views

how to define a relative bandwidth for the signal with the equation K/w^2

I have a straight line with a slope. Thus its fourier transform is K/w^2. I wanted to estimate its relative bandwidth(Wont it be dependent on the slope?[1st question]). If the answer for 1st question ...
Hari Krishna's user avatar
0 votes
0 answers
38 views

Relationship between two differently sampled Fourier coefficients

Assume a periodic signal \$s(t)\$ with fundamental period \$T_0\$. If one were to use the period \$kT_0\$ to find the Fourier series coefficients, how would they be related to the standard Fourier ...
SacredMechanic's user avatar
0 votes
0 answers
40 views

partially periodic function and fourier series representation

I am thinking about this for a while but I could not reach a conclusion. If I have a periodic signal let's say a square wave but it is only non-zero for t<100 and t>-100. the function is ...
EEguy's user avatar
  • 177
0 votes
0 answers
114 views

can fourier transform be used in circuit design?

If I formulize the input voltage that I am planning to give to a circuit and if I formulize relative output voltage that I expect to see with respect to input voltage, I can take their fourier ...
EEguy's user avatar
  • 177
0 votes
1 answer
299 views

find current, voltage and power at each branch using fourier series analysis

Question: find current, voltage and power at each branch using fourier series analysis Update - here is my solution attempt:
Nazihah Binti Zainuddin's user avatar
0 votes
2 answers
178 views

What is the physical meaning of reactive power in non-sinusoidal steady-state (with harmonics)?

In sinusoidal steady-state (linear loads, no harmonics), I understand what is reactive power \$Q = V_{\text{rms}} I_{\text{rms}} \sin{(\theta)}\$ where \$\theta = \theta_v - \theta_i\$: its absolute ...
alejnavab's user avatar
  • 989
0 votes
0 answers
82 views

Absolute values of fourier transform of noise-charged RLC circuit

I am doing time-domain simulations of currents in a parallel RLC circuit charged by thermal noise. In detail in pseudo-code: ...
Christian's user avatar
  • 219
0 votes
1 answer
58 views

I need help with Fourier Series

I am having problems analyzing this sketch of a continuous Fourier series as it can't find a single known function
Allaaaa's user avatar
0 votes
0 answers
406 views

How to find the Fourier series of an output given input and transfer function

I have an input rectangle pulse, \$f(t) = rect(t/\tau) \$ and a transmission line whose transfer function depends on frequency. The transfer function of the t.l. is the transmitted wave divided by the ...
Hector's user avatar
  • 353
0 votes
3 answers
124 views

Fourier Series Concept

Hello, I am learning about the Fourier Transform, and I can do the math, but I'm having trouble with the fundamental concepts. From my understanding, the Fourier transform allows us to see the ...
ClockwerkSC's user avatar
0 votes
0 answers
828 views

Voltage Measurement through Spectrum Analyzer

I have done some measurements with a Spectrum Analyzer of a square wave of 100kHz and amplitude equal to 1V. The resulting power spectral density is here shown: The highest peaks represent the odd ...
Kinka-Byo's user avatar
  • 3,438
0 votes
1 answer
140 views

If I look at a signal in its frequency domain, are there some guidelines by which I can tell how that signal looks in the time domain?

I was studying the Laplace transform and the Fourier transform, and I can't figure out if there is some intuitive way of finding out how a signal looks in the time domain if we know its frequency ...
user1477107's user avatar
0 votes
0 answers
177 views

Phase, Frequency and Laplace transform

I have a doubt on the relationship between phase and frequency. We know that the definition of angular frequency is: ω(t) = d(\$phi\$(t) / dt, where \$phi\$(t) is the istantaneous phase of our ...
Kinka-Byo's user avatar
  • 3,438
0 votes
1 answer
47 views

AC signal analysis: Voltage dip (amplitude dip) at time = 0

I'm working on a series RLC problem where the input voltage is a sinusoidal function for all time. The catch is, for t < 0, the sinusoidal function is of greater magnitude than t >= 0. There is no ...
MBJ's user avatar
  • 1
0 votes
0 answers
84 views

Confused on Fourier Transform. What is amplitude spectrum and phase?

I am learning fourier transform by myself and I am confused on the description below. I can't understand how can I get the second formula by using the Euler formula on the first equation. Why is ...
TIANLUN ZHU's user avatar
0 votes
0 answers
149 views

Power of random signal in AM

I'm trying to wrap my head around this problem : I must admit I'm pretty much blocked from the start, at a). I don't understand how I could derive the power of \$s_{AM}\$ given the frequency of the ...
Yannick's user avatar
  • 447