• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar
  • Skip to footer

Test & Measurement Tips

Oscilloscopes, electronics engineering industry news, how-to EE articles and electronics resources

  • Oscilloscopes
    • Analog Oscilloscope
    • Digital Oscilloscope
    • Handheld Oscilloscope
    • Mixed-signal Oscilloscope
    • PC-based Oscilloscopes – PCO
  • Design
  • Calibration
  • Meters & Testers
  • Test Equipment
  • Suppliers
  • Video
  • EE Learning Center
You are here: Home / New Articles / Basics of TEM, TE, and TM propagation

Basics of TEM, TE, and TM propagation

September 11, 2015 By David Herres 7 Comments

Energy can propagate through a medium or through what is currently believed to be a vacuum. Propagation modes vary depending upon the type of energy and the nature of the medium.

Consider sound: It can travel through any material, solid, liquid or gas. In air, sound consists of waves, discrete like a single click, or continuous, like a sustained musical tone. The waves are alternately more compressed and more rarified regions of air that radiate in concentric shells, wherever there is air. The transitions between positive and negative peaks may be smooth as in a sine wave, or abrupt as in a square wave, and there are infinite variations.

To humans, the differing waveforms are perceived as changes in sound, so we are able to recognize and differentiate between flute and saxophone, violin and French horn. Frequency variations are perceived as changes in pitch. Amplitude translates to volume. Both frequency and volume are perceived in accordance with a logarithmic scale. The volume, but not the pitch, varies with the cube of the distance.

In regard to energy conveyed through a body of water, the situation is radically different. There are two reasons. For one thing, water is far less compressible than air. The other reason is that there is a boundary condition, where water ends and air above it begins. It is here that wave action can be observed. As waves crest, the water rises above the interface, strongly opposed by gravity since water is much heavier than air. These waves become larger and the energy more visible as they approach the ocean shore, because there is less volume of water below the surface to convey all that energy.

Electromagnetic energy is also transmitted in waves. Like sound, it may propagate equally in all directions, the wave energy radiating in concentric shells corresponding to amplitude. Or it may be directional, focused to form a tight beam.

Light has a dual nature, particle or wave. It is a form of electromagnetic radiation and has associated with it electric and magnetic fields. As in other forms of electromagnetic radiation, both fields are oscillating. Depending on the transmission mode, the axis of oscillation in electromagnetic transmission may have different orientations to the direction of travel.

TEM propagationIn the Transverse Electric and Magnetic (TEM) mode, both the electric field and the magnetic field (which are always perpendicular to one another in free space) are transverse to the direction of travel. If you wonder how this is possible, bear in mind that it is happening in three-dimensional space.

TE modeTE and TM modesIn the Transverse Electric (TE) mode, the electric field is transverse to the direction of propagation while the magnetic field is normal to the direction of propagation.

In the Transverse Magnetic (TM) mode, the magnetic field is transverse to the direction of propagation while the electric field is normal to the direction of propagation.

Hollow, metallic waveguides are compatible with TE and TM modes only. This is in contrast to coaxial cable. When it is functioning as intended, the TEM mode of propagation is supported. Coaxial cable involves two conductors, the inner pin and the outer grounded shield. For this reason, capacitive losses preclude transmission at the highest frequencies. In a waveguide, including optical fiber, the outer shell or cladding functions only as a reflecting surface, so propagation takes place in one direction only, which is why there are no capacitive losses.

Filed Under: New Articles

Reader Interactions

Comments

  1. Bill Kortebein says

    October 12, 2016 at 9:14 am

    Great concise article, thanks. One comment: “normal to” means “perpendicular to.” In the following sentences, I think you meant “parallel to,” not “normal to.”

    “In the Transverse Electric (TE) mode, the electric field is transverse to the direction of propagation while the magnetic field is normal to the direction of propagation.

    In the Transverse Magnetic (TM) mode, the magnetic field is transverse to the direction of propagation while the electric field is normal to the direction of propagation.”

    Thanks again, the illustrations and article were helpful.

  2. Joseph DeLeonardis says

    April 30, 2017 at 4:34 pm

    Going off what Bill said this article should specifically say TM is parallel and TE is perpendicular to avoid confusion.

  3. Bourhan says

    April 3, 2019 at 2:52 pm

    To the guys commenting about the article, concerning the « normal to », Id likke to say that: a vector normal to another vector means that they are colinear,thus you may write A=k.B, that’s what he meant by « normal to ».

  4. Promise says

    July 18, 2019 at 8:03 am

    What are the application of the transverse Electric and Magnetic wave in communication?

  5. Carlos says

    March 30, 2020 at 1:13 pm

    Is this equivalent to what wikipedia says or wiki is wrong:
    Transverse electromagnetic (TEM) modes
    Neither electric nor magnetic field in the direction of propagation.
    Transverse electric (TE) modes
    No electric field in the direction of propagation. These are sometimes called H modes because there is only a magnetic field along the direction of propagation (H is the conventional symbol for magnetic field).
    Transverse magnetic (TM) modes
    No magnetic field in the direction of propagation. These are sometimes called E modes because there is only an electric field along the direction of propagation.
    Hybrid modes
    Non-zero electric and magnetic fields in the direction of propagation.
    https://en.wikipedia.org/wiki/Transverse_mode

  6. Asmaa says

    June 29, 2020 at 7:35 pm

    is there any reference talking about how TM mode is harder to be manipulated through waveguides?
    if there, please mention one

    thanks

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

 

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Primary Sidebar

Test & Measurement Handbook


Oscilloscopes Finder

Subscribe to our Newsletter

Subscribe to test and measurement industry news, new oscilloscope product innovations and more.

Subscribe Today

DesignFast

Component Selection Made Simple.

Try it Today
design fast globle

EE TRAINING CENTER CLASSROOMS

“ee

“ee

“ee

“ee

“ee

RSS Current EDABoard.com discussions

  • 3 Phase Sine Generation
  • Relay with ACS712 overcurrent protection (schematic included)
  • Discrete components, low distortion, variable with a single resistor, audio oscillator
  • Cadence Virtuoso Post-layout simulation using Calibre
  • Understanding two Multivibrator models

RSS Current Electro-Tech-Online.com Discussions

  • ST7066U 20x4 LCD problems
  • ZVS driver circuit
  • Dodge blower resistor modification
  • Looking for an LG 55LB6000 service manual.
  • Rant: Stupid "Smart TV" - must have video

Follow us on Twitter

Tweets by TestAndMeasure

Footer

EE World Online Network

  • DesignFast
  • EE World Online
  • EDABoard
  • Electro-Tech Online
  • Analog IC Tips
  • Microcontroller Tips
  • Power Electronic Tips
  • Sensor Tips
  • Connector Tips
  • Wire and Cable Tips
  • 5G Technology World

Test & Measurement Tips

  • Subscribe to our newsletter
  • Advertise with us
  • Contact us
  • About us
Follow us on TwitterAdd us on FacebookFollow us on YouTube Follow us on Instagram

Copyright © 2021 · WTWH Media LLC and its licensors. All rights reserved.
The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media.

Privacy Policy