@David Harra, Please share th Matlab code you used to generate the simulated signal, and share the formulas you have seen.
You can estimate the frequency of the signal in the plot as shown in the enlarged screenshot below.
Two cycles = 93 pixels = 93/486 us = 0.191, therefore 1 cycle=0.96 us, which corresponds to a frequency of 10.5 MHz. When you consider the possible inaccuracy of the "2 cycle" duration measurement, this 10.5 MHz estimate is consistent with the 10 MHz value expcted fro the figure label.
The 10 Mhz frequency is often called the carrier frquency. It is amplitude-modulated to produce a pulse. Perhaps you are seeking the "frequency" of the pulse used to modulate the signal. A short pulse may be described better by its duration that by some equivalent frequency. SInce you simulated it, you can share how you did it. Please also share exactly you mean by "center frequency".
