Flat mirror for millimeter-wave and terahertz imaging systems using an inexpensive metasurface

Abstract

Flat mirrors, also known as flat parabolic surfaces, for millimeter-wave and terahertz imaging systems are demonstrated. This flat mirror is based on the metasurface in which an inexpensive printed circuit board technology is used to realize copper patterns printed on an FR4 substrate. Compared to the conventional reflector antennas used today in diverse applications (for homeland security, medical systems, communication, etc.), the suggested mirror has major advantages in process simplicity, mechanical flexibility, frequency alignment, weight, and cost. The theoretical background, simulation results, experimental results, and proof of concept are given in this Letter. OCIS codes: 110.6795, 160.3918, 230.4040, 240.6700. doi: 10.3788/COL201715.011101.In recent years, the use of millimeter-wave (MMW) applications (for homeland security, communication, medicine, etc.) has grown significantly, especially in the case of applications based on imaging systems [1] . The lack of quasioptical components for the 30-300 GHz frequency range, such as large-aperture mirrors and inexpensive detectors and sources, is noticeable. The high cost, complicated production processes, and alignment difficulties call for the development of low-cost MMW components for quasi-optical and imaging systems [2] . A good example of such a component is the glow discharge detector, which is a very inexpensive detector for MMW imaging systems that costs about $0.30 [3][4][5] . On the other hand, the imaging mirror is very expensive and very difficult to align due to its weight and large aperture. Mirrors with large apertures equal to 500 mm and greater are required for proper MMW image quality and maintenance of the focal point generally close to its diffraction limit [6] . In this Letter, we will present an alternative imaging mirror design based on a planar surface for MMW imaging, which is very inexpensive and lightweight and is known as a flat parabolic surface (FLAPS) [7] . This FLAPS design is based on an array of variabledimension metal cells (a metasurface), which are connected to the ground plane through a dielectric substrate. This unique structure is a particular case of two-dimensional (2D) metamaterial called a metasurface [8] . The dielectric constants of the substrate and size of each metal cell determine its electrical characteristics, such as capacitance and inductance, as well as its electromagnetic properties [9] . MMW radiation incident to the FLAPS mirror surface causes currents to flow from the top surface of the dipoles to the ground plane through a passive array of capacitors and inductors, which cause a phase shift in the reflected electromagnetic wave (see Fig. 1). By varying the size of a dipole, we basically vary its phase shift, depending on its location on the FLAPS mirror surface (see Fig. 1). In this study, the metasurface mirror structure was composed of an FR4 (glass epoxy) dielectric substrate with a ground plane in the back and printed metal patterns on the front. Each metal cell on the front is connected to the...

Realization and validation of continuous tunable metasurface for high resolution beam steering reflector at K‐band frequency

“…MS is used in various frequencies for different electrical engineering fields 1 . For example, compact filters 2,3 and special antennas 4 in sub 6 GHz, reflecting focusing in K‐band, 5 flat parabolic surface for imaging, and beam propagation manipulation in W‐band 6 . MS perfect absorber was designed to detect micro‐poisons in drinking water in millimeter‐wave 7 .…”

Innovative Reconfigurable Metasurface 2-D Beam-Steerable Reflector for 5G Wireless Communication

“…Due to a planned gradual phase provided by the unit cells MS reflector, the rays are reflected at the desired angle θ. The optical path difference (OPD) between the cells is defined as ∆L [9] and is shown in Equation 4∆L…”

“…There are many interdisciplinary applications where MSs play an important role [7]. For example, a millimeter-wave MS perfect absorber was designed to detect micro-poisons in drinking water [8], and a flat parabolic surface was used in W-band imaging and beam propagation [9]. These MSs are based on resonant unit cells and are limited to a narrow bandwidth around a fixed working frequency.…”

Wideband reconfigurable entire Ku‐band metasurface beam‐steerable reflector for satellite communications

“…Due to a planned gradual phase provided by reconfigurable MS, the rays are reflected at an angle θ. The optical path difference (OPD) between the cells is defined as ΔL and is described [3] ΔL = ΔX ⋅ sin θ…”