Metasurfaces: From microwaves to visible

A novel approach for the suppression of the parallel-plate waveguide (PPW) noise in high-speed printed circuit boards is presented. In this approach, one of the two conductors forming the PPW is replaced by an electromagnetic bandgap (EBG) surface. The main advantage of the proposed approach over the commonly practiced methods is the omnidirectional noise suppression it provides. For this purpose, two EBG structures are initially designed by utilizing an approximate circuit model. Subsequently, the corresponding band structures are characterized by analytical solutions using the transverse resonance method, as well as full-wave finite-element simulations. The designed EBG surfaces were fabricated and employed in a number of PPW test boards. The corresponding frequency-domain measurements exhibited bandgaps of approximately 2.21 and 3.35 GHz in the frequency range below 6 GHz. More importantly, suppression of the PPW noise by 53% was achieved based on time-domain reflectometry experiments, while maintaining the signal transmission quality within the required specifications for common signaling standards.

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Metallo-dielectric electromagnetic bandgap structures for suppression and isolation of the parallel-plate noise in high-speed circuits

Metasurfaces constitute a class of thin metamaterials, which are used from microwave to optical frequencies to create new antennas and microwave devices. Here, we propose the use of variable-impedance metasurfaces for transforming surface or guided waves into different wavefield configurations with desirable properties. We will shortly refer to this metasurface-driven wavefield transformation as “metasurfing.” Metasurfing can be obtained by an appropriate synthesis of inhomogeneous metasurface reactance that allows a local modification of the dispersion equation and, at constant operating frequency, of the local wave vector. The general effects of metasurface modulation are similar to those obtained in solid (volumetric) inhomogeneous metamaterial as predicted by the transformation optics-namely, readdressing the propagation path of an incident wave. However, significant technological simplicity is gained. Several examples are shown as a proof of concept.

Metasurfing: Addressing Waves on Impenetrable Metasurfaces

A metasurfing concept is demonstrated and applied in the design of Luneburg lens antennas. Using an array of size-varying circular patches on a dielectric substrate inside a parallel-plate waveguide (PPW) structure variable surface impedance is obtained, which realizes an equivalent refraction index as that of a Luneburg lens. The obtained lens has good bandwidth characteristics and significant fabrication advantages with respect to conventional dielectric lenses. Based on this PPW lens, an H-plane antenna has been designed and simulated.

Non-Uniform Metasurface Luneburg Lens Antenna Design

The performance of a circular microstrip patch antenna is improved using a new cylindrical electromagnetic bandgap (EBG) substrate. The microstrip patch antenna is fed by a coaxial probe and is integrated within a cylindrical electromagnetic bandgap substrate, based on the mushroom-like substrate, to increase the antenna gain. The cylindrical electromagnetic bandgap structure is a combination of two periodic structures with different periods. One is made of metallic rings and the other of grounding vias, which are disposed such as to form a radially and circularly periodic structure. A parametric analysis using a full-wave method was carried out in order to design the EBG structure. With the proposed concept, an antenna prototype was fabricated and tested. The radiation patterns and return loss obtained from measurements show a good impedance matching and a gain enhancement of the proposed antenna.

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Gain Enhancement of a Microstrip Patch Antenna Using a Cylindrical Electromagnetic Crystal Substrate

Periodic and regular metal posts, a photonic bandgap (PBG) structure for guiding surface waves in a parallel-plate waveguide is proposed. The isotropic PBG structure is applied to the design of an asymmetric parallel-plate waveguide Luneburg lens (APWLL). The relation between the dimensions of the metal posts and the required refraction index in the lens is derived with transmission-line theory and the transverse resonance method. Different lattices for the entire lens are also investigated. For verification, an antenna for a 76.5 GHz adaptive-cruise control radar is fabricated, consisting of an APWLL, a primary feed, and symmetric corrugated flares to improve the property of the antenna in elevation. Measured results verify the PBG structure design in the APWLL.

A photonic bandgap (PBG) structure for guiding and suppressing surface waves in millimeter-wave antennas

An asymmetric parallel-plate waveguide Luneburg (1964) lens (APWLL) is developed using a periodic regular circular metal post structure, which acts as a metallic artificial dielectric. The effect of metal post shapes and lattices on the angularly independent performance of the structure is investigated and then for the best angular independency a circular metal post shape and a hexagonal lattice are chosen. A prototype APWLL is designed for an adaptive cruise control (ACC) radar at 76-77 GHz. Measurement and simulation show that the structure with a hexagonal lattice and circular metal posts has not only better performance, but also functions as well as an actual isotropic homogeneous dielectric with angular independency.

Angular independency of a parallel-plate Luneburg lens with hexagonal lattice and circular metal posts

Using a single offset cylindrical parabolic reflector and an improved parallel-plate Luneburg lens, a novel antenna is developed for automotive radar in the mm-wave range. By adding linearly- or circularly-corrugated extensions to the parallel-plate Luneburg lens, a cylindrical wave illuminates the reflector, and hence good performances are achieved. Using GO, the aperture field of the antenna is found and then far-fields of the entire antenna are derived using the aperture field integration method. Design procedures of the entire antenna are presented. For verification of design rules and simulation, a prototype antenna for an adaptive cruise control (ACC) radar at 76.5 GHz is designed and measured. The antenna has properties of a relatively wide scan angle and multiple beams.

Offset cylindrical reflector antenna fed by a parallel-plate Luneburg lens for automotive radar applications in mm-wave

A new system concept for Automatic Cruise Control (ACC) is introduced which is able of covering a wide field-of-view and offers the ability of high azimuth resolution for the detection of several object within one range cell. The system makes use of digital beamforming on-receive-only to simplify the hardware requirements and to facilitate the use of high efficiency processing techniques.

Young-Jin Park

Papers

A photonic bandgap (PBG) structure for guiding and suppressing surface waves in millimeter-wave antennas

Angular independency of a parallel-plate Luneburg lens with hexagonal lattice and circular metal posts

Offset cylindrical reflector antenna fed by a parallel-plate Luneburg lens for automotive radar applications in mm-wave

A Parallel-Plate Luneburg Lens Sensor Concept for Automatic Cruise Control Applications