Abstract
IN all smooth wave-guides and many loaded wave-guides the phase velocity has the same sign as the energy velocity. Some systems having complex forms of loading have in the past been attributed with zero or even negative group-velocities, based on apparently anomalous dispersion curves. Such phenomena have been clouded by doubts about the conception of group velocity and its relationship to energy velocity. It has recently been shown that in a periodic structure with negligible attenuation, energy and group velocities are identical1. If a system is analysed in terms of the positive solution for phase velocity, a zerogroup-velocity indicates a form of resonance with zero net power flow, and a negative group-velocity indicates a negative net energy velocity. Since in any experiment the net energy velocity is taken to be positive, systems can be devised in which the phase-velocity is negative. Dispersion curves showing guide and air wave-lengths as ordinates and abscissae must have a positive slope, and in these anomalous systems this requires a negative sign to be attributed to the measured guide wave-lengths. When interaction with charged particles is required, it is of supreme importance to determine the correct direction of the phase-velocity.
Similar content being viewed by others
Article PDF
References
Bell, J. S., A.E.R.E. Memorandum.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
MULLETT, L., LOACH, B. Wave-Guide Systems with Negative Phase Velocities. Nature 169, 1011 (1952). https://doi.org/10.1038/1691011a0
Issue Date:
DOI: https://doi.org/10.1038/1691011a0
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.