Coupled line filter ADS simulation.

Hello,

I am desinging a parallel-coupled wideband bandpass filter. The requirements are showed in below:
Center freq:10 GHz
3dB BW: 1.5 GHz
low-pass prototype: 5-order Chebyshev with 0.1 dB ripple
material: RO3010 er=10.2 thickness=0.025'' and 1oz copper

I calculate the Ze and Zo myself, and then I use the tool ''LineCalc'' of ADS and also the Ansoft designer to get the W,S,L respectively. But the simulation in ADS is not what I want. Plz see the figures below. The center freq is at about 9.3 GHz, not at 10 GHz. I have double checked all the parameters for the RO3010. Could anyone tell me how can I improve the filter design to get the 10 GHz center freq?

Thanks in advance.

-Durant

Reduce the coupler lengths.

this is to account the edge fringing caps.

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Thanks. I will try this.

-Durant