Define the frequency axis for spectrum analyzer - Simulink

Hello, I am a student and I got this spectrum in the spectrum analyzer using Simulink:

I would like to know how to change the axis for the frequency, since it is limited from 0MHz to 250MHz. I would like to see the spectrum until 1GHz.

Answer 1

[William Rose]

@Vinícius Corrêa,

The signal used to create the spectrum you showed was probably sampled at 500 MHz. The spectrum of a signal sampled a frequency fs will go from -fs/2 to +fs/2, by default. (The spectrum can also be plotted from 0 to fs, but the spectrum from frequency fs/2 to fs will just be a folded-over copy of the spectrum from 0 to fs.) If you you want a spectrum out to 1 GHz, you must sample the signal at 2 GHz.