Analytical Design Procedures for the Odd Mode of Ridge Gap Waveguide Devices and Antennas

The millimeter-wave (mm-wave) band has attracted attention due to its wideband characteristics that make it able to support multi-gigabit per second data rate. Nevertheless, the performance of mm-wave wireless communication systems is restricted due to attenuation loss. Design of mm-wave components and antennas is rapidly growing with the current evolution in the wireless communication systems. However, the traditional waveguide structures such as microstrip, coplanar, substrate integrated waveguide, and rectangular waveguide either suffer from high losses or difficulty in manufacturing at mm-wave band. The ridge gap waveguide (RGW) technology is considered as a promising waveguide technology for the mm-wave band. RGW technology overcomes the conventional guiding structure problems as the wave propagates in an air gap region which eliminates the dielectric loss. Moreover, RGW does not need any electrical contacts, unlike traditional rectangular waveguides. Also, the RGW can be implemented in the printed form (PRGW) for easy integration with other planer system components. In this thesis, the use of the odd mode (TE10 (RGW)) RGW to design mm-wave components and antennas is presented. First, a systematic design methodology for the RGW using hybrid PEC/PMC waveguide approximation is presented. This reduces the design time using full wave simulators. The concept has been verified by simulation and experimental measurements. Second, two different methods to excite the odd mode in RGW are studied and investigated. In the first method, a planar L-shape RGW is used where less than -10 dB reflection coefficient is achieved, from 28 to 36 GHz, and more than 93% of the input power has been converted into the odd mode at the output port. The second method uses a magic tee with a shorted sum port and provides a wideband pure odd mode at the output port with reflection coefficient less than -10 dB from 28 GHz to 39 GHz. Other mm-wave components based on odd mode TE10 RGW are designed and presented including a Y-junction power divider and 3 dB forward coupler are designed for the first time in RGW technology. The Y-junction has a wideband matching from 28 to 34 GHz with a reflection coefficient less than -15 dB and the transmission output levels are about -3.3 dB. The usefulness of the odd mode RGW lies in the ability to increase the channel bandwidth that has been achieved by designing a dual-mode RGW. A magic tee is used to simultaneously excite the fundamental mode Q-TEM and the odd mode TE10 (RGW) on the ridgeline. The proposed dual-mode RGW performance is verified through simulation and measurement of a back-to-back configuration. The proposed design achieves a matching level less than -10 dB for the two modes over the frequency range from 29 GHz to 34.5 GHz with isolation better than 23 dB. The dual-mode RGW is then used to feed a reconfigurable Vivaldi horn antenna where two different radiation patterns can be obtained depending on the excited mode. The Q-TEM generates a single beam pattern, while the odd mode TE10 (RGW) generates a dual-beam pattern. The maximum gain for the single beam radiation is 12.1 dBi, while it is 10.43 dBi for the dual-beam pattern. The bandwidth of the dual-mode antenna is 25% at 32 GHz with impedance matching less than -10 dB and isolation better than 20 dB. Finally, several antennas are presented in this thesis based on the odd mode RGW. A novel differential feeding cavity antenna using the odd mode of RGW is presented. The measured results show good performance in terms of gain, bandwidth, sidelobe level, and cross-polarization. The maximum gain is 16.5 dBi, and the sidelobe level is -17 dB and -13.8 dB, for the E-plane and H-plane, respectively. Moreover, the proposed antenna has low cross-polarization levels of -35 dB in the E-plane and -27 dB in the H-plane. In addition, two 2x1 linear frequency scanning array antennas are designed and implemented using the proposed Y-junction to generate single beam and dual-beam patterns. The beam scan is from -11(degree) to -40(degree) at 28 GHz and 32 GHz, respectively

Millimeter-wave Substrate Integrated Printed Ridge Gap Waveguide Leaky-Wave Antenna for WiGig Applications

Abstract Millimeter-wave Substrate Integrated Printed Ridge Gap Waveguide Leaky-Wave Antenna for WiGig Applications Mohammad Reza Rahimi, MASc. Concordia University, 2018 Leaky-wave antennas have been an interesting topic for researchers for more than half a century. As millimeter-wave frequencies applications are in high demand for communication companies due their wider bandwidth, designing a leaky-wave antenna, for this frequency range is becoming more challenging with the demand for low-loss and low-cost components. Since high-performance hollow waveguides, as a low loss guiding structure, drives the cost to an unacceptable level and microstrip technology, as a low-cost transition, has an unacceptably high loss. Therefore, the requirements for a new technology that achieves both low cost and high performance feels more tangible. The new technology of substrate integrated printed ridge gap waveguide that was proposed in 2016 shows promising characteristics as a new modified gap waveguide structure for millimeter-wave applications in terms of low insertion loss and low cost. Therefore, it is necessary to propose a new desirable class of microwave components based on this technology. Here, we propose the use of this technology to design three leaky-wave antennas. The work of this thesis is divided into three major parts: (1) designing a periodic structure which has a leaky mode for a specific range of frequencies, and (2) designing a 1D-periodic leaky-wave antenna based on a periodic structure and connecting the antenna to the standard 50 Ω equipment. For achieving this purpose a quasi-TEM transition and a transition from microstrip to substrate integrated ridge gap waveguide has been designed. In addition, the slots of the proposed antenna are designed in order to have an almost constant leakage ratio through the whole operating frequency band. (3) The third part will discuss a linear array of the proposed antenna in which a new termination has been considered which results in a shorter physical length. The proposed antennas can be easily fabricated with a low-cost multi-layered PCB technology. In addition, all these antennas designed for the WiGig applications which are more attractive for today's requirements. Keywords: Leaky-wave antenna; gap waveguide; electromagnetic band ga

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

New Integrated Waveguides Concept and Development of Substrate Integrated Antennas with Controlled Boundary Conditions

The unprecedented development of substrate integrated circuits (SICs) has made a widespread necessity for further studies and development of waveguides and antennas based on this technology. As the operating frequency is on the rise, the conventional designs of the substrate integrated components are becoming more problematic and costly. Therefore, some techniques are proposed to improve the performance of the waveguides and antennas based on the concept of substrate integrated technology. First, the problems of the recently developed ridge gap waveguide (RGW) are resolved by introducing a new configuration of this technology which has considerable advantages over the original version of the RGW regarding its construction technology, propagation mode, characteristic impedance, and insertion loss. Second, the configuration of substrate integrated waveguide (SIW), which has been widely accepted for planar and integrated microwave circuits, is modified to operate with low insertion loss at high frequencies without bearing the anisotropic nature of the dielectric material. The substrate integrated antennas have a strong potential to be used in the compact wireless devices as they can be easily integrated with the baseband circuits. In the horn family, the H-plane horn antenna that can be implemented in the integrated form has received considerable attention in recent years. However, numerous problems are associated with this antenna such as limited bandwidth, tapered aperture distribution, high back radiation, and E-plane asymmetry. Several new techniques are introduced to improve the performance of this antenna, especially at millimeter wave frequencies

Étude et réalisation de matrices à commutation de faisceaux en technologie guide d'ondes intégré au substrat

RÉSUMÉ Les applications radar pour les voitures demandent des composants de hautes performances mais avec faible coût de revient. Cette thèse présente la conception des réseaux d’alimentation d’antennes en ondes millimétriques utilisant la technologie du guide d’ondes intégré aux substrats (GIS), pour satisfaire les exigences du coût et du faible encombrement dans ces applications de radar. Dans un système radar, l’antenne défini la largeur du secteur couvert, la portée, la discrimination angulaire et le filtrage du bruit généré par d’autre sources. Généralement les antennes intelligentes remplissent ce cahier des charges. La direction dans laquelle le réseau ayant la réponse maximale serait la direction du pointage de faisceau. Pour un choix de faisceau dans une direction désirée, un ajustement de phase doit être accompli. Les matrices à commutation donnent des distributions de phase aux sorties différentes pour chaque port d’entrée. Le guide d’ondes intégré aux substrats (GIS) offre une technologie intéressante pour les réseaux d’alimentation d’antennes en termes de faible pertes par radiation, ce qui assure un très faible niveau d’interférences et d’effets parasitiques entre les circuits de GIS. Nous proposons dans ce travail plusieurs matrices de formation de faisceaux basées sur la technologie GIS. La thèse est présentée sous forme d’articles. Ce travail montre les étapes entreprises afin de mener à terme la conception, la fabrication, les mesures et l’évaluation de plusieurs topologies de la matrice de Butler. Nous verrons donc dans un premier temps les composants nécessaires au bon fonctionnement d’un tel système soit: les coupleurs 3 dB, les déphaseurs et les croisements. Le choix de la configuration sera justifié pour chacun de ces éléments. L’usage de simulateur (Ansoft HFSS) basé sur la méthode des éléments finis (une méthode à ondes complètes) sera nécessaire dans ce travail. Ce logiciel donne des résultats assez proches des essais expérimentaux. Trois matrices de Butler sont développées, la première à 77 GHz sans croisement, une deuxième est une structure à deux couches à 24 GHz et la troisième est une matrice complètement planaire avec un coupler 0 dB à 12.5 GHz.---------- ABSTRACT Automotive radar applications require components with high performance but low cost. This thesis presents the design of millimeter wave antennas feeding networks using the substrate integrated waveguide (SIW) technology, to satisfy the requirement of low cost and compactness in these radar applications.In a radar system the antenna define the width of covered area, the range, the angular discrimination and the filter noise generated by other sources. Generally smart antennas must be used to satisfy the specifications. The beam pointing can be achieved only by adjusting the phase of signals from different elements. For a choice of beam in a desired direction, a phase adjustment must be done. Switching matrices are used to provide phase distribution at output ports that is different for each input port. The substrates integrated waveguide (SIW) is a promising technology for the antenna feed networks in terms of low radiation and transmission losses with reduced interferences among SIW circuit elements. We propose in this work several beamforming matrices based on SIW technology. This thesis is presented in paper form. First of all, this work shows the steps taken to finalize the design, fabricate, measurement and evaluation of several Butler matrix topologies. We will see at first that the building components necessary for the proper functioning of such a network: the 3 dB couplers, phase shifters and crossovers. The choice of a configuration will be justified for each of these elements. An electromagnetic simulator (Ansoft HFSS) based on the finite element method (full-wave method) is used in this work. This software package would be able to yield results close to experimental counterparts. Three Butler matrices are developed, the first at 77GHz without crossover, the second is related to a two layer structure at 24 GHz and the third is completely made planar with a cross-over at 12.5 GHz. The Nolen matrix compared to Butler matrix has the advantages of being free from crossovers in the structure. The loads placed on unused ports in the Blass matrix do not appear in the Nolen matrix which increases efficiency. We propose two architectures, the first one is related to perpendicular configuration in Ku band while the second platform presents a parallel topology which shows a good performance over a broad band around 77 GHz

Microsystem technology for microwave applications at frequencies above 100 GHz

The rapid development of wireless technology today shows an increasing need for<br /><br />electromagnetic components operating at even higher frequencies. Higher frequencies offer wider bandwidth, higher spatial resolution and are needed for technologies such as automotive car radars, wireless media communication and body scanners.<br /><br />The biggest issues with developing high frequency components are the small dimensions needed. With the small dimensions, issues with connectivity and resolution of the structures have become difficult to handle at frequencies above 100 GHz. The most common fabrication method used is micro-milling in brass, however this is limited in its resolution and micro-milling is not a mass production method, thus making it expensive.<br /><br />This thesis aims to realize electromagnetic components at high frequencies, more specific above 100 GHz, with the help of microsystem technology. The thesis covers a background and history of the field, a discussion of the technologies used, and presents the fabricated devices, made with microsystem technology.<br /><br />In this thesis, gap waveguides ranging from 100-325 GHz, gap adapters, and transitions fabricated with microsystem technology have been explored. Three different materials: silicon, SU8, and carbon nanotubes, have been tested as base materials together with a gold surface, for a gap waveguide component. The silicon-based structure performed overall the best, while the SU8 process was less costly, the carbon nanotube based structure was determined to be the lossiest of these realizations. The knowledge obtained from these fundamental structures were used to fabricate and measure a ridge gap antenna prototype. A gap adapter was used to connect to the antenna, to reduce leakage without using damaging screws. The antenna, was fabricated in silicon for 100 GHz. A new transition, based on the knowledge of previous transitions was used to connect the waveguide flange to the feed of the antenna. The ridge gap antenna has a 15.5% bandwidth and a gain of 10.3 dBi matching perfectly the simulated design.<br /><br />The presented work in this thesis shows how microsystem technology can realize mass producible microwave components operating above 100 GHz

Enhancement of Millimeter-Band Transceivers with Gap Waveguide Technology

Mención Internacional en el título de doctorIt is known to all that year after year in modern society there is an urgent demand to consume wirelessly, and even stream ever larger multimedia content. High-frequency technologies have made it possible to go from transmitting analog voice and SMS text messages, to now transmitting live video in 4K quality from a mid-range smartphone. The way to measure these advances is by the bandwidth (Mb/s) reserved for each network user and the cost required to achieve it. To achieve even higher bandwidths, it is essential to improve signal coding techniques or increase the frequency of the signal, for example: to the mmWave bands (25GHz - 100 GHz), where these high-frequency techniques come into play. However, there is a frequency limit where current planar technology materials - such as the printed circuit boards used to build RF devices - are so lossy that they are not suitable at these mmWave frequencies. Current commercial solutions consist of guiding the electromagnetic energy with hollow metallic waveguides, but they suffer from the problem that as the frequency increases the diameter of these waveguides gets smaller and smaller, so manufacturing tolerances increase exorbitantly. Not to mention that they are usually manufactured in two parts, one upper and one lower, whose joints are not always perfect and produce energy losses. With these issues in mind, in 2009 the theory and basic science of a new electromagnetic energy guidance technology called Gap Waveguide was proposed, which is based on the use of metasurfaces constructed with periodic elements similar to a bed of nails. There are several implementations of this technology, but the three main ones are: Ridge, Groove and Inverted Microstrip Gap Waveguide. The latter is the most compatible with conventional planar manufacturing technologies and therefore the most cost-effective, although it also has drawbacks mainly in terms of losses when compared to the other versions. This thesis aims to deepen the study of the Inverted Microstrip guidance technology, its limitations and to develop with it some of the needed components in RF systems such as filters, diplexers, amplifiers, antennas, etc. Regarding the methodology for this thesis, a commercial simulation software for the analysis of antennas and components, CST Microwave Studio [1], has been used. AWR Microwave Office [2], a circuit simulator, has also been used to complement the simulations. On the other hand, there is a laboratory for the manufacture of prototypes in printed technology (with some limitations in terms of resolution) and the corresponding measurement laboratory, which includes network analyzers up to 40 GHz, spectrum analyzers and an anechoic chamber.This thesis arose under the Spanish Ministry of Science and Innovation (MINECO) and European Regional Development Fund (ERDF) project, called "Antenna for Mobile Satellite Communications (SATCOM) in Ka-Band by means of metasurfaces (2016-2019)", with reference TEC2016-79700-C2-2-R. Under this contract, the author signed an FPI research contract.Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan CarlosPresidente: Íñigo Cuiñas Gómez.- Secretario: Ángela María Coves Soler.- Vocal: Astrid Algaba Brazále

Subarray-Based Multibeam Antenna Frontend for Millimeter-Wave Hybrid Beamforming

With the paradigm shift from sub-6 GHz to millimeter-wave (mm-Wave) for wireless communications, beamforming becomes essential for mm-Wave access points to mitigate losses. Due to the small wavelength, a compact circuit could accommodate a large number of antenna elements. This favors the principle of beamforming to achieve high array-gain and spatial resolution through a large-scale N × M array. For such antenna frontends, full-digital beamforming circuitry requires N × M RF chains, which is unfeasible and energy inefficient. Likewise, a higher-order mm-Wave analog beamforming network is highly lossy to generate N × M beams. Hybrid beamforming addresses this dilemma by partitioning the beamforming between the analog and digital domains appropriately. For this purpose, the antenna frontend needs to be segmented into subarrays, such that the subarray-based analog beamspace patterns are digitally processed rather than processing element patterns individually. Thus, hybrid beamforming requires a suitable subarray-based N × M multibeam antenna frontend. In this thesis, a study of the subarray antennas is presented for hybrid beamforming operation. A simplified model is considered in which the analog beam-switching is performed in the azimuth plane (H-plane) and the digital beamspace beamforming in the elevation plane (V-plane). This is to reduce the number of RF chains as well as to achieve fine-tuned digital beam-steering in V-plane along with predefined analog switched-beams in H-plane. In this research work, the frequency band of 28 – 32 GHz is considered for prototyping purposes. For practical use at mm-Wave, the microstrip line technology is augmented with the perfect magnetic conductor (PMC) packaging. The fixed-beam and switched-beam subarrays with an order of n × m = 1 × 4, 2 × 2, and 4 × 4 are investigated. A dual-polarized aperture-coupled magneto-electric dipole antenna is designed as a single element with 20% bandwidth, ports' isolation better than 35 dB, cross-polarization less than -25 dB, and gain of 8 dBi. Using this element, a fixed-beam 4 × 4 dual-polarized subarray is designed that maintains a bandwidth of 16.7% at 30 GHz with a maximum gain of 19.3 dBi and symmetrical radiation patterns. The fixed-beam limitation of the 2n × 2m subarray leads to building the efficient switched-beam subarray antennas for hybrid beamforming. For this purpose, a 2 × 2 dual-polarized analog beamforming network is designed for 28-32 GHz. Two identical PMC packaged microstrip line networks, one for each polarization, are designed on a single substrate surface. However, to be processed for beamspace digital beamforming, this topology exhibits physical layout and array factor problems. Thus, further designs are investigated to meet the hybrid beamforming frontend requirements. To this end, as switched-beam subarrays for hybrid beamforming, two PMC packaged 4 × 4 Butler matrices are presented with a longitudinal layout and a folded layout for the end-fire and broadside radiation characteristics, respectively. The former design achieves a 5 GHz (28-33 GHz) bandwidth with return loss and isolation, both better than 15 dB. At 30 GHz, the insertion loss is 0.8 ± 0.3 dB, and antenna-ports' phase distributions are ±45° and ±135°. E-plane-flared horn antennas terminate the Butler matrix antenna-ports as a linear array. The double-ridge gap waveguide horn antenna is designed to reduce the scan loss within a subarray environment. The H-plane fan-beam switching covers ±42° with a maximum gain of 11.7 and 11.2 dBi for the inner (1R) and outer (2R) radiation beams. The latter novel topology of the folded Butler matrix is laid out for a compact tiled planar antenna frontend to accommodate a beamforming network beneath the antenna array's physical footprints. As compared to the conventional longitudinal layout, the size is reduced by more than 50 %. The PCB aperture-coupled antenna elements are integrated within the PMC packaged environment for a broadside radiation characteristic. The folded Butler matrix and antenna element are designed for a bandwidth of 4 GHz (28-32 GHz). The single antenna element's directivity is 5.22 dBi; whereas, for a 1 × 4 switched-beam subarray antenna, the directivities are 11.1 dBi and 10.6 dBi for 1R and 2R beams, respectively. Using Butler matrices-based 1 × 4 switched-beam subarrays, two types of multibeam antenna frontends with order N × M = 4 × 4 are constructed. Post-processing for the digital beamforming is applied over the subarray-based analog beamspaces. The first hybrid beamforming model maintains a scan range of ± 42o in the H-plane and ± 28o in the V-plane with BV × BH = 3 × 4 = 12 beams. Similarly, the second model maintains a scan range of ± 38o in the H-plane and ± 40o in the V-plane with BV × BH = 4 × 4 = 16 beams. As compared to full-analog two-dimensional (2-D) beamforming, these models are capable of fine-tuned beam-steering in the V-plane because the complex beamforming coefficients are not fixed but calculated digitally. Furthermore, compared to full-digital 2-D beamforming, it reduces the number of active RF chains from N × M to N