what's the 1.2GHz video transmitter IC

And the reason for that would be that there are only license free ISM bands for such things at 2.4 GHz or 915 Mhz. Do you have a license in your country to transmit at 1.2 GHz? If not...I suggest changing your frequency plan.

FCC says that it is not allowed for general public, but it is ok to build and use if you are a licensed radio-amateur. This ATV band covers from 1240-1300 MHz.
A common VCO/modulator in this type of equipment is Z-Communications CLV1137A-LF, which then is mixed up to actual tx frequency.

In that case, just use an ADF4350, and analog FM modulate the VCO