Bandwidth of a DC signal

Hello,

I read this statement in one of university handouts and can't figure it out...

"If the signal's frequency content goes all the way down to zero ("DC") then its bandwidth must be twice its centre frequency and its fractional bandwidth equals two. This is a strictly baseband signal"

So we know that the frequency of the DC signal is 0, this means fH(upper freq) and fL(lower freq) both equal 0, so its BW = 0 and so does its center frequency (f mid)...

So we know that the frequency of the DC signal is 0, this means fH(upper freq) and fL(lower freq) both equal 0, so its BW = 0 and so does its center frequency (f mid)...

Click to expand...

No. It says "signal frequency content" Meaning the signal's bandwidth is from DC to fH, and the center frequency is fH/2.

oh that clears things up !
thank you