Struggling to decide the sampling frequency for this fft plot
1 Ansicht (letzte 30 Tage)
Ältere Kommentare anzeigen
Yogesh
am 24 Apr. 2024
Kommentiert: Yogesh
am 24 Apr. 2024
clear all
close all
clc
L=10;
n=1.45;
Can you guys help me with assigning the frequency values along the x axis , I am bit confused on how to determine the sampling frequency for a fft
c=2.9979e8;
dt = 6e-12;
T=10*2*L*n/c;
t = (-T/2/dt:1:T/2/dt)*dt;
Nt=round(T/dt);
fsine = 1e9;
vsine = 1;
phi = vsine*sin(2*pi*fsine*t);
EL1t=1.274e7*exp(1i*phi);
FP=fft(phi);
fs=(-Nt/2:1:Nt/2-1);
Z=plot(fs,fftshift(abs(fft(EL1t))));
0 Kommentare
Akzeptierte Antwort
David Goodmanson
am 24 Apr. 2024
Bearbeitet: David Goodmanson
am 24 Apr. 2024
Hi Yogesh,
If the time array has spacing delt (which you denote by dt) and the frequency array has spacing delf, then for an N-point fft the relationship between the two quantities is always
delt*delf = 1/N (1)
.That's because the total length of the time record is T = N*delt, and (not counting DC) the periodic function with the smallest possible frequency delf has one oscillation in that time, so delf = 1/T. The higher frequencies have n oscillations in time T and are integer multplies of delf, f = delf*n which produces the frequency grid and justifies identifying 1/T as delf. Then (1) follows.
Weitere Antworten (0)
Siehe auch
Kategorien
Mehr zu Numerical Integration and Differential Equations finden Sie in Help Center und File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!