How to plot frequency spectrum of QPSK signal?

I'm trying to plot the frequency spectrum of a QPSK signal

binary_data = qammod(binary_data,4).*exp(1i*-pi/2);

Here, binary_data is my QPSK signal after I've used the 'quammod' function.

As you know, my binary_data consists of complex numbers. So how to plot its spectrum?

I used to plotting the signal which consists of real elements, not complex ones.