How about set the pull-up components as an inductor parallelled with a resistor for example 50 ohm. Choose the inductor value big enough at the working frequency to make the parallelled impedance is almost same as the resistor. And this added inductor will remove the DC voltage drop which could guarantee the output signal will have full voltage swing.
The PLL architecture is an effective approach to creating very linear ramping waveforms that are useful for radar applications. That being said, one consideration is how fast the ramp can change and still have the PLL track it. The loop filter needs to be able to allow the frequency to slew fast enough, and you need to take measures to avoid cycle slipping