Departmental Papers (ESE)


In this Letter, we address the issue of Foster's reactance theorem for the material media in which one or both of the material parameters ε and μ may possess negative real parts. We demonstrate that this theorem is indeed satisfied for a one-port termination filled with a lossless metamaterial with negative real permittivity and permeability, known as a "double-negative (DNG)" medium, or with a lossless metamaterial with either negative real permittivity or negative real permeability, which can be named as a "single-negative (SNG)" medium. However, in the case of DNG media when the reactive input impedance of such a termination is compared with that of its counterpart filled with a conventional lossless "double-positive (DPS)" material, it is found that the two reactances have opposite signs. Similar conclusions can be made for a termination filled with a lossless epsilon-negative (ENG) material when it is compared with that of its mu-negative (MNG) counterpart. Therefore, if a one-port termination filled with a lossless DPS or ENG material possesses inductive input reactance, when the same termination is filled instead with a lossless DNG or MNG material, its input reactance may be capacitive.

Document Type

Journal Article

Date of this Version

October 2003


Postprint version. Published in Microwave and Optical Technology Letters, Volume 39, Issue 1, October 5 2003, pages 11-14.
Publisher URL:

A portion of this work was presented and appeared in the CD of the XXVII General Assembly of International Union of Radio Science (URSI GA’02), Maastricht, The Netherlands, August 17-24, 2002.


composite materials, negative permittivity, metamaterials



Date Posted: 24 July 2007

This document has been peer reviewed.