Hi all

I am designing a double cross-coupled LC CMOS VCO for GSM900. I am trying to figure out a way to determine the W/L ratios of the two pairs of cross-coupled PMOS and NMOS transistors. I would like to know what factors I would need to take into account while doing this. I did look a lot of papers presented but they all dealt with phase noise and design of the tank circuit. Are there any design equations to obtain the width and length..?

Any help would be greatly appreciated.