7. G. Tayeb and D. Maystre, Rigorous theoretical study of finite-size two-dimensional photonic crystals doped by microcavities, J Opt Soc Am A 14 (1997), 3323–3332. 8. M. Bertero and P. Boccacci, Introduction to inverse problems in imag- ing, The Institute of Physics Publishing, Bristol, UK, 1998. 9. J. Yonekura, M. Ikeda, and T. Baba, Analysis of finite 2-d photonic crystals of columns and lightwave devices using the scattering matrix method, J Lightwave Technol 17 (1999), 1500 –1508. © 2006 Wiley Periodicals, Inc. MEMS-BASED HIGH-IMPEDANCE SURFACES FOR MILLIMETER AND SUBMILLIMETER WAVE APPLICATIONS Dmitry Chicherin, 1 Sergey Dudorov, 1 Dmitri Lioubtchenko, 1 Victor Ovchinnikov, 2 Sergei Tretyakov, 1 and Antti V. Ra ¨ isa ¨ nen 1 1 Radio Laboratory/SMARAD Helsinki University of Technology P.O. Box 3000 FI-02015 TKK, Finland 2 Microelectronics Centre Helsinki University of Technology P.O. Box 3500 FI-02015 TKK, Finland Received 8 June 2006 ABSTRACT: The authors propose to use microelectromechanical sys- tems (MEMS) to produce novel phase shifters based on an electronically reconfigurable high-impedance surface (HIS). Typically, HIS is a tex- tured metal surface with reactive impedance varying from an initial value to a very high value. Such phase shifters can be developed with introducing a surface with variable impedance in, e.g., a rectangular metal or dielectric rod waveguide. Placed along narrow walls of the rectangular metal waveguide or adjacent to the dielectric waveguide, the HIS affects the propagation constant, which results in changing the phase of the propagating wave. The authors manufactured a prototype of the microelectromechanical systems-based HIS consisting of a dielec- tric layer placed on a ground plane, and two arrays of metal patches. The gap between the upper and lower arrays of patches was fixed and filled with SiO 2 . The measured phase of the wave reflected from the pro- totype HIS varies in the range of 50°, and its insertion loss is below 0.5 dB (out of resonance). © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2570 –2573, 2006; Published online in Wiley Inter- Science (www.interscience.wiley.com). DOI 10.1002/mop.21997 Key words: MEMS; high-impedance surface; millimeter wave phase shifter 1. INTRODUCTION The millimeter and submillimeter wavelength region is of in- creasing interest for many applications beyond the traditional radio astronomy and atmospheric remote sensing, namely, se- cure high-capacity communication systems, spectroscopy, med- ical diagnostics, radar, etc. Despite a higher price of basic components, e.g., phase shifters, in comparison with those at microwaves, millimeter wave systems meet expanding interests of customers. There are two categories of existing millimeter wave phase shifters. In the first category, the phase is changed by adjusting the geometrical parameters of the device, e.g., changing the length of a transmission line using semiconductor switches. Because of the relatively large size, these phase shifters are not convenient in phased arrays. In the second category of phase shifters, the material properties of its com- ponents (e.g., ferroelectrics or ferrites) are altered by applying magnetic or electric field. Such phase shifters usually are very lossy at millimeter wavelengths. Therefore, metamaterials [1], i.e., structures that can be engineered to respond to electromag- netic fields in unconventional ways, and artificial surfaces can be a solution. microelectromechanical systems (MEMS) [2] offer many advantages in manufacturing of metamaterials. MEMS are miniature structures combining electrical and me- chanical properties and fabricated by micromachining tech- niques. MEMS-based devices provide good functional param- eters, e.g., low losses and reconfigurability, owing to a small size and a high process precision. We have proposed [3] to use high-impedance surfaces (HIS) based on MEMS so as to produce novel millimeter and submil- limeter wave phase shifters. Typically, HIS is a corrugated metal surface which impedance can achieve extremely high values at some frequency range. As a result, the reflection coefficient of the HIS is equal to 1 208 0° instead of 1 208 180° as for metal surfaces. Conventional HIS [4] consists of a two-dimensional capacitive array of metal patches placed on a grounded dielectric layer. If the period of the array of patches is much smaller than the wavelength of the field incident on the HIS or propagating above it, an effective surface impedance model [1] can be used to characterize the electromagnetic Figure 1 Frequency dependence of the HIS reflection phase, simulated Figure 2 MEMS-based reconfigurable HIS 2570 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 48, No. 12, December 2006 DOI 10.1002/mop