Design and implementation of metamaterial - inspired transmissive and radiating microwave components

Abstract

In this thesis, we present the design and the implementation of several metamaterial-inspired transmissive and radiating microwave components, which can be easily integrated in practically realizable systems. First, we analyze the use of non-Foster active circuits to obtain a widening of the operating bandwidth of devices based on metamaterials (MTMs). In particular, the more suitable loading circuit is analytically determined and it is used to dramatically increase the operating bandwidth of an electrically small antenna consisting of a monopole loaded with a single split-ring resonator (SRR). The non-Foster circuit is designed by using only real components and the stability of the entire system is properly evaluated. Then, we present some radiating elements based on the use of MTM-inspired resonant inclusions. As a first example, we propose a multi-functional antenna consisting of a printed monopole and two SRRs. Next, we design a compact antenna for Wi-Fi application consisting of two orthogonal parasitic meandered monopoles and a driven bow-tie. Third, we propose a new class of horn antennas with integrated MTM-inspired filtering modules. In particular, we present some horn antennas that, depending on the used resonant inclusion, show a band-pass or band-stop filtering behavior. Afterward, we focus our attention on non-radiative elements. In particular, by using complementary electrically small resonators, we design some compact microwave components (i.e. waveguide transition, power dividers, orthomode transducer) that, at the same time, show also a band-pass filtering behavior. Moreover, we design a novel and low-cost MTM-inspired absorber operating in X-band. Finally, we explore the possibility to generate an electromagnetic field with a non-zero orbital angular momentum (OAM) using a single patch antenna. In particular, we report an analytical study of a circular patch antenna in order to show that a circular polarized TMnm mode generates an OAM of order n-1. Then, we design an elliptical patch antenna that radiates a circular polarized electromagnetic field with OAM of the first order.