I have the same problem. For high pass filter, I have to use series capacitor. This capacitors cannot be implemented using distributed elements. Therefore, we have to use lumped capacitor or MOS capacitor. These days, I am working on MOS capacitor model in HFSS.

regards,
lkuzu

Hi,
if you want to design correct microstrip filter try with "filter synthesis program" (like Serenade,Microwave office),this is
very simple way.HFSS is very good  only for 3D simulations,I think that it is unduly to use 3D simulator for microstrip filter.

designing a hbf is inverting the g values in lpf, the inductance become capacitance and vice versa  and we will have actual capacitance values expressed in picofarads and microstrip lines .there is a very good worked example for a hpf in the book(microwave solid state circuit design) by inder bahl & prakash bhartia page(258-259)

suhair al-ali

It is possible to get a series capacitance by running two microstrip lines close together, however the amount of capacitance attained is small. To increase this capacitance each side is of the microstrip line is "forked out" with the tongs of the fork interleaved. This method increases the area of interaction and thus increases the capacitance. More commonly chip capacitors are used to minimize valuable circuit space.

A shunt inductance will need access to the ground plane. This can happen by designing your filter near the edge of the circuit board or through via holes that drill through the substrate.

See pp.398 of "HF Filter Design and Computer Simulation" by Randall Rhea (of Eagleware fame).  Antoher approach is to use a structure consisting of high impedance series lines with low impedance shunt shorted stubs.  This is actually a wide bandpass structure (>50%) and is often referred to as a "pseudo-highpass" filter.

Is it such a problem?? Try to simulate in ADS normal microstrip notches plased side by sides, tuned to proper frequencies and You will get BPF, LPF,HPF, whatever You want. Every thing will depend on quantity, spacing and matching of notches.

Good luck,
Buding.

well i think  hight pass filter can be easly designed by using modefied SSL technology'Suspended Stripline technology', well i would recomend you to read a paper for Mr.W.Menzel:A Novel Suspended Stripline Filter.

he could could design a Filter with series capacitance and parallel inductunce.