Novel substrate integrated waveguide filters and circuits

The main work in this thesis is to explore novel microwave filters with more compact size and improved performance by taking advantage of new substrate integrated waveguide (SIW) structures, such as the ridge substrate integrated waveguide, half mode substrate integrated waveguide (HMSIW) and SIW with complementary split ring resonators (CSRRs). This thesis therefore presents the following topics: 1. Development of a design strategy to convert from a conventional ridge waveguide configuration with solid walls to the SIW counterpart, and the design of a bandpass filter based on the ridge SIW with the proposed design method. 2. Development of a ridged HMSIW to reduce the physical size of the HMSIW by loading the HMSIW with a ridge, and application of the ridged HMSIW to the design of compact bandpass filters. 3. Development of a broadside-coupled complementary split ring resonator and a capacitively-loaded complementary single split ring resonator to reduce the size of SIW with conventional CSRRs, and application of the proposed modified structures in the design of SIW and HMSIW filters with improved compactness and performance. 4. Investigation of the application of the complementary electric-LC (CELC) resonator in SIW filters with improved stopband performance, and development of a cascaded CELC resonator to further enhance the out-of-band performance

Substrate integrated waveguide filters with face-to-face broadside-coupled complementary split ring resonators

Novel substrate integrated waveguide (SIW) filters using face-to-face oriented broadside-coupled complementary split ring resonators (BC-CSRRs) are presented in this paper. The SIW with the conventional BC-CSRR resonator pairs is first investigated. By removing the metal strip between the two back-to-back rings of the BC-CSRR pair, a modified BC-CSRR pair which shows a significantly improved spurious suppression and a wider rejection bandwidth is then proposed. SIW bandpass filters based on the resonator pairs have been designed, fabricated and measured. The SIW filter with modified BC-CSRR pairs exhibits a great improvement in the stopband performance. The proposed filters work below the cutoff frequency of the main mode of the SIW. They have the usual advantages of the SIW and the BC-CSRR such as compact size, easy fabrication and easy integration with other electronic circuits

Substrate integrated waveguide filters with broadside-coupled complementary split ring resonators

Four designs of substrate integrated waveguide (SIW) filter employing integrated broadside-coupled complementary split-ring resonators are compared. By changing the orientation of the rings, four types of SIW unit cell are proposed and investigated and it is shown that, for one particular topology, two poles and two zeros can be realised with a single unit cell. Bandpass filters based on the proposed resonators coupled by evanescent-mode SIW sections have been fabricated and tested. The proposed filters have the advantages of compact size, high selectivity and ease of integration

Wideband and UWB antennas for wireless applications. A comprehensive review

A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems

Impedance Transformers

Non

Stripline multilayer devices based on Complementary Split Ring Resonators

A new analytic design for multilayer stripline devices in planar circuit technology is presented. The Complementary Split Ring Resonator (CSRR) is used as a sub-wavelength resonant particle, which provides high-Q resonances in a compact size. The electromagnetic field distribution achieved along the stripline enables enhanced excitation of the resonators. An optimal solution for multilayer power dividers is presented, in a configuration in which each output is obtained in different layers and also in a different layer than the input line. The solution is expanded to design different devices, such as diplexers, resonators, and multi-frequency resonators, leading to vertical filters. As the resonances are achieved by stacking resonators, the effective circuit footprint is very compact. The proposed devices can be implemented in a volumetric chip fashion, allowing integration with planar transmission line circuits and flexible output connection placement. A complete analysis of the different devices is proposed, extracting and verifying their equivalent circuit models.This work was supported by Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (Agencia Estatal de Investigación, Fondo Europeo de Desarrollo Regional -FEDER-, European Union) under the research grant RTI2018-095499-B-C31 IoTrain

Reconfigurable split ring resonators using pneumatics

During the past decades, the rapid development of communication systems has extended to every aspect of modern technology. To better satisfy the need of people to interact with the world, investigations into the critical communication components mostly within the Radio-Frequency (RF) range have faced a diverse range of operational requirements and environment. The development of reconfigurable devices conforms to these demands with broader applicability. The resonant circuit, consisting of an inductance and capacitance, is fundamental to the design of passive resonant devices. The adjustment of their inherent inductance or capacitance provides a pathway for frequency reconfiguration. The split ring resonator (SRR) is first introduced to generate negative permeability in artificial materials. The physical geometry of a SRR features a gap in a broken conductive ring, and is characterised as a compact sized resonant circuit due to the effective capacitance and inductance occurring on the gap and ring respectively. The integration of SRRs to RF devices has been widely explored, not just to enhance the performance but also enable reconfiguration in some resonant devices. The concept of tuning the intrinsic capacitance or inductance of the SRR has been realised by the addition of active devices such as diodes and MEMS switches. However, interference to the electromagnetic properties due to the additional components and their bias line networks, and tolerance control on the placement of the controlling element is a serious concern. If tuning is required in array structures such as metamaterials, component count, and bias issues are significantly elevated. The aim of this research is to investigate and conceive pneumatic levitation systems as a mean of changing the structural arrangement of SRRs to reconfigure their resonant frequency or other parameters. Rotation, elevation and lateral movement of the SRRs are realised by implementing pneumatic levitation, and the resulting changes in the transmission response are characterised. The resonant frequency of a SRR is dependent on the orientation of the incident electromagnetic waves. Pneumatic levitation is firstly proposed to allow free rotation of a SRR in the azimuthal plane resulting in continuous resonant frequency variations. The inclusion of another identical SRR located below the spinning SRR forms a broad-side coupled architecture. Depending on whether the static SRR is placed parallel or perpendicular to the electric field, the coupled SRRs can achieve 10% (2.66GHz to 2.39 GHz) or 12% (2.67 GHz to 2.38 GHz) continuous frequency sweep respectively. The levitation platform which holds the SRR is demonstrated to provide different spinning speed profiles and hence frequency sweep rates for the SRR response based on various platform designs. An advanced pneumatic levitation system is devised to allow discrete on-demand resonant frequency control of broad-side coupled SRRs utilizing the rotation angle and separation of SRRs. The pneumatic structure stops the upper SRR at desired locations to achieve an associated resonant frequency response. The coupled SRRs can realise a 35% tunable frequency range (3.236 GHz to 2.11 GHz) over 180 degrees of rotation. The separation of SRRs, driven by the applied pneumatic pressure, demonstrates a tunable frequency range from 0.7% to 11.3% depending on the set rotation angle. The horizontal arrangement of SRRs introduces another dimension for structure tuning based on the lateral space between two resonators. A pneumatic levitation system which enables the manipulation of the horizontal placement of a SRR leads to a smooth conversion between edge coupled and broad-side coupled SRRs. The transition affects the mutual capacitance of the structure resulting in changes to the transmission response. A 28% frequency reduction from 3.2 GHz results during the transition from edge coupled to broad-side coupled mode if two gaps of the SRRs are initially facing each other. When the gaps are facing outwards at the start, a second resonant frequency appears in the examined band and mirrors the shift of the first resonance in the opposite direction, increasing from 3.2 GHz. The investigation of the lateral control of a SRR using pneumatic levitation is further explored with the integration of an SRR with a CPW and monopole antenna for proof of concept reconfigurable RF device functionality. The integration of pneumatic systems as an approach to tune the structure of SRRs exhibits tremendous potential for the physical modification of coupled SRRs, and possibly also any small resonant devices or components. Both simulation and experiments has demonstrated the possibilities to manipulate frequency shift between 2.1 GHz to 3.24 GHz. Furthermore its key advantages are its non-metallic structure which has minimal impact on the resonant properties and incident field, the near frictionless operation, and the control over the degrees of freedom of structural variation