Questions tagged [waveguide]

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Two Dimensional Hodge Decomposition

In deriving the equation governing propagation of wave in a wave guide, a specific form of Hodge decomposition theorem is used. The Hodge decomposition theorem applied in two dimensions allows us to ...
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Why do we use wires/conductors to transport energy?

I am currently studying Maxwell equations and I learned that copper wires are essentially just wave guides for EM waves. Why do we not use an insulator to guide the wave and transport the energy which ...
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How are the Boundary conditions for wave guides derived?

So I understand that for a linear material we get the equations where 1 is the material above a boundary and 2 is the new material below the boundary. $$E_1^{\parallel} - E_2^{\parallel} = 0 $$ $$\...
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TEM waves in waveguides and free space

I have seen the mathematical explanation as to why TEM waves cannot exist in hollow waveguides (eg: https://www.youtube.com/watch?v=G8u2WEBF7MY), But that derivation holds good for plane waves in free ...
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Why is the curl of electric field vector inside a hollow waveguide zero for TEM waves?

I have been studying David Griffiths 'Introduction to Electrodynamics', Electromagnetic Waves chapter. For hollow wave guide, the Maxwell's equations $$\begin{align} \nabla\cdot\mathbf E &= 0 \\ \...
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How to get single mode propagation using the Wave propagation method?

I am trying to simulate single mode waveguide using wave propogation method but when launching the beam inside I get the Tablot effect (like in MMI). I have adjusted the refractive indexes and the ...
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Steven Weinberg says $L$ is the fundamental EM wavelength in a cubical cavity $L^3;$ not the typically asserted $2L.$

This is from Steven Weinberg's Lectures on Quantum Mechanics, 2nd Ed., page 2: For instance, for a cubical box of width $L,$ whatever boundary condition is satisfied on one face of the box must be ...
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How is certain area of waveguide becomes visible to user?

I was reading an article and came across this image As shown, image becomes visible to eye after reaching a specific area of the glass. But how does it work? Why is it being reflected at such a weird ...
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Waveguide conditions [closed]

Waves in a ideal waveguide have to satisfy that $E_{\parallel}=0$ and $B_{\perp}=0$. Because of the continuity conditions I would think that this relates to the surface. But the solution says that $E_{...
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Why dielectric waveguides support hybrid modes and metallic waveguides don't?

Can anyone explain me qualitatively, why dielectric waveguides (core and infinite cladding) support hybrid modes ($E_z$ and $H_z$ components in the guided wave) while metallic waveguides cannot. I am ...
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Field at exactly the cutoff frequency of a waveguide

What happens below or above a cutoff frequency is very well documented! I have never seen though a clear explanation (as a matter of fact no explanation) about what happens at exactly the cutoff ...
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Why light radiates out of the bend in dielectric waveguides?

Why EM wave radiates out of the waveguide. Is this similar to centrifugal force?
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Approximately calculating structure of modes in a waveguide

I know this a super open-ended question, but I hope I can get something out of it anyway. Here is a crude diagram of the cross section of a waveguide I am simulating on COMSOL: and here is the output ...
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What are eigenfrequencies of guided electromagnetic waves?

I am using a commercial software (COMSOL) to find modes in dielectric waveguides. Each mode is associated with an eigenfrequency. In this context, what is an eigenfrequency?
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Sharing one propagation constant in circular waveguide

I need to know more about this sentence for circular wave-guide structure: "When mode degeneration occurs, two modes sharing one propagation constant may be linearly combined. There are two ...
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What causes the undistorted propagation of picosecond THz pulses not to be possible for circular waveguides?

When reading about the concept of circular waveguides, I came across the following statement that I am struggling to undertand. "(...) for circular waveguides the undistorted propagation of ...
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How to model total internal reflection in waveguides?

I was trying to solve a slab waveguide numerically using finite elements, but I could not figure the correct boundary conditions between the two dielectrics to force evanescent waves in the cladding ...
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Optical Waveguide Mode Profile

SE, I have a question about a mode profile chart from Synopsis RSOFT. After following an example silicon Y-Splitter waveguide below with the waveguide width = 0.45um and height=0.22 um , I simulated ...
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Electromagnetic wave in a coaxial transmission line

I am currently working on [Introduction to Electrodynamics] of David J.Griffiths, chapter 9.5.3. The book says: In the coaxial transmission line of inner radius a and outer radius b, TEM modes are ...
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What is a resonance element?

I'm looking at a horn antenna and why its a good addition to a waveguide. I've read that the horn can operate at a wide range of frequencies since it has no resonant element. But I can't find a good ...
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Wavelength of light in a waveguide

I've done a derivation showing that the wave length of light in a waveguide is longer than that of free space light. But I don't really have an intuitive understanding of why this is. I think my prof ...
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Wave impedance experiment using a wave guide

I am conducting an experiment to reduce wave guide impedance. To do this, I have a wave guide emitting microwaves down the tube then into free space. A oscilloscope is connected to a to a standing ...
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Wave impedance in a wave guide

I'm trying to get a better understanding of impedance for a wave guide. First of all, my current understanding of the topic is that its a ratio of the electric field amplitude over the magnetic field ...
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Derivation of wavelength in a waveguide

I'm trying to derive this expression for the wave length in a wave guide. I'm following this derivation from the Feynman lectures https://www.feynmanlectures.caltech.edu/II_24.html#Ch24-F4. I do not ...
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Waveguide cut off frequency derivation - Wave equation to Helmholtz equation

I'm trying to derive the cut off frequency for a wave guide. I found a derivation on wikipedia, but I don't understand the first step where we go from the wave equation to the helmholtz equation. Why ...
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Wave guides and induced free charges and currents

Consider electromagnetic waves confined to the interior of a hollow pipe or waveguide. Assuming that the waveguide is a perfect conductor so that electric field and magnetic field inside the material ...
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Waveguide boundary conditions

I am calculating useful band width for the case of half circular waveguide with radius a, filed with plasma with $\epsilon=1-\omega_p^2/\omega^2$, booth for transferse electric (TE), and transferse ...
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Effective refractive index can be equal zero?

Can someone please explain the cases that the Effective refractive index $n$ on it can be equal zero? Does such a situation even exist? I am trying to solve an ordinary differential equation to find ...
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In a rectangular waveguide, how can one determine if any propagation modes exist?

I'm currently studying microwave engineering, and I came across the query mentioned above. I know that rectangular waveguides use TE(m,n),TE and TM modes, but I do not understand how these modes came ...
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Why the fields of the quasi-TEM mode of microstrip line tend to concentrate in the dielectric as frequency goes higher?

A microstrip line is a waveguiding structure as shown below: Because of the inhomogeneity, the fundamental mode of propagation is a quasi-TEM mode, which means that the z components of the E and H ...
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Waveguide modes: does a particular mode only propagate for one particular frequency?

I am trying to understand modes in a cylindrical dielectric waveguide. Does a particular mode only propagate for one particular frequency? Or, does a mode exist simply as long as the signal is above ...
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Rectangular waveguide vs. sloped-wall waveguide

Can anyone recommend a book or paper where they compare a trapezoidal waveguide (angled wall) with one a rectangular waveguide? I have been searching a lot with no success.
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Electric and magnetic fields boundary conditions

For a perfectly conducting and perfectly dielectric interface, I understood that tangential component of electric field is zero and continuous. But I have read that the normal component of magnetic ...
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Dominant mode in rectangular waveguide

for a standard rectangular wave guide, which a > b (horizontal dimension > vertical dimension), the dominant mode is supposed to be TE10/TM10 mode. If we flip the direction, make b > a (...
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Whats the frequency of the modes in a waveguide?

I have been able to confuse myself: I am studying the form of the modes in a rectangular waveguide: I understand that each mode has a different spatial distribution, but what I dont understand is if ...
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Dielectric material in a Waveguide

I'm in the middle of an experiment and before my final measurement I want to find out the electic properties of the material i'm working with. The question is: If I have a metallic waveguide and I ...
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Does absorption in the cladding material change the real value of the propagation constant of a waveguide?

Imagine two scenarios: two cladding materials with the same real refractive index, but one has absorption while the other does not. Now, these materials act as the top cladding of a waveguide (for ...
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Half sphere in waveguide

So, the cutoff freq, $f_c$ of a rectangular waveguide is following: $$f_{c}=\frac{1}{2\pi\sqrt{\mu \epsilon }}\sqrt{(\frac{\pi}{a})^{2}}.$$ For TE10 mode, the equation is a little weird as I am ...
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Cut slit on waveguide [closed]

Say I have a waveguide operating on TE10 mode, as following, I need to cut a slit on the waveguide so wave can radiate. Where Should I cut the slit? I assume since TE10 mode the standing wave is ...
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Waveguide operation frequency range

Google told me the operation frequency is 125% - 190% of the cutoff frequency. But I did not find any other material for reasoning. My question: What happens if frequency was too high?
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Cutoff wave-number in wave-guides

When defining the dispersion relation in a waveguide we have an equation that also includes a cutoff wave-number. This cutoff wave number depends on the geometry of the waveguide. $$ k_z = \sqrt{\...
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Inhomogenous wave equation: Waveguiding vs radiation problems

I want to ask a general question about two vast topics of applied electromagnetics: Guided and unguided (radiated) waves. I have noticed that there are almost always some common strategies for ...
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Understanding guided and non-guided modes in a waveguide

Usually, an optical waveguide is considered in the following way. We have a plane wave traveling inside the waveguide at a certain angle $\alpha$ (which corresponds to the direction of the wavevector $...
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Validity of flat coupling approximation in input-output theory + why is it called Markov approximation?

In standard input-output theory, we model the interaction between light and a two level system by the following hamiltonian which assumes rotating wave approximation: The interaction between a ...
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Can a metallic rectangular waveguide support hybrid modes?

Studying the basics of guided waves in metallic rectangular waveguides, filled with homogenous dielectric material, I see that there is always a distinction between TE and TM modes. I understand that ...
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How is magnetic flux viewed in QED?

I know that QED is formulated in terms of Lagrangian density. So when we solve for a physical system we ultimately ends up finding $\psi$ and $A_{\mu}$. I'm not interested in $\psi$ for now. Since I ...
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Magnetic Field Distribution in TEM (TransverseElectroMagnetic) Modes

in many books (Electromagnetics, M. Notarov; Foundations for Microwave Engineering, Collin; Microwave Engineering, Pozar etc) I have read that in a certain waveguide or transmission line, the ...
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Why is the magnitude of the electric field dependent only on $x$ and $y$ coordinates?

So I am reading a book on electromagnetism and in it they are assuming that the magnitude of the electric field is dependent only on $x$ and $y$ coordinates in a waveguide and I wanted to know why ...
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Is there a subterranean SOFAR channel

After discovering the SOFAR channel in water at a depth which the speed of sound is at its minimum and acts as a waveguide, it was postulated that a similar channel existed in the atmosphere and ...
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Electric field pull on EM wave due to copper trace wave guidance

My background is electrical engineering, but I have a physics related question. An AC signal is guided by electric copper pairs, one a trace, the other a reference plane. I read that the EM wave ...
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