Simulink minimum maxium time step setting for VCO simulations.

[newmedia]

Hello all,

I received a source file of a pll simulation from my colleague.
However, I'm not in the situation to ask him about the source codes and bug him.

I understand this is tmin, tmax related setting for a VCO and PLL simulations.

Please take a look.

FFTpoints = 32*1024
Prime_Bin = 2621 %17011%
Fs = vco_freq*FFTpoints/Prime_Bin
L = FFTpoints/Fs ;
Freq_resolution = Fs/FFTpoints
%t = 0:1/Fs:L-(1/Fs);
%T0=1/f0;  W0=2*pi*f0;
%tmin=T0/1e6; tmax=T0/100; tend=500*T0; tnew=51*T0; tnewend=1200*T0;
%Fs = 100*vco_freq
T0=1/Fs; tmin=T0/1e6; tmax=T0/100; tend=1*L; tnew=51*T0; tnewend=1200*T0;

Anybody can tell me what's exactly going on? I think the codes are trying to figure out the number of samples which will faithfully reconstruct the actual waveform. Should i look at anti-aliasing tutorial?

Thank you,
Newmedia

 

[newmedia]

I think this is realted to the sampling theory. I think the orginal source code was written with consideration of FFT.

 

[AdvaRes]

I think this is realted to the sampling theory. I think the orginal source code was written with consideration of FFT.

Yeah you're right. Try a sampling rate superior than 10 time the VCO frequency and you'll get clear results.