PLL based frequency synthesizer

I want to design pll based frequency synthesizer for a frequency 2 GHz.Pleaese guide me how to design.

I have develop fixed oscillator using BJT. How I can convert it into VCO.

Probably the simplest way to convert your fixed frequency oscillator in a VCO is to replace the tuning capacitor with two varicaps.
Here is an example:
http://www.eetasia.com/ARTICLES/2002...MSD_EDA_AN.PDF

Within designing the pll based the frequency synthesizer, the low pass filter is very important.A bandwidth accelerates acquisition and ensures low phase noise further away from the carrier frequency.A narrow bandwidth tokerates larger disturbances in the pll and thereby maintains better synchronization.In the practical cases,the bandwidth of the loop filter is set to approximately one-tenth the reference frequency.

cjg40 have right....
try http://www.national.com/appinfo/wireless/ and use easypll soft if you want to design a programable vco using a pll
national is the best in pll design in my opinion...i designed a vco using lmx2316 and I can tell you it was very easy to do this with national tools (online tools)

you can design a synthesizer with peregrine's pe3336 or national 's lmx23X6 series and it's easy to design them.if you have no special requirement you can use passive LF filter . it's economical.

it is simple ,one pll ,two pll ,you will make synthesizer.
it is easy ,just for simple synthesizer..:)