Say I want to transmit messages using PSK:
I send the message
$$s_m(t) = \text{Re} \left [g(t) e^{\frac{j 2 \pi (m-1)}{M}}e^{j 2 \pi f_c t} \right]$$
where $f_c$ is the carrier frequency. Now my question is,
- is this a baseband representation or a passband?
- So is $f_c$ the center frequency of a certain channel? Or would we need to modulate $s_m(t)$ to the channel frequency?
- So then if we sent $s_m(t) \text{cos}(2 \pi f_b)$ where $f_b$ is the center frequency of the channel we are communicating on, at the receiver we would need to convert the modulated signal back to its low pass equivalent $s_m(t)$ so that we can apply a detection algorithm to demodulate the signal?