Mode (electromagnetism)

The mode of electromagnetic systems describes the field pattern of the propagating waves.^[1]: 369

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.^[2]: A.4
  • Transverse modes, modes that have at least one of the electric field and magnetic field entirely in a transverse direction.^[3]: 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.^[4]: 550
    • HE modes, hybrid modes in which the TE component dominates.
    • EH modes, hybrid modes in which the TM component dominates.
    • Longitudinal-section modes^[5]: 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^[2]: 5.4.3 and as the eigenfunctions in a eigenmode expansion analysis of waveguides.^[6]
    • Similarly natural modes arise in the singular expansion method of waveguide analysis and characteristic modes arise in characteristic mode analysis.^[6]
• Modes in other structures
  • Bloch modes, modes of Bloch waves; these occur in periodically repeating structures.^[7]: 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.^[8]: 123

References

1. Jackson, John David (1975). Classical electrodynamics (2d ed.). New York: Wiley. ISBN 978-0-471-43132-9.
2. Rothwell, Edward J.; Cloud, Michael J. (2001). Electromagnetics. Electrical engineering textbook series. Boca Raton, Fla: CRC Press. ISBN 978-0-8493-1397-4.
3. Connor, F. R. (1972). Wave transmission. His Introductory topics in electronics and telecommunication. London: Edward Arnold. ISBN 978-0-7131-3278-6.
4. Chen, Wai Kai (2004). The Electrical Engineering Handbook. Elsevier. ISBN 0-0804-7748-8.
5. Zhang, Kequian; Li, Dejie (2008). Electromagnetic Theory for Microwaves and Optoelectronics. Berlin, Heidelberg: Springer Berlin Heidelberg. doi:10.1007/978-3-540-74296-8. ISBN 978-3-540-74295-1.
6. Huang, Shaode; Pan, Jin; Luo, Yuyue (2018). "Study on the Relationships between Eigenmodes, Natural Modes, and Characteristic Modes of Perfectly Electric Conducting Bodies". International Journal of Antennas and Propagation. 2018: 1–13. doi:10.1155/2018/8735635. hdl:10453/132538. ISSN 1687-5869.
7. Yang, Jianke (2010). Nonlinear waves in integrable and nonintegrable systems. Mathematical modeling and computation. Philadelphia: Society for Industrial and Applied Mathematics. ISBN 978-0-89871-705-1.
8. Edwards, T. C.; Steer, Michael Bernard (2016). Foundations for microstrip circuit design (Fourth ed.). Chichester, West Sussex, United Kingdom: IEEE Press, Wiley. ISBN 978-1-118-93619-1.