Why Is There a Negative Sign in the Modal Impedance of TEn Mode?

AI Thread Summary
The discussion centers on the negative sign in the modal impedance of the TEn mode in a parallel plate waveguide. It highlights the connection between this negative sign and Maxwell's equations, which relate the electric and magnetic field components. The negative sign is necessary to ensure that the wave impedance remains positive. Participants seek clarification on whether this aspect relates to the reflection coefficient. Understanding this concept is crucial for accurate analysis of wave propagation in such structures.
Brianrofl
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Hi, I'm working on a parallel plate wave guide for wave propagation and had a question about it. Here's a quick diagram:

Capture.PNG


While analyzing an EM field polarized in the y-direction, the modal impedance of the TEn mode comes out to be:

Capture.PNG


Why is that negative sign there? If someone could just explain where that negative sign comes from I'd appreciate it greatly. Does it have to do with the reflection coefficient?
 
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Brianrofl said:
Hi, I'm working on a parallel plate wave guide for wave propagation and had a question about it. Here's a quick diagram:

View attachment 97051

While analyzing an EM field polarized in the y-direction, the modal impedance of the TEn mode comes out to be:

View attachment 97052

Why is that negative sign there? If someone could just explain where that negative sign comes from I'd appreciate it greatly. Does it have to do with the reflection coefficient?
You have to go back to Maxwell's equations to get the relation between components of the electric and magnetic fields. In order to get the wave impedance positive the minus sign has to be used.
 
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