Wide-Angle Beam Scanning Transmit-array Fed Using Ridge-gap Waveguide DRA for 60 GHz Wireless Communications

This paper introduces a planar Transmit-array illuminated by a compact dielectric resonator antenna (DRA) for 60 GHz communications. The unit-cell is a compact square patch surrounded by square split-ring printed back-to-back to dielectric substrate with drilled cylindrical holes. The unit-cell dimensions are tuned for 60 GHz transmission phase range variation of 360^o with a transmission magnitude of −4 dB. The phase is controlled via changing the patch length. 13×13 unit-cells Transmit-array are designed for broadside radiation with high gain. The feeding element is square DRA excited by slot-coupled ridge-gap waveguide (RGW) cavity for high gain and compact size. The radiation characteristics of the Transmit-array fed with RGW-DRA is compared with using a conventional horn antenna as a feeder. Wide-angle beam scanning from −50⁰ to+ 50⁰ is achieved via changing the phase destitution over the Transmit-array aperture. The peak gain is 15.17 dBi with half-power beamwidth 6.8 degrees.

I. Introduction

High-gain antennas are essential in various modern communications applications such as satellites, remote sensing, and 5G communications [1] . Transmit array antennas belong to the high gain antenna group and they combine the features of phased array and parabolic reflector but with low-profile and conformal design [2] . It consist of a feeding source element and a thin-transmitting surface of half-wavelength unit-cell elements. The feeding source is located at the equivalent focus of the transmit array. The unit-cell elements are designed with transmission coefficients adjusted to convert the spherical-waves from the feed to a plane-waves [3] . The selection of the feeding element is essential in transmit array performance. Recently, modern communication technologies are moving toward to the millimeter wave band such as 5G/6G system. The use of high frequency bands is characterized by unlicensed bands, using high directive antenna, secure transmission, and immunity to interference [4] . These communication technologies combine the analog, digital radio systems and the antenna together in the same chip at millimeter frequencies. The employment of classical technologies, such as microstrip lines and waveguides with these integrated modules is so difficult [5] . Hence, the researches have recently attracted the attention to develop new technologies with high performance, such as the ridge-gap waveguide (RGW) technology [6] . The basic theory of RGW technology is the use of artificial magnetic conductor (AMC) surface to create high impedance to guide the field only along desired paths, and stop it along other directions [7] . The RGW has three forms to guide the electromagnetic waves in the gab are ridge- gap waveguide, groove-gap waveguides and microstrip-gap waveguide [8] .