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What is the difference between attenuation and insertion loss S21 in HFSS?

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x529

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In HFSS, the attenuation constant is solved: by the equation re(Gamma)/1000*8.686 (dB/mm);
Does the attenuation include radiation losses?
The S21 is bad, however the total attenuation have good profermance. I dont know the reason, who can help me?
What is the difference between attenuation and insertion loss S21 in HFSS?
QQ图片20210903183847.png

QQ图片20210903184948.png
 

PlanarMetamaterials

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The attenuation constant you've provided is a modal property; is is determined solely by the transverse cross-section of the medium through which a given wave propagates. It can only be applied properly under the assumption that the medium is longitudinally invariant. This could include radiation, but usually doesn't.

S21 (or insertion loss, in a two-port network) on the other hand, measures the degree of voltage and/or power that comes out of port 2 of any (necessarily finite) network given a certain amount into port 1. This is regardless as to what is inside the network.

In simple systems like a waveguide, S21 is roughly proportional to the attenuation constant.
 
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x529

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The attenuation constant you've provided is a modal property; is is determined solely by the transverse cross-section of the medium through which a given wave propagates. It can only be applied properly under the assumption that the medium is longitudinally invariant. This could include radiation, but usually doesn't.

S21 (or insertion loss, in a two-port network) on the other hand, measures the degree of voltage and/or power that comes out of port 2 of any (necessarily finite) network given a certain amount into port 1. This is regardless as to what is inside the network.

In simple systems like a waveguide, S21 is roughly proportional to the attenuation constant.
Thank you.
When a novel transmission line is proposed, the article analyzes the attenuation constant first, or the attenuation constant and S21 are analyzed at the same time in some papers.

S21 (insertion loss) does not correspond to attenuation constant, as shown in the figure, it maybe caused by radiation. To better measure/describe the device (like transmission line ) characteristics, which parameter is more accurate? attenuation or S21~
Waiting your reply~
 

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S21 will take into account all possible sources of loss, so it's probably a better metric -- although, a good simulator would include various effects in the attenuation constant.
 
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