S‐parameter measurements for oblique angles of incidence and Brewster angle studies for metamaterial samples

To date, most numerical and experimental studies of metamaterials are limited to normally incident plane waves with the magnetic field parallel to the axis of the inductive structure. In this article, the reflected field response of three types of Split Ring Resonator (SRR) media are measured as a function of incident field polarization, angle of incidence and frequency, using an automated free space focused beam measurement system. The measured results are compared with simulated data generated using the experimentally retrieved complex permittivity and permeability tensors from normal incidence measurements. It is concluded that there is no classical Brewster angle (zero reflection for a given angle of incidence). However, we observe a reflection minimum for all angles of incidence in a small range of frequencies close to the plasmon frequency for all orientations of the SRRs for perpendicular polarization. This will indeed have important low observable applications. In parallel polarization, SRR media are transparent for small angles of incidence. For both polarizations, the effect of anisotropy becomes significant as the angle of incidence increases and a significant change in the reflected field is observed. Thus, considering the anisotropic nature of such metamaterials is important when designing applications. In this article, we also independently verify the assumed constitutive models and property retrieval using normal incidence measurements, using oblique incidence scans. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2619–2624, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21986