I was curious on why the bandwidth of the second harmonic of a PA or switch or any non linear device is twice that of the fundamental and the 3rd harmonic three times that of the fundamental tone.
Say the fundamental is modulated waveform with a lower frequency of f.1 and higher frequency of f.2, so the bandwidth is:
BW = f.2-f.1.
All the frequencies are doubled for the second harmonic, so the lower frequency of the 2nd harmonic is 2*f.1, and the upper frequency is 2*f.2, so the bandwidth of the 2nd harmonic is:
2*f.2-2*f.1 = 2*(f.2-f.1) = 2*BW of fundamental.