Tatsuo Itoh : discurs llegit a la cerimònia d'investidura celebrada a la Sala d'Actes del Rectorat el dia 14 d'octubre de l'any 2015

Tatsuo Itoh va ser investit doctor honoris causa per la UAB per les seves rellevants contribucions a l'enginyeria de radiofreqüència/microones i de les telecomunicacions.Nomenament 19/03/2015. A proposta de l'Escola d'Enginyeria. L'acte d'investidura va tenir lloc el 14 d'octubre de 201

Integrated Filters and Couplers for Next Generation Wireless Tranceivers

The main focus of this thesis is to investigate the critical nonlinear distortion issues affecting RF/Microwave components such as power amplifiers (PA) and develop new and improved solutions that will improve efficiency and linearity of next generation RF/Microwave mobile wireless communication systems. This research involves evaluating the nonlinear distortions in PA for different analog and digital signals which have been a major concern. The second harmonic injection technique is explored and used to effectively suppress nonlinear distortions. This method consists of simultaneously feeding back the second harmonics at the output of the power amplifier (PA) into the input of the PA. Simulated and measured results show improved linearity results. However, for increasing frequency bandwidth, the suppression abilities reduced which is a limitation for 4G LTE and 5G networks that require larger bandwidth (above 5 MHz). This thesis explores creative ways to deal with this major drawback. The injection technique was modified with the aid of a well-designed band-stop filter. The compact narrowband notch filter designed was able to suppress nonlinear distortions very effectively when used before the PA. The notch filter is also integrated in the injection technique for LTE carrier aggregation (CA) with multiple carriers and significant improvement in nonlinear distortion performance was observed. This thesis also considers maximizing efficiency alongside with improved linearity performance. To improve on the efficiency performance of the PA, the balanced PA configuration was investigated. However, another major challenge was that the couplers used in this configuration are very large in size at the desired operating frequency. In this thesis, this problem was solved by designing a compact branch line coupler. The novel coupler was simulated, fabricated and measured with performance comparable to its conventional equivalent and the coupler achieved substantial size reduction over others. The coupler is implemented in the balanced PA configuration giving improved input and output matching abilities. The proposed balanced PA is also implemented in 4G LTE and 5G wireless transmitters. This thesis provides simulation and measured results for all balanced PA cases with substantial efficiency and linearity improvements observed even for higher bandwidths (above 5 MHz). Additionally, the coupler is successfully integrated with rectifiers for improved energy harvesting performance and gave improved RF-dc conversion efficienc

Amplificador Doherty e antena combinadora

The conventional Doherty architecture is commonly used in wireless transmitters for its ability to boost the average efficiency of a traditional single-ended class B amplifier. It consists of two parallel single-ended amplifying branches (named carrier and peaking amplifiers) which are linked, at the output, through a /4 combiner. This output combiner commonly has a significant impact on the overall bandwidth, as it is usually built from a transmission line structure with tuned dimensions. Other non-conventional combining structures could be designed, targeting a wider bandwidth, contributing to an overall increase of the Doherty amplifier’s bandwidth. Being this an high relevance research topic for the development of high efficient and broadband amplifiers, it is highly desirable to have a laboratory setup that implements a Doherty power amplifier to which distinct output combiner structures can be connected and tested. In that sense, the design of two single-ended amplifiers (the carrier and the peaking) was performed in a circuit simulator (ADS, from Keysight) together with the input power divider that compose the Doherty architecture. The Doherty amplifier main board was designed to incorporate the carrier and peaking amplifiers, and also the power splitter at the input, and it was prepared so that it could be connected to any desired combiner to be tested. A traditional Doherty power combiner was designed and both boards (Doherty amplifier and the combiner) were produced, connected and tested in the RF laboratory. The measured amplifier presented the typical caractheristics of a Doherty amplifier with nearly 75% of drain efficiency at full-power, and nearly 50% at the output back-off level. In addition, a second combiner unit was designed with two purposes. The first was to demonstrate the operation of the designed Doherty amplifier with a distinct output combiner, showing that, as intended in this work, it is suited to test multiple combiner structures. The second objective was to serve as preliminary test to evaluate the possibility of merging the output combiner with the antenna element. Taking advantage of the electromagnetic coupling between antennas, this second combiner structure uses two antenna elements that were tuned to simultaneously behave as output combiner of the Doherty amplifier and a radiating element.A arquitetura Doherty convencional é tipicamente utilizada em transmissores sem fios pela sua capacidade de aumentar a eficiência média de um tradicional amplificador em classe B. O amplificador Doherty consiste em dois amplificadores em paralelo (chamados de amplificadores carrier e peaking) que são ligados, na saída, através de um combinador de /4. Este combinador de saída geralmente tem um impacto significativo na largura de banda do amplificador, pois é tipicamente construído a partir de uma estrutura de linhas de transmissão com dimensões ajustadas para uma frequência. Outras estruturas de combinadores não convencionais podem ser projetadas, visando uma largura de banda maior, contribuindo para um aumento geral da largura de banda do amplificador Doherty. Sendo este um tópico de investigação de elevada relevância para o desenvolvimento de amplificadores de alta eficiência e largura de banda, seria interessante ter um setup de laboratório que implemente um amplificador de potência Doherty para o qual estruturas combinadoras distintas possam ser ligadas à saída do amplificador e testadas. Nesse sentido, o projeto de dois amplificadores (carrier e peaking) foi realizado num simulador de circuitos (ADS, da Keysight) junto com o divisor de potência de entrada que compõe a arquitetura Doherty. A placa principal do amplificador Doherty foi projetada para incorporar os amplificadores carrier e peaking, e também o divisor de potência na entrada, e foi preparada de modo que pudesse ser ligada a qualquer combinador desejado a ser testado. Um combinador de potência Doherty tradicional foi projetado e ambas as placas (amplificador Doherty e o combinador) foram produzidas, soldadas e testadas no laboratório de RF. O amplificador medido apresentou as características típicas de um amplificador Doherty com aproximadamente 75% de eficiência de dreno na potência máxima e aproximadamente 50% no ponto de output back-off. Além disso, foi projetado um segundo combinador com dois objetivos. O primeiro foi demonstrar o funcionamento do amplificador Doherty projetado com um combinador de saída distinto, mostrando que, como pretendido neste trabalho, o amplificador desenhado é adequado para testar múltiplas estruturas combinadoras. O segundo objetivo foi servir como teste preliminar para avaliar a possibilidade de fundir o combinador de saída com a antena. Aproveitando o acoplamento eletromagnético entre antenas, esta segunda estrutura combinadora utiliza duas antenas que foram projetadas para se comportarem simultaneamente como combinador de saída do amplificador Doherty e como elemento radiante.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Design and analysis of wideband passive microwave devices using planar structures

A selected volume of work consisting of 84 published journal papers is presented to demonstrate the contributions made by the author in the last seven years of his work at the University of Queensland in the area of Microwave Engineering. The over-arching theme in the author’s works included in this volume is the engineering of novel passive microwave devices that are key components in the building of any microwave system. The author’s contribution covers innovative designs, design methods and analyses for the following key devices and associated systems: Wideband antennas and associated systems Band-notched and multiband antennas Directional couplers and associated systems Power dividers and associated systems Microwave filters Phase shifters Much of the motivation for the work arose from the desire to contribute to the engineering o

Quantum Barrier Devices for Sub-Millimetre Wave Detection

Resonant-Tunnelling Diodes (RTDs) are a specific class of Quantum Barrier Devices, which offer a lot of potential for customisation through careful engineering of their semiconductor layer structure. They exhibit characteristics that make them good candidates for use in both subharmonic mixers and signal amplifiers, that operate at millimetre and sub-millimetre frequencies. In this thesis RTDs fabricated at the University of Leeds from three different layer structures are investigated. Initially, device measurements are presented along with a device model for use in circuit simulation software. Planar transmission media circuits were designed for subharmonic mixers and two types of amplifiers, all using these devices. Additional circuits, implemented in waveguide technology, were also studied in preparation for realising the RTD based amplifiers at sub-millimetre and terahertz frequencies. The sub-harmonic mixer circuits were simulated at microwave, millimetre, and sub-millimetre frequencies. Best predicted conversion loss performance is on the order of 20 dB. It was found that amongst the devices used an optimum size exists, offering best trade-off between junction capacitance and current density. The amplifier circuits are divided into two groups, reflection based amplifiers and active transmission line. Their purpose would be to complement the mixers towards eventually building a receiver with low power requirements and low overall conversion loss. The former were found to either exhibit high narrow-band gain, while the latter had low wide-band gain, with an additional, resonant peak at frequencies in the sub-millimetre wave region. The project was primarily a parametric design study, rather than a build and test project. Therefore, the simulation results are used to determine what characteristics of the devices studied would make them suited for use in circuits at high frequencies; and to come up with recommendations for future optimum RTD layer design

Low Temperature Co-fired Ceramics for System-in-Package Applications at 122 GHz

This work presents a low temperature co-fired ceramic (LTCC) technology based system-in-package (SiP) operating beyond 100 GHz. The SiP encloses a semiconductor transceiver chip in a pea-sized LTCC package. The SiP is efficient and robust in terms of its electrical, thermal and mechanical characteristics. Moreover, it is low-cost and requires only standard manufacturing and assembly techniques. Finally, two fully-integrated 122 GHz radar sensors are demonstrated in LTCC technology