The Water Drop Lens: Revisiting the Past to Shape the Future

This vision paper provides a brief overview on recent developments related to a new solution of quasi-optical beamformer, referred to as the water drop lens. This parallel plate waveguide beamformer, which is a revisited geodesic lens with a shaped profile, is attracting attention for applications in the millimetre-wave range, where more conventional dielectric lenses prove to be too lossy and standard geodesic lenses are still too bulky. On-going investigations include satellite and terrestrial communication systems, radar systems and imaging systems with wideband operation at centre frequencies ranging from about 20 GHz to over 120 GHz.

Amorphous WO3 thin films designed as gigahertz/terahertz dielectric lenses

Herein, tungsten oxide thin films comprising excess oxygen are treated as optical resonator suitable for gigahertz/terahertz applications. WO 3 thin films which are prepared by the thermal evaporation technique under a vacuum pressure of 10 -5 mbar are structurally, compositionally and optically evaluated. The amorphous WO 3.33 films which showed high transparency permit electronic transitions within an indirect allowed energy band gap of 3.05 eV. The band gap comprised energy band tails of width of 190 meV. Four dominant dielectric resonators centered in the infrared (IR), visible (VIS) and ultraviolet (UV) ranges of light are detected. Analysis of the optical conductivity in accordance with the Drude-Lorentz approaches have shown that the drift mobility of free holes in this amorphous layer can be as large as 5.61 cm 2 /Vs an as low as 1.59 cm 2 /Vs when exposed to IR and UV light signals, respectively. In addition, the gigahertz/terahertz cutoff frequency ( ) spectra demonstrated values in the gigahertz frequency domain when exposed to IR light. Excitations with light signals in the VIS and UV spectral ranges allow values that extends from 0.7-40.0 THz. The wide range of tunability of the WO 3 dielectric resonators nominates them as dielectric lenses suitable for optical communications.

Experimental Study of K-Band Broadband Antenna Array Using Artificial Inhomogeneous Dielectric Structures

Introduction. As a result of the extensive development of broadband communication in the millimetre wave band, there has arisen a need for antenna systems with a high level of directivity and compact dimensions, capable of operating across wide frequency ranges. However, at present, few engineering solutions satisfy this demand.Aim. To develop and study experimentally a K-band antenna array (AR) characterized by a high aperture efficiency and compact longitudinal dimensions.Materials and methods. Computer simulations were performed using the CST Studio Suite software. Measurements were carried out using an Agilent E8363B PNA vector circuit analyzer. Radiation patterns were obtained by the method of near-field scanning.Results. A K-band broadband antenna array configuration operating over the 18…26 GHz range was pro-posed. It was found that the period of the array equals 2.25 wavelengths at the highest operating frequency. In order to suppress grating lobes, an additional layer consisting of artificial inhomogeneous dielectric lenses was used. The dielectric material consisted of thin curly layers of sheet polyethylene terephthalate. Additionally, a hybrid configuration of feeding network was proposed, in which one part of the network was developed by means of printed two-wire lines, while the other part was achieved by means of rectangular waveguides. The proposed antenna array demonstrates VSWR of less than 2 and an aperture efficiency above 0.5, side and diffractive lobe levels not exceed –12 in the 18…26 GHz range. The total thickness of the configuration equals 50 mm or 4.3λmin. In order to ensure the compactness of the AR for wideband frequency applications, the thickness of the system can be reduced to 2.5λmin by excluding the waveguide part.Conclusion. When compared with existing solutions, the proposed antenna has a simpler feed network, which yields better matching. High aperture efficiency is achieved in the wide frequency range by means of inhomogeneous dielectric lenses.

Ultra-Wideband Dielectric Lens Antennas for Beamsteering Systems

This paper presents a high-directivity ultra-wideband beamsteering antenna array. An innovative beamsteering system based on hemispherical dielectric lenses fed by a set of different printed antennas is proposed. Diversity of signals in different spatial positions can be radiated at the same time. A prototype was manufactured and characterized, operating in a bandwidth varying from 8 GHz to 12 GHz with gain up to 13 dBi.