FPGA implementation of UHF transmitter in airborne applications

I think you are not likely to succeed if you need us to tell you what blocks you need. Having a block diagram is a starting point, but is also probably the easiest step to the whole process. You also didn't mention anything about modulation.

To paraphrase:

If you don't even know the basic blocks of a UHF Transmitter you are unlikely to succeed without some personal research. [I heartily concur]

Cheers

PeteS