DCA1000EVM: The doubt about the "sample rate" and "sample point" in the mmwave studio

Are the "sample rate" and "ADC samples" used for modulating the IF signal or the transmitted/received chirp？I think if these 2 configuration are used for  transmitted/received chirp, it may need the "sample rate" to be 2*(77GHz~81GHz)  according to the Nyquist sampling theory. But the max value of the "sample rate" is 27.5MHz in the AWR1843 sensor, for which I think they are used for the IF signal. Am I getting this wrong?