spectrum of QPSK baseband block

simulink:i use the baseband QPSK modulator block, and try to see the spectrum.In the beginning I have a random integer block wiyth a smapling frequency of Fs. This is followed by baseband QPSK modulator and then a spectrum. However, the spectrum is just a flat line and has nothing to do with the real QPSK spectrum. Even when I increase the sampling frequency to 2Fs on the spectrum analyzer, the spectrum is doubled, and see no sidelobes whatsoever. This is not the spectrum of QPsk SIGNAL, COULD SOMEONE LET ME KNOW WHY THIS IS HAPPENING? This is quite important as this blpock does not represent the real QPSK spectrum and therefore, cannot see any spectral regrowth when using a PA. Thank you