Backward Wave Microstrip Lines With Complementary Spiral Resonators

• Published in: IEEE transactions on antennas and propagation Vol. 56; no. 10; pp. 3173 - 3178
• Main Authors: Isik, O., Esselle, K.P.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.10.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied classical electromagnetism; Backward wave; Backward waves; Electromagnetic propagation; Electromagnetic wave propagation, radiowave propagation; Electromagnetism; electron and ion optics; equivalent circuit model; Exact sciences and technology; Frequency; Fundamental areas of phenomenology (including applications); Geometry; Mathematical models; Metamaterials; Microstrip components; Microstrip lines; Microstrip resonators; negative effective permeability; negative effective permittivity; Periodic structures; Permeability; Permittivity; Physics; spiral resonators; Spirals; Unit cell; Wave propagation; Microstrip lines; Electromagnetism; Prototype; metamaterials; spiral resonators; equivalent circuit model; negative effective permittivity; Wave propagation; Simulation; Spiral structure; Backward wave; Permittivity; Metamaterial; Resonators; negative effective permeability; Equivalent circuits; Periodic structures
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2008.929441

Microstrip lines loaded with series gap discontinuities and compact metamaterial particles-complementary Archimedean spiral resonators-are investigated. The theory of periodic structures is applied for establishing the propagation characteristics of infinite lines from full-wave electromagnetic simulations. Thanks to their convoluted geometry, the spirals are very compact which makes the unit cell electrically small (e.g., 0.1 guided wavelength or even smaller). Then, the effective medium theory is applied to extract the effective permittivity and permeability of the periodic structure. By analyzing the effective medium parameters and phase constant, it is shown that the structure supports backward wave propagation and exhibits double negative parameters over a 19% bandwidth around its zero-reflection frequency. Moreover, a simple equivalent-circuit model of the unit cell is established. Finally, finite-length lines with one or two complementary spirals are investigated. It is shown by comparison with full-wave results that the circuit model almost perfectly describes the structure for all practically important frequencies. It is also shown that the inter-element coupling is negligible in the multi-spiral structures considered. Measured results for two prototypes are presented to verify the analyses.