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RF (temw) - emw.rGaindBEfar Issues
Posted 28.08.2020, 19:26 GMT-4 RF & Microwave Engineering 4 Replies
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I am having issues using the Global Evaluation function emw.rGaindBEfar. I receive this error. Any direction to overcome this problem would be greatly appreciated,
Undefined variable. - Variable: x - Global scope Illegal destination coordinates in convolution integral kernel. - Operator: EfarxEfaryEfarz - Global scope Failed to evaluate expression. - Expression: Efarx(x,y,z) Failed to evaluate expression. - Expression: abs(Efarx(x,y,z)) Failed to evaluate variable. - Variable: comp1.emw.normEfar - Defined as: sqrt(((abs(Efarx(x,y,z))^2)+(abs(Efary(x,y,z))^2))+(abs(Efarz(x,y,z))^2)) Failed to evaluate variable. - Variable: comp1.emw.rGaindBEfar - Defined as: 10log10((unit_ohm_cf(5(comp1.emw.normEfar^2)))/((abs(unit_V_cf)^2)3)) Failed to evaluate expression. - Expression: comp1.emw.rGaindBEfar
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- I encourage you to post your model to the forum, so others can look at it and help you find your problem.
- Have you worked with far-field calculations in Comsol models successfully before? If not, bear in mind that you need to define certain volumes and surfaces to use in this kind of calculation, since the computed far-field quantities depend on integrals over those previously-specified surfaces. Did you properly specify those? If not, then that is likely your problem.
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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I have I actually had the model working for the frequency domain but when I trainitioned to the time domain. I started receiving the error. This is my first time modeling a time domain pulse fed antenna. I have set my far-feild domain and boundaries. Im really scratching my head.
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Oh. To my knowledge, Comsol has not implemented time-domain far field computations. I'd like them to add that feature! To do so, they will need to prepare/include a time-domain version of the Stratton-Chu far-field formulation (which involves evaluations of integrals of the time-derivatives of the surface fields, evaluated at retarded times). Note to Comsol, if you are reading this: If by some wild chance you don't already know/understand all the math/physics and equations to implement that (but I bet you do!), just email me and I will send the key info to you! You know where to find me!
:)
Added: You may notice that in your model, where you specified the far-field boundaries, Comsol has a note that says " Far-field calculation requires Time to Frequency FFT study step." I haven't used that, but if I understand it correctly, the idea is to compute frequency-domain far fields in post processing of models that were solved in the time domain. That is, of course, not the same thing as computing an actual radiated far-field time-domain waveform. To do that, I would encourage Comsol to implement the time-domain version of the Statton-Chu formulation, as I noted above.
-------------------Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
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Ahhh this makes since I will add the Time to Frequency FFT. I totally overlooked that. You have been incredibly helpful. I will have to take a look at the Stratton-Chu far-field formulation sounds interesting.