Design and implementation of VCDRO

Hi every body.
I am implementing an X-band VCDRO.
I would like to know what is the maximum freq. variation range of a typical X-band VCDRO.
Please recommend a method to have variation range more than 100 MHz in the center Freq. of 9 GHz.
I want to design a PLL which it's VCO is made of DRO.
The target of my design is to reach a phase noise of 120 dBc/Hz at 10 kHz.
Any paper or ebook from you is helpful for me.
Thanks,
Razavipour.