Konstantinos Konstantinidis

Multilayer Partially Reflective Surfaces for Broadband Fabry-Perot Cavity Antennas

A high-gain broadband Fabry-Perot-type antenna is proposed, based on multilayer periodic partially reflective surfaces (PRSs). Three layers of PRSs are employed, consisting of metallic patches printed on thin dielectric substrates and placed in front of a ground plane, forming three open cavities. The antenna performance is based on the reflection characteristics of the PRS array, which are obtained using periodic analysis. An equivalent circuit approach is presented for the design of the multilayer PRSs showing very good agreement with full-wave analysis. The geometry has been optimized using full-wave simulations (CST Microwave Studio). An antenna of around 20-dBi gain at an operating frequency of 14.5 GHz is obtained with a 3-dB bandwidth of about 15%, outperforming earlier antenna designs based on two-layer PRS. A prototype has been fabricated and tested, validating the simulation results.

Broadband Sub-Wavelength Profile High-Gain Antennas Based on Multi-Layer Metasurfaces

A method for designing sub-wavelength-profile and broadband high-gain planar antennas is presented. A novel multi-layer periodic array design is proposed for sub-wavelength Fabry-Perot cavity type antennas with enhanced bandwidth performance. Three double-sided periodic arrays are designed and optimized, each double-sided array consisting of a capacitive artificial impedance surface (AIS) and an inductive partially reflective surface (PRS) printed on either side of a dielectric substrate. They are placed at about sixth of a wavelength from a ground plane and from each other. Thus, three air cavities are created with a total profile of λ/2. The proposed antenna has been simulated using CST Microwave Studio and measured achieving 16.9 dBi directivity with 10.7% 3 dB bandwidth. The gain-bandwidth product of the proposed designs outperforms any previous Fabry-Perot antenna design with this profile.

Dual Subwavelength Fabry–Perot Cavities for Broadband Highly Directive Antennas

A new concept for designing broadband and subwavelength profile Fabry-Perot-type antennas is introduced. A novel multilayer periodic array design is proposed, yielding two subwavelength-profile Fabry-Perot cavities that significantly enhance the bandwidth performance of the resulting highly directive antenna. The design is based on two optimized double-layer periodic arrays of dissimilar dimensions, each double-layer array consisting of a capacitive artificial magnetic conductor (AMC) layer and an inductive partially reflective surface (PRS) layer printed on either side of a dielectric substrate. They are placed at about a quarter-wavelength distance from a ground plane and from each other. Thus, two air cavities are created with a total profile of less than λ/2. The proposed antenna has been simulated in CST Microwave Studio, achieving 18.3 dBi directivity with 8% bandwidth.

Broadband near-zero index metamaterials

We present a new type of near-zero index (NZI) and epsilon near-zero (ENZ) metametarial with broad bandwidth characteristics. We propose an optimal geometry to manipulate the properties of the composite material and realize a metallic-dielectric NZI effective material operating at microwave frequencies with a broadband near-zero response. The effective material is composed by multiple layers of dissimilar metasurfaces of subwavelength dimensions. We demonstrate the broadband NZI metamaterial properties and study its anisotropy by realizing a radiating structure exhibiting broadband directive emission. An experimental demonstration validates the concept for an antenna in the microwave domain.

Design of Fabry-Perot cavity antenna at 94 GHz

A high gain planar antenna is proposed operating at W band. It is based on a Frequency Selective Surface (FSS) placed in front of a waveguide aperture in a ground plane. The FSS is printed on a thin quartz substrate which is supported on an SU8 polymer ring, forming an air cavity with the metallic ground. The geometry has been optimized using full wave simulations (CST Microwave Studio™). The antenna performance is based on the reflection characteristics of the FSS array. An antenna of around 25 dBi gain at an operating frequency of 94 GHz is obtained, suitable for imaging millimeter wave applications.

Multi-layer optimised periodic surfaces for broadband Fabry-Perot cavity antennas

Multiple-layer optimized periodic surfaces are proposed for the design of broadband Fabry-Perot high gain antennas. Three layers of periodic arrays of metallic square patche are used, printed on a dielectric substrate and placed in front of a ground plane, forming three air cavities. The geometry has been optimized using full wave simulations (CST Microwave Studio™) and a bandwidth enhancement has been achieved compared to a double layer antenna. The antenna design is based on relating the antenna performance to the reflection characteristics of the periodic array. The antenna is operating at 14 GHz with a gain of around 20 dBi and a 3dB bandwidth of around 15%.

Fabry-Perot Cavity Antennas

Fabry-Perot Cavity Antennas (FPAs) are a type of highly directive planar antennas that offer a promising alternative to standard planar microstrip patch arrays or waveguide slot array antennas. They offer significant advantages in terms of low fabrication complexity, particularly at mm wave frequencies, high radiation efficiency, and good radiation pattern performance. These advantages, in conjunction with a renewed interest in periodic surfaces and meta-surfaces, led to a reinvigoration of international research on this antenna type. This chapter reports recent advances on the design and implementation of FPAs at mm-wave bands. The main concept of FPAs, their operating principles and analysis approaches are briefly introduced. The basic types of FPAs are summarized following a historical account of various implementations until recent years. The main body of this chapter provides an overview of recent designs with a main focus on mm-wave bands and the advantages of the reported antennas for high-frequency implementations.

Low-THz Dielectric Lens Antenna With Integrated Waveguide Feed

A novel dielectric lens antenna with a broadband integrated waveguide-based feed and an optimized tapered extension is presented for low terahertz frequencies. The antenna consists of an extended hemispherical lens fed by a standard WR-3 rectangular waveguide fitted directly at the bottom of the lens. The antenna has been designed for high-resolution imaging radar systems requiring very wide bandwidth performance and highly directive beams. A novel matching technique based on an air pocket etched off the lens dielectric is employed to obtain broadband antenna operation covering the entire dominant-mode bandwidth of the waveguide. In addition, a new taper shaped lens extension is proposed for the first time and optimized to achieve improved sidelobe level and gain performance. The antenna is compatible with newly developed waveguide-based automotive radar and communications systems. The operating 3 dB gain bandwidth is 30% (230–310 GHz) achieving a maximum of 30 dB measured gain. The measured S 11 is well below –14 dB across the WR-3 band.

A THz dielectric lens antenna

In this paper, a dielectric extended hemispherical lens antenna is presented. The antenna has been designed to produce highly directive beams at low THz frequencies. The feeding mechanism is a standard WR-3 rectangular waveguide fitted at the bottom of lens. The antenna is suitable for newly developed waveguide-based automotive radar and communications systems. The initial geometry has been based on ray optics and has then been optimized using full wave simulations (CST Microwave Studio™). Various dielectric materials have been considered and rexolite (εr=2.53) has been chosen for the particular design. The antennas central frequency is 286 GHz with a maximum gain of 38.4 dBi and a 3dB bandwidth of around 40GHz.