As I know, high speed transceivers always use a 0.1uF or 0.01uF capacitor for ACcoupling.
Tx>capacity>Rx

end resistor
Capacitor and end resistor are a highpass filter.
If end resistor is 50 ohm.
I calculate bandwidth with
$$
f = \frac{1}{2 \pi R C}
$$
if \$C = 0.1\mathrm{\mu F}\$, then \$f = 31.847\mathrm{k Hz}\$
if \$C = 0.01\mathrm{\mu F}\$, then \$f = 318.47\mathrm{k Hz}\$
But I always see 0.1uF and 0.01uF both used in the 1GHz, even 10GHz circuit.
As I calculated above, bandwidth should not enough.
I'm confused.
Best Answer
It's a HIGHpass filter, not a lowpass filter. That cutoff frequency you calculated is the LOWEST that can get through, not the highest. Frequencies lower than that are blocked, and frequencies higher than that are passed.