Why does Raised Cosine Transmit Filter makes the Channel Power Smaller?

Hi,

I meet a problem while running the simulink of an OFDM communication system, that the Channel Power after a Raised Cosine Transmit Filter becomes smaller than before while the power doesn't change.

But when I change the type of Spectrum Analyzer from power to power density, we can notice that the power density also become smaller.

So, why and how does Raised Cosine Transmit Filter influence the Channel Power and power density shown in Spectrum Analyzer? How does Spectrum Analyzer measure the Channel Power and power density?

power(see below):

power density(see below):

block(see below):

parameters of Raised Cosine Transmit Filter(see below):

Thank you!

Best, Ruozhu