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What is the expression of the instantaneous electric field, normEi?
Posted Mar 30, 2018, 11:58 p.m. EDT RF & Microwave Engineering Version 5.3a 1 Reply
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Dear all, I am using RF module, frequency domain study (2D model). I try to plot out the electric field images, I know emw.normE=sqrt(Ex^2+Ey^2). However, when I type in expression emw.Ex^2+emw.Ey^2, the results are different. What is the difference between these two?
And what is the expression of the instantaneous electric field, normEi?
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The reason the two results are different is that in the frequency domain, the electric field is represented as a COMPLEX quantity. That is, the components emw.Ex, emw.Ey, and emw.Ez are all complex numbers. The variable emw.normE is the magnitude of the complex vector. This magnitude is fixed, as the phase varies. When you plot (as opposed to compute with, in an expression) a quantity such as emw.Ex, you only see the real part in your plot. But if you multiply field components together, Comsol multiplies the complex numbers together. So you have to be careful about doing that. You can also work with the real or imaginary parts alone, if you wish, when doing computations, by using these kinds of expressions: real(emw.Ex) or imag(emw.Ex), etc. I hope that helps.
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