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April 9, 2024 at 4:40 pmjeong hee yunSubscriber
As a result of wavelength sweep using the S-parameter of FDTD simulation, the following results were obtained. I have seen other people change their s-parameter results to abs^2 and plot them, and I have done the same.Â
1. What is the purpose of changing to abs^2?
2. Also, when plotting abs^2, should I use 10log or 20log? -
April 10, 2024 at 5:16 pmGuilin SunAnsys Employee
1: As you know, S is amplitude parameter. So abs^2 is the intensity/power parameter. For 2X2 device, abs(S11)^2 is power reflection and abs(S21)^2 is the power transmission for the specific mode.
2: if you want to get result in dB, for abs^2, it is 10log10. for abs(S), it is 20log10.
BTW: you mentioned you sweept wavelengh in FDTD? in the port/mode case, once you use broadband, you do not need to sweep since FDTD can give you broadband result from one simulation.Â
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April 11, 2024 at 4:24 pmjeong hee yunSubscriber
When converted to abs^2 value, what exactly should I write as the y-axis name?
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April 11, 2024 at 6:06 pmGuilin SunAnsys Employee
As mentioned previously, abs^2 is power or intensity quantity, and since it is already normalized, you can label it as transmission/reflection of the specific mode. When we say S parameters, they are always associated with modes. In broad definition, plane wave, Gaussian beam and waveguide modes are all "modes".Â
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- The topic ‘The meaning of abs^2 in S-parameter’ is closed to new replies.
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