Questions tagged [waveguide]

A waveguide is a physical structure that guides electromagnetic or sound waves. They are most commonly employed at high frequencies such as microwave.

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How to prove the Maxwell's equations written using wave number vector? [closed]

I was studying the oblique incidence of a plane wave(EM wave) in a boundary and came across these forms of Maxwell's equations. First I tried to prove them by multiplying them(k×E or k×H) using their ...
183 views

How do I find out the dimensions of a rectangular waveguide given the frequency I want to operate it at?

I want to design a horn antenna to detect the 21 cm hydrogen line. I know how to optimize the antenna dimensions by taking into account some functions that approximate the phase errors and ...
1 vote
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Is there a standard that describes the term "coplanar waveguide"?

I look at IEC60050 "International Electrotechnical Vocabulary" standard at section 726 "Transmission lines and waveguides" and searching on the word "coplanar" gives me ...
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Why do dielectric waveguides support hybrid modes and metallic waveguides do not?

Can anyone explain to 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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Impedance of TE and TM waves in a rectangular waveguide

In a rectangular waveguide we have an impedance which is different for TM and TE waves. $$Z_{TE,m,n} =\frac{k\eta_0}{\beta_{m,n}}$$ $$Z_{TM,m,n} =\frac{k \beta_{m,n}}{\eta_0}$$ where  \beta_{m,n} =\...
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The field in a waveguide at exactly the cut-off frequency

Can anyone explain to me qualitatively, what kind of field exists inside a waveguide at EXACTLY the cut-off frequency? I would be grateful if an explanation was given about waveguides with metalic ...
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How can I tell whether a waveguide supports hybrid modes or not?

When studying metallic waveguides, it was taken for granted that the TE and TM (and potentially TEM) formed a complete set, that is, any electromagnetic field in the waveguide could be written as a ...
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468 views

I need help trying to set up a rectangular waveguide in HFSS,

Task: Setup a rectangular waveguide in HFSS using four perfect E boundaries on the side faces of a box and waveports on the end faces of the box. Set up your dimensions so that at the lowest frequency ...
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Where is the azimuth and radial direction on the mode plot

Hello the photo bellow presents TE01 mode. Where on the plot can i see the azimuth and the radial directions? Thanks.
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How to interpret waveguide multi-mode S-parameters in CST

I have a cylindrical waveguide which is excited with two modes in each ports as shown bellow. However I cant see the meaning of S-params shown bellow. photo one shows total isolation(-100dB) While ...
191 views

Why is a microwave oven equipped with a waveguide? [duplicate]

In a microwave oven, the magnetron connects to the waveguide.  Magnetrons produce microwaves, which are guided into the cooking chamber by waveguides. Why don't we directly connect the magnetron to ...
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1 vote
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Waveguides and optical fibres

Why at microwave frequency we prefer rectangular waveguides while at optical frequency circular waveguides (i.e. optical fibres). Can we have rectangular optical fibres.
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How to imagine the mathematical expression in the waveguide?

Below we see an example expression for the E-field. It has three components: polarization of the field propagation direction standing wave pattern In the photo below of the field "L" has ...
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410 views

What is a guided mode?

I am currently reading my text, for my electromagnetics course, and we are discussing guided waves. The text casually mentions the term "guided modes", and never really defines what that ...
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Different 50Ohm-matched condition for different length of metamaterial waveguide

Based on coplanar waveguide, I am designing a meta-material waveguide by inserting lumped-element inductors along the center line. Here are some parameters: Target frequency: 10-20 GHz Size of lump ...
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What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave-length long?

What is the impedance looking into a length of coaxial cable that is short-circuited at the far end and a half wave long? I have been told that this the the basis of what is known as a wave guide &...
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Dielectric slab waveguide

let's consider the so called dielectric slab waveguide (references for image and equations: here, page 53): I do not know much about it, I know only that it is a planar guiding structure which is ...
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Elliptical polarization and waveguides

It is known that a generic harmonic electric field which propagages in free space has an elliptical polarization (if you want to read the proof, look at this, slides 72 - 99). My question is: what ...
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Engineering very high impedance resonator with coplanar waveguides

I have very little knowledge of electrical engineering, so please understand if my questions are somewhat trivial. I have read that a coplanar waveguide (CPWG) acts as a lumped LC oscillator circuit, ...
1 vote
135 views

Can I get the S21 parameter from a one-port open, short and load reading?

I am currently working with a custom rectangular waveguide, which has one port abled to connect to a VNA,(call it port a) but the other side cannot, (its part of a bigger system but for now its only ...
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Designing waveguide based structure using cst

I am going to start designing waveguide based circulator , hybrid and loads using cst or ansys workbench. I am quite familiar with the design of microstripline and stripline based systems using ADS. ...
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Shape of waves in waveguide

What is actually going on in waveguide when the wave is passing through it ? If I am not mistaking , the plane waves are "fed" to the waveguide and there is a cutoff freq above which the waves can ...
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Evaluation of the dominant mode in a waveguide

In a waveguide, the dominant mode is defined as the propagation mode with the lowest cutoff frequency. Now let's consider a structure in which the lowest cutoff frequency occurs for two different ...
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1 vote
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Geometric spreading of an impulse antenna

I am new to radar and curious about the geometric spreading in free space. I set up an air-coupled antenna about a half meter above the ground, with a large PEC on the ground. Then I adjusted the ...
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235 views

Waveguides Equivalent Circuits

I was reading in a book how to derive the equivalent circuits for TE, TM, TEM modes of a generic ideal (without losses) waveguide. After some computations, it found this equivalent circuit for TE ...
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Cut-off frequency in ideal waveguides

it is known that in an ideal waveguide (with a perfect electric conductor and with non-dispersive and non-conductive dielectric) there is a cut-off frequency, for each mode, such that for higher ...
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164 views

Excitation of a resonant cavity

let's consider this picture in which a cylindrical resonant cavity is excited through a waveguide. I have some questions: 1) Why is it called "Magnetic Coupling"? I thought this excitation simply ...
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253 views

How to construct an SMA feedline for a horn antenna

I'm constructing an sma coax to waveguide transition for a horn antenna. Here's a cross-sectional view of what the device will look like I can 3d print the waveguide portion (I use a conductive paint ...
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Impedance mismatch vs Signal attenuation

I'm currently designing a 50Ω grounded coplanar waveguide (GCPW) which connects an antenna to an LTE modem. My question is: does there exist a standard graph/chart that attempts to generalise ...
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Calculating dielectric constant of a dielectric sample placed inside a rectangular waveguide [duplicate]

Im trying to calculate the dielectric constant of a dielectric sample placed inside a rectangular waveguide over a range of frequenices. I used WR90 ( X band ).Using the s parameter data (S11 and S21),...
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Can anyone tell me how to find permittivity of a dielectric sample using a rectangular waveguide

Im trying to find the material paramters of a dielectric sample using a waveguide(X band) employing the Transmission/Reflection technique. While performing simulation in CST, how to properly orient ...
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Guided propagation in transmission lines

Can you help me on understanding why we may say this transmission line the propagation is guided and there is not any radiation? It is a 2-conductors transmission line, in which the conductors are ...
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Considering Moding Issues in High Speed PCB Design

My question is a more generic one. I recently learnt about TE and TM propagation modes in waveguides. This made me think that when designing high-speed PCBs people always talk about matching the ...
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Radiation Source placement and waveguide parameters for Horn Antenna

I am designing ("arranging", actually) a horn antenna for a 77-81 GHz Radar. My module has a patch antenna which can't be placed inside the waveguide for some reasons. After the patch antenna, we have ...
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RF Design - Antenna Feed-line Parameters

I am implementing a BLE device with a chip antenna. The device has already been impedance matched to 50Ω and is ready to be connected to the feedline and antenna. The antenna datasheet has a ...
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What is the mode of a square waveguide $TE_{11}$ that is deformed into a circle?

I am trying to solve the 2013 paper set by ISRO for electrical engineers. I want some help to solve Question no 17 is correct. So I don't even know how to approach the problem, what will be the new ...
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Single-line power transmission of 1MW over 35,000km [closed]

This question posted on the physics stack exchange has not received much attention. I thought the audience here might be more able to answer it. Background A space elevator is mechanism to provide ...
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Differential Pair Reference Plane Coupling

I am routing LVDS pair on a flex board. The signal is 264MHz. I used Saturn PCB design to calculate width and spacing between conductors. The targeted impedance for diff pair is 100 ohms, which is ...
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2k views

Coplanar Waveguide Calculations PCBS, AppCAD v.s. Online calculators

So lately I noticed that the Coplanar Waveguid calculations of AppCAD (http://www.hp.woodshot.com/) did not give the same result as the online calculators do. https://chemandy.com/calculators/...
1 vote
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Frequency response of the waveguide

So, I have signal in the waveguide that is transmitted by two modes of radiation, for which the delay is for example $\tau_1=6\,\text{ns},\, \tau_2=6.5\,\text{ns}$, respectively. And the energy ...
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Design of cavity filter

I try to design a Chebyshev bandpass filter for 6 GHz as a coaxial cavity filter. I know that the filter can be designed with the aid of the coupling coefficients between the resonators and the loaded ...
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Metallic Waveguide Boundary

I've been studying TE and TM modes on waveguides for microwave frequencies. It basically consists on applying Maxwell equations on a rectangular metallic cavity, with infinite length on $z$ ...
3k views

Note I turned my answer into something of a collection of free impedance calculators.. I was thinking of using one of the most ubiquitous connectors in the world - 2.54mm pin header. The snag here is ...
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Can I trust these microwave power readings?

So I've got an old Hughes TWT that supplies roughly 20W across the Ku band (12.4 - 18 GHz) that has a waveguide output flange (WR-62). I am "gently re-purposing" it to be driven at a lower frequency (...
352 views

Rectangular Waveguide H-Plane Step Discontinuity - Equivalent Reactance for Change in Height

I have been reading Pozar's Microwave Engineering, and in Section 4.6, he goes through the analysis to determine the reactance of a discontinuity between two coupled waveguides. In that chapter, he ...
1 vote
287 views

Phase and group velocity of wave

When an electromagnetic wave enter the waveguide, what is the change in the phase and group velocity that happen in waveguide? Does wavelength or frequency of wave change when it enter the wave guide?...
165 views

Analysis of transmission lines and waveguides

While reading the transmission lines in electromagnetic field theory , I observed that while analyzing different transmission lines like co-axial cable, and two wire lines, we are using the electric ...
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Antenna CPW internal layer

I see on the internet showing CPW( coplanar waveguide) always placed on TOP layer with ground underneath. This is what I usually do. Is it possible to place a CPW in an internal layer? if so what ...
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Scattering parameters of a phase shifter

I connected a phase shifter to a VNA and measured S11 and S21. Upon setting the angle (phase) to a 100 degrees and measuring the phase of S11 I obtained the following graph, whereas theoretically S11=...
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