Dual-band antenna elements that support dual-polarization provide ideal performance for applications including space-based platforms, multifunction radar, wireless communications, and personal electronic devices. In many communications and radar applications, a dual-band, dual-polarization antenna array becomes a requirement in order to produce an electronically steerable, directional beam capable of supporting multiple functions. The multiple polarizations and frequency bands allow the array to generate multiple simultaneous beams to support true multifunction radar. Many of the applications in spaced-based systems and personal electronic devices have strict restraints on the size and weight of the antenna element, favoring a low-profile, lightweight device. The research performed in this dissertation focuses on the design of a dual-band, dual-polarized antenna element capable of operating as an isolated element or in an array environment. The element contains two concentric, dual-polarized radiators. The low band radiator is a shorted square ring antenna, and the high band radiator is a square ring slot. Each constituent element achieves circular polarization through the introduction of triangular perturbations into opposing corners of the radiating element. This technique has been shown to introduce two, near-degenerate modes in the structure that – when excited in phase quadrature – combine to form circular polarization. The perturbations allow circular polarized operation with only a single feed point. The sense of the circular polarization is determined by the location of the feed point with respect to the perturbations. Both senses of circular polarization are excited by the introduction of orthogonal feeds for each of the two radiating elements. Thus, dual-ban, dual-circular polarization is obtained. The element achieves a low-profile from its printed circuit board realization. The high band square ring slot is realized in stripline. The orthogonal feeding transmission lines are printed on opposing sides of an electrically thin dielectric layer to allow them to cross without physically intersecting. This thin feeding substrate is sandwiched between two dielectric layers of matched dielectric constant. A ground plane is located on the top and bottom of the sandwiched dielectric structure, and the top ground plane contains the square ring slot with perturbed corners. Slotted stripline structures have been shown in the literature to excite a parallel-plate mode that can degrade overall performance of the antenna. Plated through holes are introduced at the outer perimeter of the square ring slot to short out this parallel-plate mode. The plated through holes (also called vias) serve as the shorting mechanism for the low band microstrip shorted square ring radiator. This element also contains triangular perturbations at opposing corners to excite circular polarization with a single feed point. In this element, orthogonal probe feeds are present to excite both senses of circular polarization. A dual-band, dual-polarized antenna element was built, tested, and compared to simulations. The constructed element operated at two distinct industrial, scientific, and medical (ISM) frequency bands due to their popularity in low power communications. The antenna element was realized in a multilayer printed circuit layout. A complex design procedure was developed and submitted to a printed circuit board company who manufactured the antenna element. The s-parameters of the antenna were measured using a Network Analyzer, and the results show good agreement with simulations. The radiation and polarization characteristics were measured in a compact range facility. These results also agreed well with simulations. The measured results verify the simulation models that were used in the simulations and establish a confidence level in the feasibility of constructing this element. The dual-band, dual-polarization nature of this element was established through the construction and measurement of this element. A novel size reduction technique was developed that allows for significant reduction of the element's footprint. This size reduction facilitates the placement of this element within an array environment. The loading technique utilizes a structure analogous to a parallel-plate capacitor to drastically reduce the overall size of the low frequency shorted square ring. The loading structure uses a substrate that is separate from that of the radiating elements. This allows the load to use a high dielectric material to achieve a high capacitance without requiring the radiating elements to be printed on high dielectric material that is potentially expensive and lossy at microwave frequencies. The two frequency bands were selected to be in separate industrial, scientific, and medical (ISM) bands. These frequency bands are increasingly popular in low power communication devices because unlicensed operation is permitted. The 2.45 GHz and 5.8 GHz ISM bands are commonly used for applications including Bluetooth technology, multiple 801.11 protocol, cellular phone technology, and cordless phones. The ISM bands were chosen for this antenna element due to their popularity, but this antenna is not restricted to these bands. The frequency ratio can be altered by controlling the dielectric constant used in the printed circuit board design, the parameters of the capacitive loading structure, and the size of the constituent elements that are used. After the size reduction technique is applied, the dual-band, dual-polarized elements can be placed in an array environment resulting in an array capable of generating both senses of circular polarization in the two, distinct ISM bands. This provides an aperture capable of supporting multiple functions. Depending on the applications required, the frequency bands of the antenna element can be altered to suit the particular system needs. The array analysis performed in this dissertation used a unique hybrid calculation technique that utilizes nine active element patterns to represent the patterns of the individual elements within a large antenna array. A common first look at array performance is achieved by multiplying the element pattern of an isolated element by an array factor containing the contributions of the geometrical arrangement of the antenna elements. This technique neglects mutual coupling between elements in the array that can alter the impedance match and radiation characteristics of the elements in the array. The active element pattern defines the radiation pattern of a given element in an array when all other elements are terminated in a matched impedance load. The active element pattern is unique for each element in an array. When these patterns are summed, the exact array pattern is obtained. While this technique has the advantage of accuracy, it is not ideal because it requires the simulation, calculation, or measurement of the pattern for each element in the array environment. The technique developed in this dissertation uses only nine active element patterns. These elements are then assigned to represent the active element patterns for all elements in the array depending on the geometrical region where the given element resides. This technique provides a compromise between the speed of using a single element pattern and the accuracy of using the unique active element pattern for each element in the array. The application of these two concentric, coplanar radiators along with the capacitive loading technique provides a unique contribution to the field of antenna engineering. The majority of dual-band antenna elements in the literature operate with a single polarization in each band. The ones that operate with dual-polarization in each band are typically limited to dual-linear polarization. Circular polarization is preferable to linear in many applications because it allows flexible orientation between the transmitting antenna and receiving antenna in a communications system, while also mitigating multipath effects that lead to signal fading. The ability to operate with two, orthogonal senses of circular polarization allows a system to reuse frequencies and double system capacity without requiring additional bandwidth. The uniqueness of this element lies in its ability to provide dual-circular polarization in two separate frequency bands for an individual element or an antenna array environment. The arrangement of the two element geometries with the addition of the novel capacitive loading technique is also unique. The performance of this element is achieved while maintaining the light weight, low profile design that is critical for many wireless communications applications. This dissertation provides a detailed description of the operation of this dual-band, dual-polarized antenna element. The design of the constituent elements is discussed for several polarization configurations to establish an understanding of the building blocks for this element. The dual-band, dual-polarized element is presented in detail to show the impedance match, isolation, and axial ratio performance. The capacitive loading technique is applied to the dual-band, dual-polarized element, and the performance with the loading in place is compared to the performance of the unloaded element. Next, there is an in-depth description of the array calculation technique that was developed to incorporate mutual coupling effects into the array calculations. This technique is then applied to the dual-band, dual-polarized array to show the performance of several array sizes. / Ph. D.

An X band dual polarized slotted waveguide antenna array is designed with very high polarization purity for both horizontal and vertical polarizations. Horizontally polarized radiators are designed using a novel non-inclined edge wall slots whereas the vertically polarized slots are implemented using broad wall slots opened on baffled single ridge rectangular waveguides. Electromagnetic model based on an infinite array unit cell approach is introduced to characterize the slots used in the array. 20 by 10 element planar array of these slots is manufactured and radiation fields are measured. The measurement results of this array are in very good accordance with the simulation results. The dual polarized antenna possesses a low sidelobe level of -35 dB and is able to scan a sector of &plusmn / 35 degrees in elevation. It also has a usable bandwidth of 600 MHz.

Dans les systèmes de communication et de détection sans fil, l'antenne est un élément indispensable pour transformer l'énergie électrique en ondes électromagnétiques rayonnée dans l'espace, et vice versa. Les antennes sont utilisées dans de nombreux dispositifs militaires et civils, tels que les radars (SAR, secteur automobile, détection de débris, etc.), les instruments biomédicaux, les systèmes de télécommunication (téléphones mobiles, stations de base) pour les communications point à multi-point ou point à point par exemple. Les antennes jouent aussi un rôle essentiel pour le développement de futurs réseaux connectés reliant plusieurs appareils à des utilisateurs en temps réel, par exemple pour l'Internet des objets (IoT). Les réseaux transmetteurs sont une solution attrayante pour de nombreuses applications telles que les communications par satellite (Satcom) ou les futurs réseaux 5G. L'architecture des antennes à réseau transmetteur les rend extrêmement compétitifs comparés aux réseaux phasés par exemple grâce à leur alimentation par onde d’espace et car ils ne souffrent pas du blocage induit par la source primaire, comme c’est le cas pour les réseaux réflecteurs ou les antennes à réflecteur. Grâce à leur fonctionnement en mode transmission, les réseaux transmetteurs peuvent être également facilement montés sur des plates-formes mobiles.Les applications Satcom en bande Ka constituent le secteur applicatif majeur de cette thèse. Cette bande fournit un débit de données élevé à la fois pour les liaisons descendantes et les liaisons montantes, en remplacement des systèmes actuels en bande Ku. Dans ce contexte, il convient aussi de prêter une attention particulière aux communications avec des plates-formes mobiles, par exemple les trains à grande vitesse, les avions, etc., ce qui nécessite de mettre au point des antennes à balayage de faisceau. De nombreuses propriétés avancées sont exploitées depuis ces dernières années pour accroître les débits et la flexibilité des systèmes de communication sans fil, par exemple la polarisation circulaire, la double polarisation, le fonctionnement multi-fréquence ou large bande, le dépointage électronique de faisceau. Pour réduire les coûts, des preuves de concept de réseaux transmetteurs non diélectriques sont également proposées. Cette thèse s’est déroulée dans le cadre du projet ANR TRANSMIL (Reconfigurable TRANSmitarrays for beam steering and beam forming at MILlimetre wave). Les objectifs de cette thèse sont de proposer de nouvelles architectures de réseaux transmetteurs fonctionnant en bande Ka en liaison descendante (de 17,7 GHz à 21,2 GHz) et en liaison montante (de 27,5 GHz à 31 GHz). Différents prototypes ont été conçus et fabriqués afin de valider les concepts proposés en bande X et en bande Ka. Un bon accord entre les résultats numériques et mesurés a été obtenu systématiquement. En particulier, les réseaux transmetteurs à double polarisation que nous avons conçus en bande X présentent un gain de 25 dBi et une bande passante à 3 dB de 20% à 10 GHz. Ces propriétés sont indépendantes de la polarisation du champ rayonné, ce qui signifie que des faisceaux de polarisation linéaire orthogonale peuvent être rayonnés indépendamment dans des directions différentes. Un réseau transmetteur bi-bande fonctionnant en bande Ka a également été mis au point. Sa bande passante à 3 dB est de 10% autour des fréquences centrales (19,5 GHz et 29 GHz) et son efficacité de rayonnement atteint 60%. D’autres concepts ont également été étudiés (réseaux transmetteurs sans diélectrique, réseau transmetteur reconfigurable). / Transmitarray is an attractive solution for front-end devices in the next generation of communications (5G). The spatial-fed architecture of transmitarray antennas can compete with phase-arrays due to the absence of feeding network and with reflectarrays since they do not suffer from feed blockage. Thanks to their operation in transmission mode, transmitarrays can be easily mounted on platforms for outdoor environment applications. With mature printed-circuit board technology, there are unstoppable experiments in various frequency bands from cm-wave to mm-wave and up to terahertz in upcoming years for potential applications. Many advanced properties are exploited in transmitarrays in recent years to meet high demands of communications facilities, for example, circular-polarization, dual-/multi-polarization or frequencies through many techniques. Some experiments are consid-ered to validate eligibility of this antenna type in commercial services or military missions, namely electronically steering beam, broad bandwidth, etc. In terms of cost reduction and rigidity, non-dielectric prototypes are also proposed. The Ka-band Satcom applications are the main objective of this thesis through trans-mitarray solution. This band provides high data rate for both down-link and up-link in replacement of the current Ku-band systems with miniaturized module in next dec-ades. Hence, it is worth to pay attention to communications for moving platforms, for example, high-speed trains, planes, etc.

Satellite communication (Satcom) services are used worldwide for voice, data, and video links due to various appealing features. Parabolic reflector antennas are typically used to serve a cost effective scheme for commercial applications. However, mount degradation, roof sag, and orbital decay motivate the need for beam steering. Limited scan range beam steering opens a third option for electronic beam steering with lower cost than full aperture phased arrays and higher tracking speed and accuracy than mechanical-only steering.Multiple high efficiency passive patch array feeds were designed, fabricated, and measured, including a 2x2 MSA array, a stacked shorted annular patch antenna, and an SIW-fed hexagonal array feed based on PTFE material, achieving performance comparable to a horn feed. For multiband dual polarization applications, passive MSA feed solutions are also provided. Multiple MSA array feeds with high isolation were designed for dual band dual polarization applications. More functionality can be realized with multi-layer PCB techniques for complex communication scenarios.Limited scan range electronic beam-steering with a parabolic reflector fed by an active array feed which only needs gain control was demonstrated experimentally, leading to a low cost and effective solution for active beam scanning. A cost-effective flat-panel phased array with limited scan range electronic beam-steering was proposed by tiling high efficiency 4x4 passive subarrays and performing beam scanning at the tile level. The sidelobe issue was also investigated to comply with the pattern mask requirement set by FCC.To enable better use of circularly polarized (CP) MSAs for electronically beam-formed antenna systems, the impact of mutual coupling on the performance of high-sensitivity dual-polarized receivers for satellite communications applications was analyzed. A new analysis method for intrinsically dual-CP MSAs based on an equivalent circuit model and Jones matrices was proposed and validated to overcome the port isolation challenge. The model provides accurate estimates of impedances and S-parameters, as well as field parameters such as axial ratio. The feasible region for XPI and impedance mismatch factor is found for dual CP antennas. The circuit model enables multiple useful applications. Effective decoupling and matching schemes was proposed and demonstrated, leading to a high isolation, good match, and wide AR bandwidth dual CP MSA for satellite communications.

Existing unified numerical electromagnetic methods are often unable to analyze electrically large structures due to the amount of memory and processing power required, necessitating approximate analyses with limited applicability. In this research a hybrid modeling methodology is adopted to solve these complex problems more efficiently than unified numerical methods and more accurately than analytical methods. Electromagnetic modeling problems are divided into two or more levels of scale. Each level analyzes a specific level of detail and only promotes the required information to the next level. The method is demonstrated by successful application to three important problems: (1) remote sensing of snow, (2) modeling an optical Bragg resonator, and (3) modeling the MIMO wireless channel. First, complex snow media is analyzed with a hybrid FDTD/radiative transfer model. FDTD is used to compute phase matrices and extinction coefficients required for radiative transfer. Comparison with exact analytical methods proves the validity of the FDTD method for modest domain sizes ([5λ^3]) and number of Monte Carlo realizations (32). The method is used to illustrate a penetrating sphere model, which is not possible with existing analysis techniques. Backscatter from the resulting model is about 3 times higher than that of existing dense-medium theories, underlying the importance of exact characterization of the media. Second, a hybrid FD/FDTD/S-parameter analysis is developed to model a large (10^4 section) optical Bragg resonator: a simple FD method computes propagation constants and field profiles, FDTD analysis provides reflection and transmission coefficients for the single section, and S-parameter analysis combines the sections to obtain the complete device response. A detailed study on error suggests that the method provides better than 2% accuracy in reflection and transmission response. Third, a hybrid electromagnetic/SVA model is developed to study the indoor MIMO wireless channel. A MIMO measurement platform is discussed for simultaneous probing of up to 16 transmit and receive antennas, which was required to assess the validity of later modeling. FDTD or MOM antenna analysis coupled with the SVA model gives capacity predictions which match measured data. The model is used to explore the impact of antenna spacing, directivity, and polarization on channel capacity. Closely spaced antennas lead to an approximate halving of receive power. Directivity effectively doubles receive power for aligned transmit and receive. Dual polarization increases system capacity anywhere from 10% to 70%, depending on the spacing of elements and the amount of multipath richness. This analysis of MIMO systems underlines the need for models that describe both multipath richness and average receive power.

In the sub-THz frequency range, the geodesic lens can realize low losses and beam scanning capability with high gain and high aperture efficiency due to its fully metallic property and rotational symmetry. Therefore, in high-frequency applications, a geodesic lens is considered a more promising solution in comparison to phased arrays or other beamforming techniques. To realize dual polarization for geodesic lenses, a polarization rotator using fully metallic screens can be placed at the lens aperture to increase the channel capacity. In this thesis, we propose a dual-polarized fully metallic geodesic lens antenna with the operation frequency centered at 120 GHz. The proposed design contains two layers of geodesic lenses and two polarization rotators placed in their respective apertures with ±45° polarization. By using a twist waveguide for the feeding, we eliminate the leakage caused by the air gap between the metal plates. The simulation results show that the dual-polarized lens can achieve an angular scanning range of ±60° and its scanning loss is 0.6 dB, with an aperture efficiency of 90%. Finally, we propose a prototype design with mechanical considerations to ensure robustness in future manufacturing, assembly, and testing. / Geodetiska linser kan tillämpas åt frekvenser under THz för att realisera låga förluster och strålscanningskapacitet med både hög förstärkning och apertureffektivitet, detta på grund av dess fullt metalliska egenskaper samt rotationssymmetri. I högfrekventa tillämpningar anses därför en geodetisk lins vara lovande i jämförelse med en fasstyrda gruppantenn eller andra strålformningstekniker. Ytterligare så kan polarisationsrotatorer med helt metalliska skärmar kan placeras vid linsöppningen för att realisera korspolariserade fält samt öka kanalkapaciteten hos geodetiska linser. I denna avhandling föreslårs en justerbar korspolariserad samt fullt metallisk geodetisk linsantenn centrerad runt 120 GHz. Den föreslagna designen innehåller två lager geodetiska linser och två polarisationsrotatorer placerade i sina respektive utgångar med respektive polarisatonsförskjutning på ±45°. Genom att använda en vriden vågledare för matningen så eliminerars läckaget som normalt följer av luftgapet mellan metallplattorna. Simuleringsresultaten visar att den korspolariserade linsen kan uppnå ett avsökningsområde inom vinklar ±60° men en skanningsförlust på 0,6 dB, detta med en apertureffektivitet på 90%. Slutligen föreslår vi en prototyp med hänsyn till mekaniska aspekter för att säkerställa robusthet i framtida tillverkning, montering och testning.

As advances in thin films are made there is a parallel requirement to develop equipment capable of measuring their properties accurately and consistently. In addition there is a need to understand the parameters that are measured. Typical DPI measurements allow both the refractive index (related to density) and the thickness of the adsorbed layer to be calculated with relatively few assumptions, to a very high precision in real time. This thesis presents the research undertaken to develop multiple path length dual polarisation interferometry (MPL-DPI) and absorption enhanced dual polarisation interferometry (AE-DPI). In addition research is presented that can be used to improve the interpretation of the measured parameters for inhomogeneous films and uniaxial films. The new Interferometric technique MPL-DPI allows the thickness and refractive index of in situ and ex-situ coated ultra-thin films to be measured. The procedures and the mathematics required to calculate the properties of films have been described and the technique verified. The technique was demonstrated using films of PMMA, where good agreement was found with complementary techniques. Furthermore, some key features of MPL-DPI were demonstrated using the measurements of interfacially grafted acrylic acid. The absorption enhanced DPI uses the attenuation of the light within the waveguide, due to the light absorbing properties of a film on its surface. As the composition of a film changed, it was shown that the refractive index and extinction coefficients could be used to separate the mass of the components of the film that absorbed light, from the components of the film that did not. With the use of a semi-uniaxial model, the extra data from the attenuation in two polarisations was used to fit the extraordinary and ordinary extinction coefficients. The extraordinary and ordinary extinction coefficients were used to demonstrate that molecular orientation could be implied. The influence that an inhomogeneous film has on the measured thickness, refractive index and extinction coefficient fitted by homogeneous models were investigated. Formulas are presented to explain the thickness, refractive index and extinction coefficient of the measured film. A formula for the total mass per unit area that uses the refractive index was created to account for films that contain molecules of different refractive index increments (dn/dc's). To separate the mass of the individual molecular species from the total mass per unit area, formulas that use the extinction coefficient were derived so molecules that absorb light could be separated from those that do not. The mass calculated from the refractive index and the mass calculated from the extinction coefficient were also examined for uniaxial films. For uniaxial films both measures of the adsorbed mass were found to be relatively accurate and benefited from a partial cancellation of errors. The accuracy of the measurements made by dual polarisation interferometry technology is systematically examined throughout this thesis. Improvements in the calibration routines are suggested and a procedure for the identification and reduction of errors in the phase and contrast is demonstrated.

本研究は, 広帯域直交偏波共用低交差偏波特性, 偏波変換特性および任意の反射位相差を有する高性能・高機能リフレクトアレー共振素子の開発を行い, 設計・試作したリフレクトアレーアンテナの放射特性の数値的及び実験的検討の研究成果をまとめたものである. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University