How Does Phase Shift Affect Resonant Frequency in PEC Cylinders?

Click For Summary

Discussion Overview

The discussion revolves around the relationship between phase shift and resonant frequency in perfectly electrically conducting (PEC) cylinders when illuminated by a plane wave. Participants explore the relevance of surface current phase in understanding resonance phenomena, particularly in the context of a frequency sweep experiment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant describes an experiment involving a z-polarized plane wave illuminating a thin PEC wire, noting that resonance is expected when the wavelength is twice the length of the wire.
  • Another participant suggests that understanding the phase of the surface current is crucial for grasping the resonance phenomenon, prompting a deeper inquiry into the interaction between the wave and the PEC.
  • A participant reports that at the resonance frequency, the phase of the surface current is 180 degrees, indicating a potential relationship between current phase and resonance.
  • Further discussion raises questions about the behavior of the current phase as the frequency deviates from resonance, with one participant noting that the phase continues to increase beyond 180 degrees.
  • Participants are encouraged to think about other resonant situations that may exhibit similar phase behavior, particularly in relation to the concept of phase in radians.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the relevance of phase shift to resonance, with some agreeing on the importance of examining the phase of surface currents while others seek clarification on its implications. The discussion remains unresolved regarding the exact nature of the relationship between phase and resonance.

Contextual Notes

There are limitations in the assumptions made about the experimental setup and the definitions of resonance and phase shift. The discussion does not fully resolve the mathematical implications of phase behavior as frequency changes.

Who May Find This Useful

This discussion may be useful for those interested in electromagnetic theory, wave interactions with materials, and resonance phenomena in physics and engineering contexts.

fereshteh
Messages
4
Reaction score
0
So I have this PEC cylinder that I am illuminating with a plane wave. As we know it should resonate when lambda is twice the length of the cylinder.
My adviser suggested to examine the phase of surface current, but I do not understand how it is relevant. Maybe I didn't get it right...
 
Engineering news on Phys.org
Welcome to PF.
It helps to describe the experiment setup - do not assume everyone knows the same exact setup that your course uses.

Did you examine the relative phase of the current anyway?
To understand what the phase has to do with it, consider how the wave you are using interacts with the PEC: why would you expect resonance of any kind at all anyway?
 
You are right. I should try to describe it.
I have a plane wave, z-polarized, illuminating a thin PEC wire along z-direction.
I am doing a frequency sweep in such a way that the wavelength corresponding to central frequency is twice the length of the wire. So at that frequency we should see bigger RCS due to resonance. My adviser mentioned I should examine the phase of the surface current on PEC to show this resonance at this frequency but I do not understand how this is relevant.
 
I did examine it. At the resonance frequency it is 180 degrees.
 
fereshteh said:
At the resonance frequency it is 180 degrees.
OK. So clearly there is a relationship between the current phase and resonance.
(Did you check what happens to the current phase as you went off resonance?)
me said:
To understand what the phase has to do with it, consider how the wave you are using interacts with the PEC: why would you expect resonance of any kind at all anyway?
 
It just continues to increase!
 
What? Is it always greater than 180 degrees?
(That would be pi radiens - hint: useful to start thinking in radiens.)
Can you think of other resonant situations which behave like this?
What do you think happens at 2[itex]\pi[/itex]?
 

Similar threads

Replies
2
Views
3K
Replies
1
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
4
Views
3K
Replies
5
Views
2K
Replies
1
Views
3K
  • · Replies 1 ·
Replies
1
Views
13K
  • · Replies 13 ·
Replies
13
Views
900
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 41 ·
2
Replies
41
Views
8K