Radianting elements for 5G Backhauling Systems

Abstract

5G will have to support a multitude of new applications with a wide variety of requirements, including higher peak and user data rates, reduced latency, enhanced indoor coverage, increased number of devices, and so on. These aspects will lead to a radical change in network architecture from different points of view. For example, the densification of small cells produces massive backhaul traffic in the core network, which inevitably becomes an important, but somewhat less addressed bottleneck in the system. In particular, millimeter waves (mm-waves) bands, due to their large unlicensed and lightly licensed bandwidths, have become a promising candidate for the next-generation wireless communications, to accommodate users demand for multi-Gbps data rates, but this will move the attention to the complexity, the criticality and the infrastructure costs of backhauling antennas. In fact, because of the losses produced by the increasing frequency, it will be necessary to use antennas with reconfigurable directional links and, where necessary, to enable the use of massive MIMO architectures. Among the spectrum portions, the E-band and W-band are the most interesting and attractive. In fact, the unlicensed frequencies in many geographic areas will allow to reduce the operators' costs at the same bit rate. Furthermore, the directive beam steering antennas will allow the capability of spectrum reuse in the same cell. However, there are different unresolved problems, due to the need to use antennas with electronic reconfigurable beam steering both in azimuth and elevation. The spread of this kind of radiator, on a large scale, will require, necessarily, the development of new antennas that will be able to reduce manufacturing and integration costs. The main object of this work is to investigate and develop different types of new antennas, which will be able to satisfy all backhauling systems requirements for 5G applications. The research activities presented in this dissertation can be summarized into three parts. In the first part, a beam-switched Cassegrain reflector antenna in E-band (71-86 GHz) for backhauling systems for 5G applications is presented, including the study of different feeding elements which will illuminate the double reflector system. This antenna has been thought to reconfigure the beam compensating small boom movements, which are estimated to be within ±1° in both azimuth and elevation planes. After evaluating all the possible solutions, an array of magneto-electric dipoles has been selected as feeding element for the E-band beam-switched Cassegrain antenna. In the second part, the attention has been focused on the study and the design of antennas on-chip (AoCs) in a standard 0.13 μm SiGe BiCMOS technology. In particular, two new techniques for enhancing the gain of on-chip monopole antennas in W-Band (75-110 GHz) are proposed. These new proposed methodologies involved the use of a new AMC (Artificial magnetic conductor), composed by some SRRs (Split ring resonators) and LBE (Localized Backside Etching), and some capacitively loaded SRRs. In the last part, a I/Q phase shifter design in E-band (71-86 GHz) in a SiGe BiCMOS 55 nm semiconductor technology is proposed. The proposed phase shifter is a sub-block of a compact E-band I/Q Receiver in SiGe BiCMOS for 5G backhauling applications.