Re: RF SYSTEM
To be an RF System Engineer you have to be very familiar with all RF circuit blocks (LNA, Mixer, IF amplifier, IQ demod/mod, PA, Antenna, etc), but also you have to have knowledge about interactions between RF circuits and Digital circuits (A/D and D/A converters, DSP, microcontrollers, etc).
RF System Engineer has to know how to do the characterization of each RF circuit block, or for multiple blocks working together.
From my opinion a good RF System Engineer shall be a good RF Circuit Designer before.