Although small spacecraft are small in size and light in weight compared to the conventional satellites, they can offer lots of possibilities for space exploration, scientific observation, data collection and telecommunication. Also, they cost a lot less money than the conventional satellites, and the scientific missions can be planned in a relatively short period of time by using the COTS (Commercial Off-The-Shelf) materials. However, there is a big challenge for the small spacecraft that is the limited surface area of the small spacecraft and the outnumbered components to be mounted on the surface of the small spacecraft. The most obvious one is that the competition for the limited real estate between the antenna and solar cells. UAVs, also known as drones, have become so popular that it is not only used for military and scientific applications, but also they are available for recreational use for ordinary people. Although they are getting smaller in size so that one can put them in his pocket or on his palm, they are becoming multifunctional, which requires more sensors to be mounted on the surface of the drone to achieve its multifunctionality. For example, a recreational drone can not only take pictures and videos, but also it can transmit the picture or video in real time to the operator, which needs a camera to take the picture or videos and needs an antenna to transmit the recorded data to the operator. This requires that the limited surface area needs to be efficiently used in order to accommodate the multiple needed components. This thesis presented a faster, better and cheaper way of inkjet printing conformal antennas on the cover glass of the solar cells of the small spacecraft or on the wing or other parts of the UAV body to integrate the antenna with the solar panels of the CubeSats or with or directly printing the antenna on the UAV body to efficiently use the limited real estate. Several meshed and solid patch antennas printed on a space certified AF32 glass substrate using the printing procedure outlined in this thesis and measured to verify the effectiveness of the inkjet printing procedures. A high gain reflectarray with optical transparency of 95% was inkjet printed on space certified AF32 glass and BOROFLOAT glass and measured to verify the antenna performance and solar panel efficiency. Measurement results showed that the inkjet printed reflectarray integrated on top of the solar panel has a gain of 21.5 dB. The solar panel efficiency was dropped by around 6% due to the inkjet printed reflectarray on glass. A simple conformal dual-band antenna for UAV application was designed with ANSYS HFSS and fabricated in the lab using a foam substrate. The measured antenna performances agreed well with the simulation results. This dual-band antenna also can be inkjet printed directly on the wing or other parts of the UAVs using the printing techniques discussed in this thesis.

Yes / This paper describes a hybrid computational method which efficiently models the interaction between a small antenna placed in proximity with the human body. Results for several test cases of placed in different locations on the body are presented and discussed. The near and far fields were incorporated into the study to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power is also provided. The antennas are assumed to be operating over the 2.4 GHz and 5.2 GHz WLAN frequencies.

Yes / A four-element compact dual-band patch antenna having a common ground plane operating at 28/38 GHz is proposed for millimeter-wave communication systems in this paper. The multiple-input-multiple-output (MIMO) antenna geometry consists of a slotted ellipse enclosed within a hollow circle which is orthogonally rotated with a connected partial ground at the back. The overall size of the four elements MIMO antenna is 2.24λ × 2.24λ (at 27.12 GHz). The prototype of four-element MIMO resonator is designed and printed using Rogers RT Duroid 5880 with εr = 2.2 and loss tangent = 0.0009 and having a thickness of 0.8 mm. It covers dual-band having a fractional bandwidth of 15.7% (27.12–31.34 GHz) and 4.2% (37.21–38.81 GHz) for millimeter-wave applications with a gain of more than 4 dBi at both bands. The proposed antenna analysis in terms of MIMO diversity parameters (Envelope Correlation Coefficient (ECC) and Diversity Gain (DG)) is also carried out. The experimental result in terms of reflection coefficient, radiation pattern, gain and MIMO diversity parameter correlates very well with the simulated ones that show the potential of the proposed design for MIMO applications at millimeter-wave frequencies. / This work is supported by the Moore4Medical Project, funded within ECSEL JU in collaboration with the EU H2020 Framework Programme (H2020/2014-2020) under Grant Agreement H2020-ECSEL-2019-IA-876190, and Fundação para a Ciência e Tecnologia (ECSEL/0006/2019). This work is also funded by the FCT/MEC through national funds and when applicable co-financed by the ERDF, under the PT2020 Partnership Agreement under the UID/EEA/50008/2020 Project.

Multi band technology helps in getting multiple operating frequencies using a single microwave device. This thesis presents the design of dual and tri band microwave devices using coupled transmission line structures. Chapter 2 presents the design of a novel dual band transmission line structure using coupled lines. In chapter 3, Design of a dual band branch line coupler and a dual band Wilkinson power divider are proposed using the novel dual band transmission line structure presented in the previous chapter. In chapter 4, Design of a tri band transmission line structure by extending the dual band structure is presented. The Conclusion and future work are presented in chapter 5.

The thesis represents the design for dual-band quarter wavelength and half wavelength microstrip transmission line. Chapter 2 proposed the design of a novel dual-band asymmetric pi-shaped short-circuited quarter wavelength microstrip transmission line working at frequencies 1GHz and 1.55 GHz for 50Ω transmission line and at frequencies 1GHz and 1.43GHz for 60Ω transmission line. Chapter 3 proposed the design of a novel dual-band quarter wavelength microstrip transmission line with asymmetrically allocated open stubs and short-circuited stubs working at frequencies 1GHz and 1.32GHz. Chapter 4 proposed the design of dual-band pi-shaped open stub half wavelength microstrip transmission line working at frequencies 1GHz and 2.07GHz. Numerical simulations are performed both in HyperLynx 3D EM and in circuit simulator ADS for all of the proposed designs to measure the return loss (S11) and insertion loss (S12) in dB and phase response for S12 in degree.

Le medium sans fil est une ressource partagée et limitée. Les normes sans fil actuelles partagent toujours le principe de partage du medium Half-Duplex: la transmission et la réception de signaux sont effectuées dans deux intervalles de temps distincts ou deux bandes de fréquences différentes. En outre, l'émetteur-récepteur ne peut émettre et recevoir qu’un signal à la fois. Cette thèse suit une autre approche: au lieu de partager le support avec le principe de Half-Duplex, toute la bande de fréquence autorisée est partagé pour la transmission et la réception simultanée, approche qui est appelée Full-Duplex. Dès lors, on peut concevoir une architecture d'un émetteur-récepteur radio flexible à large bande pour traiter deux types de signaux différents à la fois. Pour approcher cet objectif, nous utilisons une méthode de suppression active analogique de l’auto-interférence (AARFSIC) et l'annulation active numérique d'auto interférence dans le domaine temporel (ADSICT) pour annuler la forte auto-interférence (SI) induite par le principe Full-Duplex. Basé sur la radio Full-Duplex, nous proposons un système flexible Dual-Band (FDDB) émetteur-récepteur radio OFDM-Full Duplex en la combinant avec un front-end RF double bande. S'appuyant sur ces principes, nous exposons trois contributions principales: Nous présentons une technique d’annulation analogique de l’auto-interférence (ASIC), qui peut annuler complètement l’auto-interférence à trajet direct ou multi-trajets, basée sur la combinaison des méthodes AARFSIC et DSICT. Ensuite, nous présentons la conception et l'évaluation d'une radio OFDM Full-Duplex, y compris l'analyse et la qualification de l'impact du bruit thermique et du bruit de phase sur les performances du système. Enfin, nous développons une radio dual-bande FDDB OFDM qui peut fonctionner sur deux fragments de spectre séparés. Afin d'éliminer l'impact du déséquilibre I/Q sur la radio FDDB, une méthode d’estimation des déséquilibres I/Q et de compensation, simple mais efficace, est présentée. La simulation au niveau système menée avec ADS et Matlab montre que cette méthode peut effectivement compenser des déséquilibres I/Q aussi bien élevés que faibles. / The wireless medium is a shared and limited resource. Current wireless standards always share the medium with Half-Duplex principle: the transmission and reception of signals are done in two separate time slots or two different frequency bands. Besides, the transceiver can only transmit and receive one signal at a time. This dissertation takes an alternate approach: Instead of sharing the medium with Half-Duplex principle, the entire licensed frequency band is shared for simultaneous transmission and reception, which we call Full-Duplex. Besides, the design concept for a wideband flexible radio transceiver can process two different types of signals at a time. To approach this goal, we use an active analog radio frequency self-interference cancellation (AARFSIC) method or a combination scheme of the AARFSIC and active digital self interference cancellation in time domain (ADSICT) to cancel the strong self-interference (SI) induced by the Full-Duplex principle. Based on the Full-Duplex radio, we propose a flexible Full-Duplex Dual-Band (FDDB) OFDM radio transceiver by combining it with a Dual-Band RF front-end. Building on these, we make three main contributions: We present an active self-interference cancellation (ASIC) scheme, which can cancel both the strong one-path and multi-path SI completely, based on the combination of the AARFSIC and DSICT. Next, we introduce the design and evaluation of a Full-Duplex OFDM radio, including the analysis and qualification of the impact of the thermal noise and phase noise on the system performance. Finally, we develop a FDDB OFDM radio that can work on two separate spectrum fragments. In order to eliminate the impact of the I/Q imbalance on the FDDB radio, a simple but practical digital I/Q imbalance estimation and compensation method is presented. The system level simulation conducted with ADS and Matlab software shows that this method can effectively compensate both high and low I/Q imbalance.

Este trabalho visou ao desenvolvimento de antenas de ressoador dielétrico de banda dupla em frequências de micro-ondas por meio do estabelecimento de uma metodologia de projeto para as mesmas e da proposição de configurações inéditas de antenas desse tipo. Estudos realizados sobre antenas de ressoador dielétrico e sobre suas técnicas de projeto forneceram a base para a elaboração de um procedimento de projeto para antenas de banda dupla que explora a flexibilidade das antenas de ressoador dielétrico. Empregando-se esse procedimento de projeto, duas antenas com configurações originais foram desenvolvidas para operar em frequências de micro-ondas. Uma delas é uma antena de ressoador dielétrico cilíndrica sobre plano de terra, destinada a operar nas frequências centrais de 3,94 GHz e de 5,42 GHz, com diagrama de radiação direcional e polarização circular na primeira banda de operação e com diagrama de radiação omnidirecional e polarização linear na segunda. A outra antena consiste em uma antena de ressoador dielétrico cilíndrica sobre substrato dielétrico aterrado, cujas frequências centrais de operação são 3,99 GHz e 6,20 GHz, com diagrama de radiação direcional e polarização circular em ambas as bandas de operação. O projeto das duas antenas também levou a contribuições novas adicionais em alguns temas específicos relacionados: estruturas de excitação para antenas de ressoador dielétrico, circuitos acopladores híbridos de 90° de banda dupla, circuitos de alimentação para antenas de banda dupla e modelos matemáticos para o ressoador dielétrico cilíndrico isolado no espaço livre. Os comportamentos previstos teoricamente para as antenas projetadas são confirmados por meio de resultados obtidos por simulação eletromagnética e por medição experimental, o que indica a validade das hipóteses adotadas, das configurações de antena propostas e da metodologia de projeto concebida, demonstrando também a flexibilidade desta para variadas especificações de antena. Os avanços obtidos com este trabalho e as melhorias que podem ser efetuadas sobre o mesmo são identificados examinando-se resultados recentemente publicados na literatura técnica. Este trabalho foi realizado na forma de uma pesquisa de doutorado sanduíche, desenvolvida parcialmente na University of Houston sob a supervisão do Prof. Stuart A. Long. / This work aimed at the development of microwave dual-band dielectric resonator antennas by means of establishing a design methodology for them and of proposing novel configurations of this antenna type. Studies on dielectric resonator antennas and on their design techniques provided the ground for elaborating a design procedure for dual-band antennas that exploits the flexibility of dielectric resonator antennas. By employing this design procedure, two antennas with original configurations have been developed for operation at microwave frequencies. One of them is a cylindrical dielectric resonator antenna on a ground plane, intended for operation at the center frequencies of 3.94 GHz and 5.42 GHz, with a directional radiation pattern and circular polarization in the first operating band and with an omnidirectional radiation pattern and linear polarization in the second one. The other antenna consists of a cylindrical dielectric resonator antenna on a grounded dielectric substrate, whose operating center frequencies are 3.99 GHz and 6.20 GHz, with a directional radiation pattern and circular polarization in both operating bands. The design of the two antennas also led to additional new contributions in some related specific subjects: excitation structures for dielectric resonator antennas, dual-band 90°-hybrid couplers, feeding circuits for dual-band antennas, and mathematical models for the cylindrical dielectric resonator isolated in free space. The behaviors theoretically expected for the designed antennas are confirmed by means of results obtained from electromagnetic simulation and from experimental measurements, which indicates the validity of the assumed hypotheses, of the proposed antenna configurations and of the conceived design methodology, also demonstrating the flexibility of the latter for various antenna specifications. The advances obtained with this work and the improvements that can be made on it are identified by examining results recently published in the technical literature. This work was carried out as a sandwich doctoral research, developed at the University of Houston under the supervision of Prof. Stuart A. Long.

Este trabalho visou ao desenvolvimento de antenas de ressoador dielétrico de banda dupla em frequências de micro-ondas por meio do estabelecimento de uma metodologia de projeto para as mesmas e da proposição de configurações inéditas de antenas desse tipo. Estudos realizados sobre antenas de ressoador dielétrico e sobre suas técnicas de projeto forneceram a base para a elaboração de um procedimento de projeto para antenas de banda dupla que explora a flexibilidade das antenas de ressoador dielétrico. Empregando-se esse procedimento de projeto, duas antenas com configurações originais foram desenvolvidas para operar em frequências de micro-ondas. Uma delas é uma antena de ressoador dielétrico cilíndrica sobre plano de terra, destinada a operar nas frequências centrais de 3,94 GHz e de 5,42 GHz, com diagrama de radiação direcional e polarização circular na primeira banda de operação e com diagrama de radiação omnidirecional e polarização linear na segunda. A outra antena consiste em uma antena de ressoador dielétrico cilíndrica sobre substrato dielétrico aterrado, cujas frequências centrais de operação são 3,99 GHz e 6,20 GHz, com diagrama de radiação direcional e polarização circular em ambas as bandas de operação. O projeto das duas antenas também levou a contribuições novas adicionais em alguns temas específicos relacionados: estruturas de excitação para antenas de ressoador dielétrico, circuitos acopladores híbridos de 90° de banda dupla, circuitos de alimentação para antenas de banda dupla e modelos matemáticos para o ressoador dielétrico cilíndrico isolado no espaço livre. Os comportamentos previstos teoricamente para as antenas projetadas são confirmados por meio de resultados obtidos por simulação eletromagnética e por medição experimental, o que indica a validade das hipóteses adotadas, das configurações de antena propostas e da metodologia de projeto concebida, demonstrando também a flexibilidade desta para variadas especificações de antena. Os avanços obtidos com este trabalho e as melhorias que podem ser efetuadas sobre o mesmo são identificados examinando-se resultados recentemente publicados na literatura técnica. Este trabalho foi realizado na forma de uma pesquisa de doutorado sanduíche, desenvolvida parcialmente na University of Houston sob a supervisão do Prof. Stuart A. Long. / This work aimed at the development of microwave dual-band dielectric resonator antennas by means of establishing a design methodology for them and of proposing novel configurations of this antenna type. Studies on dielectric resonator antennas and on their design techniques provided the ground for elaborating a design procedure for dual-band antennas that exploits the flexibility of dielectric resonator antennas. By employing this design procedure, two antennas with original configurations have been developed for operation at microwave frequencies. One of them is a cylindrical dielectric resonator antenna on a ground plane, intended for operation at the center frequencies of 3.94 GHz and 5.42 GHz, with a directional radiation pattern and circular polarization in the first operating band and with an omnidirectional radiation pattern and linear polarization in the second one. The other antenna consists of a cylindrical dielectric resonator antenna on a grounded dielectric substrate, whose operating center frequencies are 3.99 GHz and 6.20 GHz, with a directional radiation pattern and circular polarization in both operating bands. The design of the two antennas also led to additional new contributions in some related specific subjects: excitation structures for dielectric resonator antennas, dual-band 90°-hybrid couplers, feeding circuits for dual-band antennas, and mathematical models for the cylindrical dielectric resonator isolated in free space. The behaviors theoretically expected for the designed antennas are confirmed by means of results obtained from electromagnetic simulation and from experimental measurements, which indicates the validity of the assumed hypotheses, of the proposed antenna configurations and of the conceived design methodology, also demonstrating the flexibility of the latter for various antenna specifications. The advances obtained with this work and the improvements that can be made on it are identified by examining results recently published in the technical literature. This work was carried out as a sandwich doctoral research, developed at the University of Houston under the supervision of Prof. Stuart A. Long.

Dielectric resonators offer high-Q (low loss) characteristics which make them ideal for filters with narrow bandwidth and low insertion loss specifications. They are mainly used in satellite and wireless system applications. Such applications desire the highest performance filters with the lowest amount of size and mass, which has been the main motivation for size reduction techniques invented over the past three decades for these filters. In addition with the emergence of different communication system technologies, several bands are now required to be supported by a single front-end, calling for emergence and development of dual-band and multi-band filters. To date few work has been done in the area of dual-band dielectric resonator filters. Dielectric resonators filters are important components in many communication systems, when a group of such filters are brought together to perform multiplexing of RF channels. These multiplexer systems tend to be fairly complex and bulky in design, and there is strong desire to reduce their size and mass to the maximum extent possible. Novel quadruple-mode, dual-mode, and dual-band filters as well multiplexers are presented in this thesis. The first ever quadruple-mode dielectric resonator filter using the simple cylinder structure is reported in this work. A cylindrical dielectric resonator sized appropriately in terms of its diameter and height is shown to operate as a quadruple-mode resonator, which is achieved by having two mode pairs of the structure resonate at the same frequency. Single-cavity, quad-mode filters and higher order 4n-pole filters are realizable using this quad-mode cylindrical resonator, offering significant size reduction for dielectric resonator filter applications. The structure of the quad-mode cylinder is then simplified by cutting lengthwise along the central axis of the cylinder, to produce a half-cut cylinder suitable for operation in a dual-mode regime. Novel dual-mode, 2n-pole filters are realizable using this half-cut cylinder, by making the two resonances equal in frequency. The dual-mode half-cut filter is shown to be a strong contender for replacing existing dual-mode filters used in satellite and wireless applications, as it offers superior size and mass characteristics. By making the resonances unequal in frequency, novel dual-band filters and multiplexers are further realizable, by carrying separate frequency bands on different resonant modes of the structure. The first true orthogonal mode dual-band dielectric resonator is presented in this work, using the half-cut structure. Multiplexers are also derived from these dual-band resonators, which greatly reduce size and mass of many-channel multiplexers at the system level, as each two channels are overloaded in one physical branch. Full control of center frequencies of resonances, input and inter-resonator couplings are achievable, allowing realization of microwave filters with different bandwidth, frequency, and return loss specifications, as well as advanced filtering functions with prescribed transmission zeros. Spurious performance of the half-cut cylinder can also be improved by cutting one or more through-way slots between opposite surfaces of the resonator. Size and mass reduction achieved by using the full and half-cut resonators described in this thesis, provide various levels of size reduction in microwave systems, both device and system level.

Dielectric resonators offer high-Q (low loss) characteristics which make them ideal for filters with narrow bandwidth and low insertion loss specifications. They are mainly used in satellite and wireless system applications. Such applications desire the highest performance filters with the lowest amount of size and mass, which has been the main motivation for size reduction techniques invented over the past three decades for these filters. In addition with the emergence of different communication system technologies, several bands are now required to be supported by a single front-end, calling for emergence and development of dual-band and multi-band filters. To date few work has been done in the area of dual-band dielectric resonator filters. Dielectric resonators filters are important components in many communication systems, when a group of such filters are brought together to perform multiplexing of RF channels. These multiplexer systems tend to be fairly complex and bulky in design, and there is strong desire to reduce their size and mass to the maximum extent possible. Novel quadruple-mode, dual-mode, and dual-band filters as well multiplexers are presented in this thesis. The first ever quadruple-mode dielectric resonator filter using the simple cylinder structure is reported in this work. A cylindrical dielectric resonator sized appropriately in terms of its diameter and height is shown to operate as a quadruple-mode resonator, which is achieved by having two mode pairs of the structure resonate at the same frequency. Single-cavity, quad-mode filters and higher order 4n-pole filters are realizable using this quad-mode cylindrical resonator, offering significant size reduction for dielectric resonator filter applications. The structure of the quad-mode cylinder is then simplified by cutting lengthwise along the central axis of the cylinder, to produce a half-cut cylinder suitable for operation in a dual-mode regime. Novel dual-mode, 2n-pole filters are realizable using this half-cut cylinder, by making the two resonances equal in frequency. The dual-mode half-cut filter is shown to be a strong contender for replacing existing dual-mode filters used in satellite and wireless applications, as it offers superior size and mass characteristics. By making the resonances unequal in frequency, novel dual-band filters and multiplexers are further realizable, by carrying separate frequency bands on different resonant modes of the structure. The first true orthogonal mode dual-band dielectric resonator is presented in this work, using the half-cut structure. Multiplexers are also derived from these dual-band resonators, which greatly reduce size and mass of many-channel multiplexers at the system level, as each two channels are overloaded in one physical branch. Full control of center frequencies of resonances, input and inter-resonator couplings are achievable, allowing realization of microwave filters with different bandwidth, frequency, and return loss specifications, as well as advanced filtering functions with prescribed transmission zeros. Spurious performance of the half-cut cylinder can also be improved by cutting one or more through-way slots between opposite surfaces of the resonator. Size and mass reduction achieved by using the full and half-cut resonators described in this thesis, provide various levels of size reduction in microwave systems, both device and system level.