# Frequency modulation with a certain bandwidth

I came across this sentence in this paper.

Alternatively, we modulate the frequency of the microwave excitation voltage at 971 Hz with a square wave and a bandwidth of 32MHz.

In my limited FM knowledge, this sounds like the carrier frequency is 971Hz, meaning the signal is modulated at 971 Hz. The bandwidth is the width of the signal in the frequency space. So the signal within the frequency range 16 MHz below and above the carrier frequency would be transmitted.

Given that the modulation frequency is 971 Hz, the picture I had makes little sense to me.

• 971Hz is the modulation rate, it is the rate of a square wave modulating the oscillator's frequency. If the square is between 0 and say $V_{peak}$ then the at its maximum deviation the carrier is moved by ~32MHz. For this to make sense the oscillator's frequency has to be much larger than 32MHz. Commented Oct 27, 2020 at 23:07
• Not to mention 971 Hz is way below microwave frequencies.
– Puk
Commented Oct 28, 2020 at 18:49