The mode of
electromagnetic radiation
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic field, electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, inf ...
describes the field pattern of the propagating waves. Electromagnetic modes are analogous to the
normal mode
A normal mode of a dynamical system is a pattern of motion in which all parts of the system move sinusoidally with the same frequency and with a fixed phase relation. The free motion described by the normal modes takes place at fixed frequencies. ...
s of vibration in other systems, such as mechanical systems.
Some of the classifications of electromagnetic modes include;
* Free space modes
**
Plane wave
In physics, a plane wave is a special case of wave or field: a physical quantity whose value, at any moment, is constant through any plane that is perpendicular to a fixed direction in space.
For any position \vec x in space and any time t, th ...
s, waves in which the electric and magnetic fields are both orthogonal to the direction of travel of the wave. These are the waves that exist in free space far from any antenna.
* Modes in waveguides and transmission lines
**
Transverse mode
A transverse mode of electromagnetic radiation is a particular electromagnetic field pattern of the radiation in the plane perpendicular (i.e., transverse) to the radiation's propagation direction. Transverse modes occur in radio waves and microwav ...
s, modes that have at least one of the electric field and magnetic field entirely in a transverse direction.
*** Transverse electromagnetic mode (TEM), as with a free space plane wave, both the electric field and magnetic field are entirely transverse.
*** Transverse electric (TE) modes, only the electric field is entirely transverse. Also notated as H modes to indicate there is a longitudinal magnetic component.
*** Transverse magnetic (TM) modes, only the magnetic field is entirely transverse. Also notated as E modes to indicate there is a longitudinal electric component.
** Hybrid electromagnetic (HEM) modes, both the electric and magnetic fields have a component in the longitudinal direction. They can be analysed as a
linear superposition
The superposition principle, also known as superposition property, states that, for all linear systems, the net response caused by two or more stimuli is the sum of the responses that would have been caused by each stimulus individually. So tha ...
of the corresponding TE and TM modes.
*** HE modes, hybrid modes in which the TE component dominates.
*** EH modes, hybrid modes in which the TM component dominates.
***
Longitudinal-section mode Longitudinal-section modes are a set of a particular kind of electromagnetic transmission modes found in some types of transmission line. They are a subset of hybrid electromagnetic modes (HEM modes). HEM modes are those modes that have both an e ...
s
**** Longitudinal-section electric (LSE) modes, hybrid modes in which the electric field in one of the transverse directions is zero
**** Longitudinal-section magnetic (LSM) modes, hybrid modes in which the magnetic field in one of the transverse directions is zero
* Modes in other structures
** Bloch modes, modes of
Bloch wave
In condensed matter physics, Bloch's theorem states that solutions to the Schrödinger equation in a periodic potential take the form of a plane wave modulated by a periodic function. The theorem is named after the physicist Felix Bloch, who di ...
s; these occur in periodically repeating structures.
Mode names are sometimes prefixed with ''quasi-'', meaning that the mode is not quite pure. For instance, quasi-TEM mode has a small component of longitudinal field.
[Edwards & Steer, pp. 123-124]
References
Bibliography
* Connor, F R, ''Wave Transmission'', Edward Arnold, 1972 .
* Chen, Wai Kai, ''The Electrical Engineering Handbook'', Elsevier, 2004 .
* Edwards, Terry; Steer, Michael, ''Foundations for Microstrip Circuit Design'', Wiley, 2016 .
* Yang, Jianke, ''Nonlinear Waves in Integrable and Non-integrable Systems'', Society for Industrial and Applied Mathematics, 2010 .
* Zhang, Kequian; Li, Dejie, ''Electromagnetic Theory for Microwaves and Optoelectronics'', Springer, 2013 {{ISBN, 3-662-03553-7.
Wave mechanics
Electromagnetic radiation
Microwave transmission