Thanks...Yes the driver is indeed a bipolar driving the power MOSFET. However, I was just reading the manual now and there it is written "The RF driver buffers the signal and produces a suitable square wave signal at the carrier frequency capable of driving the power amplifier".
The RF driver shown is basically two bipolar transistors in push pull configuration. I am confused, can a push pull configuration work with square waves? IN that case the driver would be working more as a switch rather than an amplifier...wont it?