Advanced Technologies for SIW Passive Microwave Components

The rapid growth of wireless networks and technologies of the last few decades has imposed new requirements on the performance of microwave components. There is a demand for wireless devices and sensors with high performance, high miniaturization and low production cost. Given this framework, the aim of this work is to provide a useful contribution through the study of existing techniques and the proposal of new ones. This is done by pursuing two specific lines of research: the study and analysis of compact Substrate Integrated Waveguide (SIW) resonators and filters, and the development of particularly simple and inexpensive reconfigurable antenna arrays based on an innovative amplitude beam-steering technique. Resonators are used as the basis for many different microwave devices. The achievable performance of said devices is limited by the losses of their resonators. The SIW is a planar transmission line technology which is a promising candidate for a wide array of applications. Compared to other planar technologies, the SIW offers particularly low losses and high electromagnetic performance, with an increase in the size of the components as a trade-off. In order to increase the miniaturization of SIW devices, the Half-Mode technique has been proposed, resulting in the Half-Mode Substrate Integrated Waveguide (HMSIW) topology. The Half-Mode technique can be applied multiple times to the classic square SIW resonator. With every iteration, the miniaturization factor is increased. The topologies that can be obtained are the Half-Mode resonator, the Quarter-Mode resonator and the Eighth-Mode resonator. While the SIW topology is completely closed and electromagnetically shielded, HMSIW and derived structures are partly open. For this reason, the performance of HMSIW devices suffer from the introduction of leakage and radiation losses. This work offers a study on the performance of the size reduction technique by the systematic analysis of these topologies. In a practical application, the results of this analysis are used to find which compact topology may be more convenient to employ depending on the design constraints such as frequency or kind of substrate to use. In order to mitigate the problem of losses, a few modified topologies which offer a substantial increase in the Quality Factor for only a modest increase in the size of the resonators have been proposed. An antenna array is defined as a group of antenna elements which operate concurrently. By acting on the relative phase of the signal of each radiator, it is possible to control the shape and orientation of the radiation pattern of the entire array. A phased array provides a high level of flexibility on the shape of the radiation pattern, but it is usually a complex system which requires a high amount of control elements. This work proposes an alternative technique that can be used to synthesise arrays with beam-steering properties without the use of phase shifters. The array is divided in two sub-arrays with the same amount of elements. Each sub-array is designed with a fixed phase profile and direction of maximum radiation. The pointing direction of the overall radiation beam can be controlled by adjusting the ratio of signal power being distributed between the two sub-arrays. The proposed technique manages to minimize the amount of control elements required to obtain beam-steering, since only a single power divider is needed. Fixed sub-array cells are simple to design and implement. The result is a large reduction in the complexity of the system. This work presents in detail the advantages, limits and drawbacks of the proposed amplitude-based beam steering technique. This technique is then used to design two different antenna arrays for 5G applications.