How to generate IQ samples of a signal?
The reason one uses a complex signal at baseband is so that one can distinguish between positive and negative frequency...otherwise, when the signal is mixed to a higher frequency, it will have two identical sidebands, taking up twice the spectrum.  Without knowing what you're modulating, I can only offer general advice...take your real baseband signal taking up bandwidth 0..Fmax, and multiply it by exp(2*piiFmax/2*t) (note the 2s cancel out, but the form is more recognizable).  This will heterodyne it down to a complex signal occupying -Fmax/2..Fmax/2, and that can be passed to the RF chip.