Mode (electromagnetism)
The mode of electromagnetic systems describes the field pattern of the propagating waves.{{Cite book |last=Jackson |first=John David |title=Classical electrodynamics |date=1975 |publisher=Wiley |isbn=978-0-471-43132-9 |edition=2d |location=New York}}{{rp|369|q=...the electromagnetic fields in a hollow guide are described by an infinite set of characteristic or normal modes...}}
Some of the classifications of electromagnetic modes include;
- Modes in waveguides and transmission lines. These modes are analogous to the normal modes of vibration in mechanical systems.{{rp|loc=A.4|q=Physically, the wave function ψ represents the so-called eigenvalue or normal mode solutions for the “TM modes” of a rectangular cavity.}}
- Transverse modes, modes that have at least one of the electric field and magnetic field entirely in a transverse direction.{{rp|52}}
- 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 of the corresponding TE and TM modes.{{rp|550}}
- HE modes, hybrid modes in which the TE component dominates.
- EH modes, hybrid modes in which the TM component dominates.
- Longitudinal-section modes{{rp|294}}
- 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
- The term eigenmode is used both as a synonym for mode{{Cite book |last1=Rothwell |first1=Edward J. |title=Electromagnetics |last2=Cloud |first2=Michael J. |date=2001 |publisher=CRC Press |isbn=978-0-8493-1397-4 |series=Electrical engineering textbook series |location=Boca Raton, Fla}}{{rp|loc=5.4.3|q=...the transverse behavior of the waveguide fields. When coupled with an appropriate boundary condition, this homogeneous equation has an infinite spectrum of discrete solutions called eigenmodes or simply modes.}} and as the eigenfunctions in a eigenmode expansion analysis of waveguides.{{Cite journal |last1=Huang |first1=Shaode |last2=Pan |first2=Jin |last3=Luo |first3=Yuyue |date=2018 |title=Study on the Relationships between Eigenmodes, Natural Modes, and Characteristic Modes of Perfectly Electric Conducting Bodies |journal=International Journal of Antennas and Propagation |language=en |volume=2018 |pages=1–13 |doi=10.1155/2018/8735635 |doi-access=free |issn=1687-5869|hdl=10453/132538 |hdl-access=free }}
- Similarly natural modes arise in the singular expansion method of waveguide analysis and characteristic modes arise in characteristic mode analysis.
- Modes in other structures
- Bloch modes, modes of Bloch waves; these occur in periodically repeating structures.{{rp|291}}
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.{{rp|123}}