ADS lumped elements for higher frequencies/modes

Dear all,
I would like to simulate an antenna using ADS and lumped elements. The problem is I get only two resonance frequencies despite that the antenna simulated with CST has four resonances. I doubt that it is because of the equations I am using to get the lumped components values they are dependent of the frequency of operation could be that the issue if so How I can fix this ?
Any ideas or suggestions are more than welcomed

Are you sure that the difference between CST and ADS is because of using lump-elements? I guess CST considers lump elements as ideal elements(like what ADS does).

hi Nano_o,
its weird problem you facing. what is the frequency step size you using for ADS simulation? reduce the step size to get more data points so the results will match your CST.

BR
pragash

to verify the cause of disappearance of two resonance frequency, 1st simulate the imported touchstone file or layout without lumped component. if the results matches your CST, than probably you lumped element makes two resonance disappear.

Dear all,
thank you for replying to my question, actually I am trying to simulate the equivalent circuit of the antenna using ADS, in order to compare the results. The formula that I am using allow only to get the lower resonances,How I can get the resonances at higher frequencies ?
thanks once more!

hi Nano_o,
i need more information in order to help you. you are doing EMDS/Momentum simulation in ADS to compare the results with CST simulation for your antenna. Am i right?

what equation you are using in ADS to create lumped component? is this lumped element matching components for the antenna?

Hi pragash,
first, thank you for your time and interest I really appreciate it.
I am trying to build the schematic using RLC elements.
the expressions that I am using are depicted in the picture attached.
As you can see they dependent only on the antenna dimension, I believe that it is why I have this problem. Any suggestions?!

Hi nano,
so you representing antenna structure in CST with lumped element in ADS. am i correct? antenna structure means physical antenna with conductor material and etc. you trying to correlate between equation (ADS) and EM simulation (CST).

this equations created by you? if yes, how did you come out with this equation?

most probably it caused by inaccuracy of this equations in representing the antenna (provided your frequency step size in ADS is small enough). ADS simulation is straight forward so i doubt you have done mistake in that.

are you using ideal component or vendor component libraries/RCL in ADS? if you are using RCL/vendor component libraries, make sure that SRF of the components much higher than resonance frequency of the antenna.

Hi pragash,
Yes that is what I want to do.
Concerning the equations I found it in the literature. they work very well for lower frequencies which leads me to think that I need to add components to my schematic that are dependent only on frequency so I can have the resonances at higher frequency, but as far as I know when the frequency become higher it is difficult to model such a behavior. Any ideas on this matter?!
for the components, I am using the ones from ADS library but they don't have / I could not found where to check the self resonance frequency (SRF).
thank you very much for your help I really appreciate it!

[QUOTE=Nano_o;1480761]Hi pragash,
Yes that is what I want to do.
Concerning the equations I found it in the literature. they work very well for lower frequencies which leads me to think that I need to add components to my schematic that are dependent only on frequency so I can have the resonances at higher frequency, but as far as I know when the frequency become higher it is difficult to model such a behavior. Any ideas on this matter?!

You are right. Every lumped component has SRF. For frequency well below SRF, inductor will be inductor and capacitor will be a capacitor. After SRF, the capacitor will become/behave as inductors and the inductor will behave as a capacitor. There will be huge variation in inductance (for inductor) and capacitance (for the capacitor) when its closest to SRF point. That's why its preferred to select lumped component with SRF way above operating frequency.

ADS components which you select from lumped component tap are ideal components meaning those component does not have SRF. ideal component will behave the same over infinite range of frequency. so your issue should be in the equation you inserted. it has nothing to do with SRF.

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