A four-sector switchable WiMAX antenna, for indoor use in the 4.9 -5.0 GHz frequency bands, is presented. The prototype antenna is designed to provide a higher gain in a specified sector region. Furthermore, the radiation beam is electronically steerable to provide space diversity in four different sectors. Each sector of this antenna includes an array of two rectangular microstrip patches. The air gap between the bottom substrate of microstrip patches and the ground plane is increased to 3 mm, which can aid in accomplishing a high-gain and wideband design goal. A solid-state microwave switch is used to select one of the four sectors.

The work here presents a review of beam forming architectures. As an example, the author presents an 8x8 Butler Matrix passive beam forming network including the schematic, design/modeling, operation, and simulated results. The limiting factor in traditional beam formers has been the large size dictated by transmission line based couplers. By replacing these couplers with transformer-based couplers, the matrix size is reduced substantially allowing for on chip compact integration. In the example presented, the core area, including the antenna crossover, measures 0.82mm×0.39mm (0.48% the size of a branch line coupler at the same frequency). The simulated beam forming achieves a peak PNR of 17.1 dB and 15dB from 57 to 63GHz. At the 60GHz center frequency the average insertion loss is simulated to be 3.26dB. The 8x8 Butler Matrix feeds into an 8-element antenna array to show the array patterns with single beam and adjacent beam isolation.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / In this paper, a new technique utilizing a scatterer of high dielectric constant in between electrically small antennas to achieve good Direction of arrival (DOA) estimation performance is demonstrated. The phase information of the received signal at the antennas is utilized for direction estimation. The impact of the property of the scatterer on the directional sensitivity and the output signal to noise ratio (SNR) level are studied. Finally the DOA estimation accuracy is analyzed with the proposed technique under the consumption of white Gaussian noise environment.

There has been a rapid growth of terrestrial and satellite communications in the last few decades of the 20th century. This has resulted in a heavy congestion of low microwave bands and has been a major driving force for exploring the upper microwave and millimeter-wave frequencies. One of the main requirements for a successful shift to the new frequency spectrum is the availability of high power solid-state transmitters. Solid-state devices such as diodes or transistors have been able to meet such demands when their output signals are combined using space-level power combining methods that avoid conduction losses, which become pronounced at millimeter wave frequencies. In this thesis, theoretical and experimental investigations are carried out into the spatial power combiners (SPCs) which employ active planar arrays formed by transistor amplifiers whose input and output ports are equipped with planar radiating elements. The SPC structures include the reflection-type combiner using the tile configuration of planar array and the transmission-type combiner using tile or tray configurations of planar arrays. The frequency bands chosen for the designing and testing of prototypes are X- and Ku-band. The first stage of the investigation concerns the 10 GHz reflection-type power combiner structure formed by a phased planar microstrip reflectarray (MRA) of 37-element dual-feed aperture coupled microstrip patch antennas equipped with open-circuit stubs as phasing components. The experimental tests reveal poor radiation performance and hence poor power combining efficiency of this structure. These results indicated the need for theoretical investigations into the operation of this type of SPC. The study of the unit cell of this power combiner reveals that the phase of an open-circuit stub does not increase linearly as a function of the stub length and its range is limited to less than (about is required for proper functioning). This finding, forms the basis for extending the investigations into alternative phasing mechanisms of a MRA which would offer a phasing range exceeding . A phasing mechanism exploiting variable size stacked patches is chosen. In order to accurately determine the phasing of the reflected wave, a theory based on an equivalent unit cell waveguide approach (WGA) is proposed and developed. The proposed theory is computationally efficient and is proven to be accurate compared with benchmark results published by other researchers. Following the verification, an offset feed 161-element two-layer printed MRA prototype with patches of variable size is designed and developed for operation in Ku-band. The test results aim at verifying the validity of applying a unit cell WGA to designing passive and active MRAs. The next investigations, which are presented in the thesis concern increasing operational bandwidth of the transmission-type SPC in tile configuration. The designs presented so far in the open literatures were based on edge-feed microstrip patch antennas as radiating elements of individual active stages and featured a narrow-band performance. In order to overcome this shortcoming, stacked patch (SP) microstrip antennas as receiving and transmitting elements in an active transmitarray (TXA) are proposed. For the aim of testing the proposed concept, a 16-element SP TXA is designed for operation in X-band. Two identical hard horn antennas with an approximately uniform field across the aperture for signal launching and collecting complete the design and development of this space-level power combiner. The performance of the developed device is assessed experimentally and an increased operational bandwidth is demonstrated. The final structure being investigated in the thesis project is the transmission-type SPC in tray configuration. This power combining structure employs a travelling wave antenna of uniplanar quasi-Yagi type as a radiating element to achieve broad-band operation. The investigated SPC is formed by seven trays of uniplanar quasi-Yagi antenna. In order to achieve uniform and in-phase excitation of individual trays, which is required to obtain high power combining efficiency, hard horn antennas and Schiffman phase shifters are employed in the design of this space-level combiner. The proposed device is developed and its performance is assessed through experiments. The work performed as part of this Ph.D. thesis project has resulted in 5 journal papers and 11 refereed conference papers. This acceptance rate supports the claim of the originality and significance of the research undertaken as part of the thesis project.

Dans le cadre des systèmes de positionnement par satellite GNSS (« Global Navigation Satellite Systems »), l’intégritéde la navigation d’un utilisateur est gérée en réception par la détection, l’identification voire l’exclusion de mesures depseudo-distance jugées erronées. Généralement basés sur le concept a posteriori RAIM (« Receiver Autonomous IntegrityMonitoring »), les algorithmes de contrôle autonome d’intégrité fournissent de hautes performances pour l’aviation civile,dont le contexte de navigation est caractérisé par une forte visibilité des satellites et peu de signaux parasites captéspar l’antenne réceptrice. L’algorithme WLSR RAIM est communément utilisé dans ce cadre. Néanmoins, les techniquesRAIM ne sont pas compatibles avec la navigation terrestre en milieu contraint. En effet, le contexte urbain est notammentcaractérisé par un masquage récurrent des signaux satellitaires directs ainsi que la réception de multi-trajets générés parl’environnement proche du récepteur. RAIM ne prend pas en compte l’ensemble des données disponibles en réception,dégradant ainsi fortement ses performances. Il est donc nécessaire de développer des méthodes de contrôle d’intégritécompatibles avec un tel contexte de navigation. Pour cela, la thèse propose d’étudier l’apport d’informations GNSS a priorinon utilisées par les techniques RAIM. Deux paramètres principaux ont été exploités : le signal GNSS brut reçu et lesestimations de directions d’arrivée des signaux satellitaires DOA (« Direction Of Arrival »). La première étape a consisté à implémenter une méthode a priori qui évalue la cohérence du positionnement estimé par rapport au signal brut directement reçu. Cette méthode a été nommée Direct-RAIM (D-RAIM) et a démontré une forte sensibilité de détection, permettant d’anticiper d’éventuels risques sur la navigation et de caractériser plus finement la qualité de l’environnement proche du récepteur. Toutefois, le caractère a priori de l’approche engendre de potentielles non détection d’erreurs en cas de modèle de signal défectueux. Afin de contourner cette limitation, un couplage WLSRRAIM – D-RAIM a été développé, nommé Hybrid-RAIM (H-RAIM). Une telle approche permet de combiner robustesse etsensibilité apportées par ces techniques respectives. Le second axe de recherche a mis en évidence la contribution de l’information des DOA dans un contrôle autonome d’intégrité. L’intégration d’un réseau d’antennes en réception permet d’obtenir l’estimation des DOA pour l’ensemble dela constellation visible. Théoriquement, l’évolution jointe des DOA est directement liée à l’attitude du réseau. Cet aspectpermet donc de détecter toute incohérence sur une ou plusieurs voies en cas d’estimation(s) de DOA biaisée(s), par rapportà l’ensemble de la constellation. L’algorithme RANSAC (« RANdom SAmple Consensus») a été utilisé afin de détecter toutcomportement aberrant dans l’estimation des DOA, et ainsi mesurer la confiance que l’utilisateur peut placer dans chaquevoie. L’algorithme WLSR RAIM RANSAC a ainsi été implémenté. L’intégration de la composante DOA permet d’ajouterun degré de liberté dans le contrôle autonome d’intégrité côté récepteur et ainsi d’affiner la détection voire l’exclusiond’erreurs. Au cours de cette thèse, un récepteur logiciel a été implémenté, permettant de traiter des signaux Galileo, de lagénération du signal jusqu’au positionnement puis au contrôle d’intégrité. Ce récepteur a pu être évalué à partir de donnéessimulées en environnement urbain. / In Global Navigation Satellite Systems (GNSS) applications, integrity is managed at the reception side by detection,identification and exclusion of faulty pseudorange measurements. Usually based on the a posteriori Receiver AutonomousIntegrity Monitoring (RAIM) concept, integrity techniques provide high performances for civil aviation, with a navigationcontext defined by a clear-sky environment. WLSR RAIM is commonly used. Nevertheless, RAIM techniques are notcompatible with a terrestrial navigation in harsh environments. For instance, urban areas are characterized by a poorvisibility and the reception of many multipaths derived from the receiver closed-environment. RAIM does not consider allthe available data in the reception chain, which dramatically deteriorates the detection performances. Hence, it is necessaryto develop integrity process compatible with such a navigation context. This PhD work studies the contribution of GNSSa priori information, disused by conventional RAIM techniques. Two main parameters have been exploited : the receivedraw GNSS signal and the Directions Of Arrival (DOA) estimations.This first step was devoted to the development of an a priori method which evaluates the consistence of the estimatedPosition Velocity Time (PVT) vector of the receiver with respect to the raw GNSS signal. This method has been calledDirect-RAIM (D-RAIM) and has shown high detection sensitivity, allowing the user to anticipate navigation risks and todefine precisely the quality of the receiver closed-environment. However, the a priori aspect of this approach may lead tonavigation error missed detections if the signal model is getting flawed. In order to circumvent this limitation, a WLSRRAIM – D-RAIM coupling has been developed, called Hybrid-RAIM (H-RAIM). Such an approach merges the robustnessand the sensitivity brought by both techniques.The second research step has brought to light the contribution of the DOA information in an autonomous integritymonitoring. Using an antenna array, the user can get the DOA estimations for all satellites in view. Theoretically, the DOAjoint evolution is directly correlated with the array rotation angles. Hence, any mismatch on the DOA estimations withrespect to the global constellation can be detected. RANdom Sample Consensus (RANSAC) algorithm has been used inorder to detect any faulty DOA evolution, derived from inconsistencies in reception linked to potential navigation risks :RANSAC measures the trust that the user can place in each channel. Therefore, a WLSR RAIM RANSAC algorithmhas been developed. The integration of the DOA component adds a degree of freedom in receiver autonomous integritymonitoring, refining the error detection and exclusion.Last but not least, a software receiver has been implemented processing Galileo data, from the signal generation to positioningand integrity monitoring. This software has been evaluated by simulated data characterizing urban environments.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-01-30T18:03:51Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação - Elias Marques V4.2 (Revisão Biblioteca).pdf: 4899848 bytes, checksum: 78834b022de3c1d5eb7fcee1273f65c7 (MD5) / Made available in DSpace on 2017-01-30T18:03:51Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação - Elias Marques V4.2 (Revisão Biblioteca).pdf: 4899848 bytes, checksum: 78834b022de3c1d5eb7fcee1273f65c7 (MD5) Previous issue date: 2016-02-22 / FACEPE / Este trabalho de dissertação apresenta a concepção e implantação de um sistema controlador de arranjo de antenas capaz de integrar-se a uma rede de comunicação SCADA e direcionar o diagrama de radiação de um arranjo de antenas, garantindo melhor comunicação entre estação base e remota. É apresentado um circuito de RF capaz de realizar o controle automático das fases de alimentação de um arranjo de antenas composto por diversos dispositivos de RF, incluindo um defasador de 8 bits. São apresentados testes destes dispositivos bem como a caracterização de ramos constituídos por estes componentes. Desenvolveu-se também um circuito controlador de arranjo de antenas que desempenha funções de identificação de endereços e determina as fases a serem utilizadas no controle dos defasadores. O circuito foi testado em um projeto piloto no campus da UFPE e está instalado na subestação da CELPE na cidade de Gravatá, no interior do estado de Pernambuco. / This dissertation presents the design and implementation of a Antenna Array Controller System capable of integrating into a SCADA network and directing the main radiation lobe, granting best communication between base and remote stations. An RF circuit is presented capable of automatically controlling the phases fed to the antenna array composed by several RF devices, including an 8-bit phase shifter. Tests of the devices and the characterization of braches composed by them are shown. In addition, an antenna array controller has been developed to perform functions that include the identification of an address and the determination of the phase to be used in the phase shifters’ control. The circuit was tested in a pilot project at the UFPE campus and is installed at a CELPE substation in the city of Gravatá.

The current and future demand for wireless technology is increasing rapidlyin the era of Internet-of-things, information-shower, auto-drive vehicles andthe fifth generation of mobile communications. The flourishing in wirelesstechnologies comes from their advantages such as mobility, flexibility, easy toextend, easy to install and easy to do the maintenance. However, the wirelesstechnology is suffering from many problems such as; lack of security andthe shortage of spectrum bands. The security remains a major challenge forthe wireless communications because of the broadcasting nature of wirelesssignals and massive researches have been conducted to deal with it. Beamformingis one of the physical layer security solutions that is proposed toimprove the security by focusing the majority of the transmitted power towardthe legitimate destination. The main concern about the beamformingtechnique is the relatively small amount of power that escapes from the sidelobes where any illegal user equipped with a sufficiently sensitive receivercan detect its information. The literature has been received many differentsolutions to secure the side lobes emissions. These solutions suffer from fourcommon limitations; 1) the need to modulate the signal at the antenna level,2) the data rates are restricted by the switching speed, 3) they can not easily beintegrated with the current infrastructure, and 4) they work only with phasemodulation. In this thesis, a new, simple, economic, easy to get integratedwith current phased array systems and effective solution has been proposedand analytically analysed under different circumstances, including noiseless,noisy and Rician fading channels and the effect of phase shift errors. The secondproblem addressed in this thesis is the poor spectral efficiency of spaceshift keying modulation. This thesis proposes a new physical layer directcode to improve the spectral efficiency of space shift keying modulation byexploiting the indices of both active and inactive transmitting antennas.

Broadband antenna arrays have become increasingly popular for various imaging applications, such as radio telescopes and radar, where high sensitivity and resolution are required. High sensitivity requires the development of large scale broadband arrays capable of imaging distant sources at many different wavelengths, in addition to overcoming noise and jamming signals. The design of large scale broadband antenna arrays requires large number antennas, increasing the cost and complexity of the overall system. Moreover, noise sources often vary, depending on their wavelengths and angular locations. This increases the overall design complexity particularly for broadband applications where the performance depends not only on the required bandwidth, but also on the frequency band.This thesis provides a study of broadband antenna array systems for large scale applications. The study investigates different tradeoffs associated with designing such systems and drives a novel design approach to optimize both their cost and performance for a wide range of applications. In addition, the thesis includes measurements of a suitable array to validate the computational predictions. Moreover, the thesis also demonstrates how this study can be utilized to optimize a broadband antenna array system suitable for a low frequency radio telescope.

Constant evolution requirements of Wi-Fi and cellular standards to meet the demands of better power efficiency, longer range and higher throughput of wireless networks has drawn attention to multiple antenna transmitters and receivers, i.e., multi-input multi-output(MIMO) systems. This research falls in the larger context of distributed MIMO, or DMIMO systems, wherein groups of cooperating transceivers organize themselves into virtual antenna arrays which can, in principle, emulate any MIMO technique that a centralized array can support. Beamforming and nullforming are techniques that can be employed by centralized or distributed antenna array, and can be building blocks for MIMO communication systems; these impart directionality to the array and can help cater to the demands of today's wireless networks. In beamforming, a set of distributed transmitters in a wireless network cooperatively transmit a common message signal in such a way that their individual transmissions add up to a desired SNR level at the set of designated receivers while in nullforming, cooperative transmission ensures that the individual transmissions cancel each other at the set of designated receivers. The key bottleneck in the practical realization of DMIMO is synchronization. Distributed nullforming specifically poses challenges that call for special attention. Here, we develop a set of scalable algorithms for beamforming and nullforming using distributed transmitters by forming a virtual antenna array and overcome the involved challenges in a purely distributed fashion. Under a per-antenna power constraint and assuming equal-gain channels, an ideal N-antenna beamformer provides an N squared-fold coherent power gain on target. Ideal nullforming on the other hand results in zero power on the target. These properties motivate applications in cooperative jamming or communications, where the goal is to maximize the net transmitted power using multiple transmitters while simultaneously protecting a designated receiver. For example, in a cognitive radio system where the transmit array is a secondary user of licensed spectrum which seeks to communicate with a set of secondary receivers (beam targets) without causing any interference at primary receivers (null targets). Another possible application is a cellular network where adjacent Base Stations form a transmit array and coordinate their transmissions to avoid cochannel interference. Recent algorithms on wireless security critically rely on nodes blanketing a landscape with full power jamming signals while protecting a cooperating receiver through nullforming. So a third application can be electronic warfare where a transmit array broadcasts strong jamming signals that disable an enemy's communication infrastructure while protecting friendly stations (null targets) from interference due to the jamming signal. The joint beam and nullforming specifically can be more generally thought of as a fundamental building block for increased spatial spectrum reuse and toward achieving the full spatial multiplexing gains available from MIMO techniques with distributed antenna arrays.

Full dimension (FD) multiple-input multiple-output (MIMO) technology has recently attracted substantial research attention in the 3rd Generation Partnership Project (3GPP) as a promising technique for the next-generation of wireless communication networks. FD-MIMO scenarios utilize a planar two-dimensional (2D) active antenna system (AAS) that not only allows a large number of antenna elements to be placed within feasible base station (BS) form factors, but also provides the ability of elevation beamforming. This dissertation presents the elevation beamforming analysis for cellular networks utilizing FD massive MIMO antenna arrays. In particular, two architectures are proposed for the AAS - the uniform linear array (ULA) and the uniform circular array (UCA) of antenna ports, where each port is mapped to a group of vertically arranged antenna elements with a corresponding downtilt weight vector. To support FD-MIMO techniques, this dissertation presents two different 3D ray-tracing channel modeling approaches, the ITU based ‘antenna port approach’ and the 3GPP technical report (TR) 36.873 based ‘antenna element approach’. The spatial correlation functions (SCF)s for both FD-MIMO arrays are characterized based on the antenna port approach. The resulting expressions depend on the underlying angular distributions and antenna patterns through the Fourier series coefficients of the power spectra and are therefore valid for any 3D propagation environment. Simulation results investigate the performance patterns of the two arrays as a function of several channel and array parameters. The SCF for the ULA of antenna ports is then characterized in terms of the downtilt weight vectors, based on the more recent antenna element approach. The derived SCFs are used to form the Rayleigh correlated 3D channel model. All these aspects are put together to provide a mathematical framework for the design of elevation beamforming schemes in single-cell and multi-cell scenarios. Finally, this dissertation proposes to use the double scattering channel to model limited scattering in realistic propagation environments and derives deterministic equivalents of the signal-to-interference-plus-noise ratio (SINR) and ergodic rate with regularized zeroforcing (RZF) precoding. The performance of a massive MIMO system is shown to be limited by the number of scatterers. To this end, this dissertation points out future research directions