I recently done the project of designing CPW passive elements for 2-5 GHz , can any one tell me what should be the s-parameters of a resistor , should it be like low pass or what ,
It is better to consider that the equivalent circuit of a real resistor as being the resistor itself plus some series inductance plus some parallel capacitance.
These parasitics probably can't be ignored at 2-5 Ghz. They will also be dependent to some extent on just how the resistor is soldered onto the PCB and the shape of the pads and properties of PCB.
So if you want the best accuracy you'll just have to measure them up on your VNA !