S-parameters simulation results' difference

[pYrana13]

Hi all,

I made a circuit with LC tank resonator as shown below without any microstrips element and the result of S-parameter shows a resonant amplitude at 1GHz ( f_res = 1/2*pi*sqrt(LC) ). When I integrate microstrip lines into the schematic, the S-parameter result now shows an attenuation at the resonant frequency of 1 GHz. (Using LineCalc of ADS, i got line width of 1.1186mm for Z0 = 50 Ohm at 1GHz. )

Where did I do wrong here?

 

[RealAEL]

You haven't done anything 'wrong'. Adding layout parasitics will always alter the performace of a circuit unless lengths are zero, which gets you back to the ideal circuit with no layout. With this substrate 20mm of interconnect around any trace will be equivalent to over 30degrees of phase shift. You need to design the circuit to work with these distributed transmission line effects, maybe tuning and opinizing the lengths of the transmission line to get the performance back to what you require.