Baseband vs. Passband I am a bit confused if the following signal is baseband or passband:

$f(t) = x(t) \cos(2 \pi f_c t) - j \: y(t) \sin(2 \pi f_c t),$
where $j = \sqrt{-1}$.

Since it is clearly not real, I cannot say it is passband. On the other hand, since it contains the frequency $f_c$, it should not be a baseband. Am I missing something?

Thanks,
Both real and complex signals can be passband.

Assuming $x(t)$ and $y(t)$ are baseband signals with bandwidth much less than $f_c$, then $f(t)$ is a passband signal, even if it is complex.