Need help in designing Zeroth Order Resonator

[deathscythe23]

Hi,

Im using CPW transmission lines for my resonator. Both port 1 and 2 are matched to 50ohms. However I got very poor results for my s11. Does anyone knows the problem?

 

[biff44]

Your analyzer is broken? Because if the ports were matched to 50 ohms, you would have a "good" s11

 

[deathscythe23]

I doubt so. I was thinking if it is the resonator circuit that is causing the poor results. I have a interdigital cap and a meander line inductor linked to the lower ground plane. Could this be causing a mismatch?

 

[deathscythe23]

Hi,

I have attached my circuit layout for better reference. Operating freq to be set at 2.45GHz. However, my simulation results only give s11=-3.2~3.4dB and s22=-5.4~5.6dB. Layout 1 shows the circuit for the simulation. What can I do to improve the readings?

The interdigital is 8.7mm by 5.7mm and the 2 feedlines are 2mm by 9mm. Gap between the feedlines and interdigital cap is 0.3mm. Meander line inductor is 4mm in length with 0.3mm for the width and 0.5mm for the spacing and lead length.

 

[biff44]

You are going to have to explain some more. First, that looks a lot like microstrip. Why are you calling it coplanar waveguide? Also, are there really gaps between the interdigital structure,and the transmission line to the right and left of it?