Dissertations / Theses on the topic 'Uda-yagi'

This work deals with the study of Yagi-Uda antennas, followed by analysis and design of planar antenna with wired reflector. The first part focused on the analysis of the antenna and parameters. Another part of the continuing investigation of the optimum parameters for a given antenna followed by a design in Wi-Fi 5 GHz band. The antenna is simulated in CST Microwave Studio. The final part devoted the results achieved

El ser humano desde siempre ha tenido la necesidad innata de comunicarse en cualquier lugar y en cualquier momento. Esto ha impulsado un desarrollo asombroso en el área de las telecomunicaciones y especialmente en los últimos 30 años, en los cuales se han logrado tales avances en esta área de la ingeniería que a esta etapa de la historia de la humanidad se le ha denominado como la “era de las comunicaciones”. Hace más de un siglo que Hertz demostró la posibilidad de enviar ondas electromagnéticas de un punto al otro vía inalámbrica. Menos de una década después, Marconi puso en marcha la primera comunicación transatlántica dando origen al negocio de las telecomunicaciones [1]. En los últimos treinta años, gracias al avance de los computadores y al perfeccionamiento de las técnicas numéricas se han producido mejoras significativas en los parámetros de desempeño de las antenas, debido a que se han podido implementar dichos métodos para estructuras muy complejas. En la actualidad existen diversos programas de análisis de antenas basados en estos métodos, los cuales han contribuido al avance de las telecomunicaciones [1]. En el presente trabajo de investigación se expone los fundamentos electromagnéticos aplicados a antenas y su implementación computacional; posteriormente se explicara los fundamentos teóricos de optimización teniendo como técnica principal a los algoritmos genéticos. A partir de esto se propone un diseño para la solución óptima de desempeño para antenas Yagi. El desarrollo del diseño del sistema de optimización se expone en 4 capítulos. En el primero, se aborda la teoría de antenas; en el segundo, se expone a los algoritmos genéticos; en el tercero, se explica el diseño de optimización y sus restricciones; finalmente, en el cuarto, se realizan las pruebas de simulación para demostrar el funcionamiento adecuado y esperado.
Tesis

The baluns are the key components in balanced circuits such balanced mixers, frequency multipliers, push–pull amplifiers, and antennas. Most of these applications have become more integrated which demands the baluns to be in compact size and low cost. In this thesis, a new approach about the design of planar balun is presented where the 4-port symmetrical network with one port terminated by open circuit is first analyzed by using even- and odd-mode excitations. With full design equations, the proposed balun presents perfect balanced output and good input matching and the measurement results make a good agreement with the simulations. Second, Yagi-Uda antenna is also introduced as an entry to fully understand the quasi-Yagi antenna. Both of the antennas have the same design requirements and present the radiation properties. The arrangement of the antenna’s elements and the end-fire radiation property of the antenna have been presented. Finally, the quasi-Yagi antenna is used as an application of the balun where the proposed balun is employed to feed a quasi-Yagi antenna. The antenna is working in the S-band radio frequency and achieves a measured 36% fractional bandwidth for return loss less than -10 dB. The antenna demonstrates a good agreement between its measurement and simulation results. The impact of the parasitic director on the antenna’s performance is also investigated. The gain and the frequency range of the antenna have been reduced due to the absence of this element. This reduction presents in simulation and measurement results with very close agreement.

The purpose of this research is to find ways to create an omnidirectional antenna with high directivity in the vertical plane. The investigation is based on computer simulation using the program CST 2011. The objective is a narrow-band antenna that is omnidirectional in the horizontal plane and has maximum achievable directivity for a fixed size. Three of the most promising antenna designs are selected based on the current state of antenna technology. Their maximum directivities are estimated by means of well known relations in antenna theory. It is shown that the most suitable design is an omnidirectional antenna in the form of a cylindrical dipole antenna array with an active central dipole. For this antenna, excitation by means of a radial traveling wave, with a phase velocity smaller than speed of the light, is possible. It is found that for a certain value of a moderating factor it is possible to obtain a directivity that is 2.5 – 3 dB larger than that of a dipole or a linear antenna with uniform excitation. The antenna structures are modeled to determine the number of dipoles, their dimensions and the spacing between them that maximizes the directivity.

Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2019
This dissertation presents a concept for a compact, low-profile, integrated solar panel antenna for use on small satellites in low Earth orbit. To date, the integrated solar panel antenna design approach has primarily been, patch (transparent or non-transparent) and slot radiators. The design approach presented here is proposed as an alternative to existing designs. A prototype, comprising of an optically transparent rectangular dielectric resonator was constructed and can be mounted on top of a solar panel of a Cube Satellite. The ceramic glass, LASF35 is characterised by its excellent transmittance and was used to realise an antenna which does not compete with solar panels for surface area. Currently, no closed-form solution for the resonant frequency and Q-factor of a rectangular dielectric resonator antenna exists and as a first-order solution the dielectric waveguide model was used to derive the geometrical dimensions of the dielectric resonator antenna. The result obtained with the dielectric waveguide model is compared with several numerical methods such as the method of moments, finite integration technique, radar cross-section technique, characteristic mode analysis and finally with measurements. This verification approach was taken to give insight into the resonant modes and modal behaviour of the antenna. The interaction between antenna and a triple-junction gallium arsenide solar cell is presented demonstrating a loss in solar efficiency of 15.3%. A single rectangular dielectric resonator antenna mounted on a ground plane demonstrated a gain of 4.2 dBi and 5.7 dBi with and without the solar cell respectively. A dielectric resonator antenna array with a back-to-back Yagi-Uda topology is proposed, designed and evaluated. The main beam of this array can be steered can steer its beam ensuring a constant flux density at a satellite ground station. This isoflux gain profile is formed by the envelope of the steered beams which are controlled using a single digital phase shifter. The array achieved a beam-steering limit of ±66° with a measured maximum gain of 11.4 dBi. The outcome of this research is to realise a single component with dual functionality satisfying the cost, size and weight requirements of small satellites by optimally utilising the surface area of the solar panels.

El control dinámico y determinístico de la luz en una escala espacial por debajo de la longitud de onda es un requisito clave para ampliar los conceptos y las funcionalidades de la macro-óptica hasta la escala nanométrica. Un mayor nivel de control también tendrá implicaciones importantes en nuestra comprensión de los fenómenos ópticos en la nanoescala. Uno de los principales problemas en nano-óptica tiene como objetivo describir cómo y con qué precisión es posible controlar la distribución espacial de la luz de forma dinámica en la nanoescala. Desafortunadamente, un límite fundamental de la física – el límite de difracción de la luz – afecta nuestra capacidad de seleccionar ópticamente puntos separados por menos de media longitud de onda de la luz. El campo de la plasmónica ofrece una oportunidad única para cerrar la brecha entre el límite de difracción y la escala nanométrica. Nanoantenas metálicas pueden acoplarse eficientemente a luz propagante y focalizarla en volúmenes nanométricos, y viceversa. Además, estas nanoantenas prometen mejorar significativamente la eficiencia de procesos como le fotodetección, la emisión de luz, sensores, transferencia de calor, y espectroscopía a la escala nanométrica. Aprender a controlar de forma precisa la respuesta óptica de estas nanoantenas representa un enfoque muy prometedor para controlar la distribución espacial y temporal de la luz a la escala nanométrica. Tradicionalmente, se han desarrollado dos principales estrategias para el control de la respuesta óptica de nanoantenas plasmónicas: la primer estrategia (estrategia estática) tiene como objetivo la optimización del diseño geométrico de las nanoantenas acorde a su aplicación, mientras que la segunda estrategia (estrategia dinámica) tiene como objetivo la modulación reversible del campo cercano de una nanoestructura dada a través de la manipulación de la luz de excitación en el tiempo y el espacio. El trabajo presentado en esta Tesis extiende el estado del arte de estas dos estrategias, y desarrolla nuevas herramientas, tanto experimentales como teóricas, para ampliar el nivel de control que tenemos sobre la distribución espacial de la luz debajo del límite de difracción. Después de presentar una visión general de los principios básicos de nano-óptica y de la óptica de lo plasmones de superficie, el Capítulo 1 repasa los avances en el control de la respuesta óptica de nanoestructuras metálicas – sea por una estrategia estática o dinámica – en el momento en que se inició este trabajo de investigación. La modificación de la geometría y las dimensiones de las nanpartículas metálicas sigue siendo un ingrediente fundamental para controlar las resonancias plasmónicas y los campos de luz a la escala nanométrica. Como ejemplos novedosos de control estático, por lo tanto, los Capítulos 2 y 3 estudian nuevos diseños de estructuras plasmónicas con capacidades sin precedentes de modelar campos de luz a la escala nanométrica, en particular un diseño fractal y una nanoantena unidireccional tipo Yagi-Uda. Los Capítuols 4 y 5 describen una nueva herramienta teórica y experimental para el control dinámico y determinístico de la respuesta óptica de nanoantenas basada en la modulación espacial de la fase de la luz de excitación: el campo óptico cercano, que resulta de la interacción entre la luz y las nanoestructuras plasmónicas, es normalmente determinado por la geometría del sistema metálico y las propiedades de la luz incidente, como su longitud de onda y su polarización; sin embargo, el control exacto y dinámico del campo óptico cercano debajo de límite de difracción de la luz – independientemente de la geometría de la nanoestructura – es también un ingrediente importante para el desarrollo de futuros dispositivos nano-ópticos y para ampliar los conceptos y las funcionalidades de la óptica macroscópica a la escala nanométrica. Finalmente, la Conclusión resume los resultados de este trabajo y ofrece una visión general de algunos estudios paralelos a esta tesis. Algunas de las observaciones finales permiten echar un vistazo a las perspectivas y estrategias futuras para complementar el control estático y el control dinámico en una única herramienta, que podría avanzar enormemente nuestra capacidad de controlar la respuesta óptica de nanoantennas debajo del límite de difracción.
El control dinámico y determinístico de la luz en una escala espacial por debajo de la longitud de onda es un requisito clave para ampliar los conceptos y las funcionalidades de la macro-óptica hasta la escala nanométrica. Un mayor nivel de control también tendrá implicaciones importantes en nuestra comprensión de los fenómenos ópticos en la nanoescala. Uno de los principales problemas en nano-óptica tiene como objetivo describir cómo y con qué precisión es posible controlar la distribución espacial de la luz de forma dinámica en la nanoescala. Desafortunadamente, un límite fundamental de la física – el límite de difracción de la luz – afecta nuestra capacidad de seleccionar ópticamente puntos separados por menos de media longitud de onda de la luz. El campo de la plasmónica ofrece una oportunidad única para cerrar la brecha entre el límite de difracción y la escala nanométrica. Nanoantenas metálicas pueden acoplarse eficientemente a luz propagante y focalizarla en volúmenes nanométricos, y viceversa. Además, estas nanoantenas prometen mejorar significativamente la eficiencia de procesos como le fotodetección, la emisión de luz, sensores, transferencia de calor, y espectroscopía a la escala nanométrica. Aprender a controlar de forma precisa la respuesta óptica de estas nanoantenas representa un enfoque muy prometedor para controlar la distribución espacial y temporal de la luz a la escala nanométrica. Tradicionalmente, se han desarrollado dos principales estrategias para el control de la respuesta óptica de nanoantenas plasmónicas: la primer estrategia (estrategia estática) tiene como objetivo la optimización del diseño geométrico de las nanoantenas acorde a su aplicación, mientras que la segunda estrategia (estrategia dinámica) tiene como objetivo la modulación reversible del campo cercano de una nanoestructura dada a través de la manipulación de la luz de excitación en el tiempo y el espacio. El trabajo presentado en esta Tesis extiende el estado del arte de estas dos estrategias, y desarrolla nuevas herramientas, tanto experimentales como teóricas, para ampliar el nivel de control que tenemos sobre la distribución espacial de la luz debajo del límite de difracción. Después de presentar una visión general de los principios básicos de nano-óptica y de la óptica de lo plasmones de superficie, el Capítulo 1 repasa los avances en el control de la respuesta óptica de nanoestructuras metálicas – sea por una estrategia estática o dinámica – en el momento en que se inició este trabajo de investigación. La modificación de la geometría y las dimensiones de las nanpartículas metálicas sigue siendo un ingrediente fundamental para controlar las resonancias plasmónicas y los campos de luz a la escala nanométrica. Como ejemplos novedosos de control estático, por lo tanto, los Capítulos 2 y 3 estudian nuevos diseños de estructuras plasmónicas con capacidades sin precedentes de modelar campos de luz a la escala nanométrica, en particular un diseño fractal y una nanoantena unidireccional tipo Yagi-Uda. Los Capítuols 4 y 5 describen una nueva herramienta teórica y experimental para el control dinámico y determinístico de la respuesta óptica de nanoantenas basada en la modulación espacial de la fase de la luz de excitación: el campo óptico cercano, que resulta de la interacción entre la luz y las nanoestructuras plasmónicas, es normalmente determinado por la geometría del sistema metálico y las propiedades de la luz incidente, como su longitud de onda y su polarización; sin embargo, el control exacto y dinámico del campo óptico cercano debajo de límite de difracción de la luz – independientemente de la geometría de la nanoestructura – es también un ingrediente importante para el desarrollo de futuros dispositivos nano-ópticos y para ampliar los conceptos y las funcionalidades de la óptica macroscópica a la escala nanométrica. Finalmente, la Conclusión resume los resultados de este trabajo y ofrece una visión general de algunos estudios paralelos a esta tesis. Algunas de las observaciones finales permiten echar un vistazo a las perspectivas y estrategias futuras para complementar el control estático y el control dinámico en una única herramienta, que podría avanzar enormemente nuestra capacidad de controlar la respuesta óptica de nanoantennas debajo del límite de difracción.

This thesis is focused on the design of the antenna to a specific application XY. Emphasis is placed on a narrow antenna beam width, which will ensure full-fledged profit for the tag directly below the antenna. This thesis presents a total of five proposals that could be used by XY application. This thesis also presents the results of field measurements, which confirm the improved characteristics of the antenna with parasitic patch.

In this thesis, design and realization of a system which enables precise positioning of RFID tags in both azimuth and elevation angles is explained. The positioning is based on measuring the phase difference between four Yagi antennas placed in two arrays. One array is placed in the azimuth plane and the other array is perpendicular to the first array in the elevation plane. The phase difference of the signals received from the antennas in the azimuth array is used to find the position of RFID tag in the horizontal direction. For the position in the vertical direction, the phase difference of the signals received from the antennas in the elevation plane is used. After that the position of tag in horizontal and vertical directions is used to control the mouse cursor in the horizontal and vertical directions on the computer screen. In this way by attaching one RFID tag to a plastic rod, a wireless pen is implemented which enables drawing in the air by using a program like Paint in Windows. Simulated results show that the resolution of the tag positioning in the system is in the order of 3mm in a distance equal to 0.5 meter in front of the array with few number of averaging over the received phase data. Using the system in practice reveals that it is easily possible to write and draw with this RFID pen. In addition it is argued how the system is totally immune to any counterfeit attempt for faked drawings by randomly changing the transmitting antenna in the array. This will make the system a novel option for human identity verification.

QC 20100920

Control theory of complex systems by utilization of artificial intelligent algorithms is relatively new science field and it can be used in many areas of technical practise. Best known algorithms to solved similar tasks are genetic algorithm, differential evolution, HC12 Nelder-Mead method, fuzzy logic and grammatical evolution. Complex solution is presented at selected examples from mathematical nonlinear systems to examples of anthems design and stabilization of deterministic chaos. The goal of this thesis is present examples of implementation and utilization of artificial algorithms by multi-objective optimization. To achieve optimal results is used designed software solution by multi-platform application, which used Matlab and Java interfaces. The software solution integrate every algorithms of this thesis to complex solution and it extends possible application of those approaches to real systems and practical world.

碩士
國立中正大學
通訊工程學系
98
In this thesis, two types of planar microstrip Yagi-Uda antenna fabricated on a FR4 substrate are investigated. The design is based on the planar half wavelngth dipole antenna with directing elements to form the high gain antenna. The first planar microstrip Yagi-Uda antenna was designed at 2.4 GHz for IEEE 802.11 b/g/n WLAN which has the return loss of 13.3 dB and antenna gain of 9.36 dBi and the bandwidth of 500 MHz. The second Yagi-Uda antenna has the bandwidth extention for IEEE 802.11 b/g/n WLAN, IEEE802.16 WiMAX , and 3GPP LTE applications, there measured return loss is 16 dB in 2.3-2.7 GHz and antenna gain is 8.99 dBi at 2.5GHz. The experimental results show good agreement with the simulated data.

碩士
國立臺北科技大學
電腦與通訊研究所
100
Thesis Title: Yagi-Uda Antenna for DTV Signal Receptions Pages：108 School: National Taipei University of Technology Institute: Institute of Computer and Communication Engineering Date: July 2012 Degree: Master Graduate Student: Yao-Ting Wang Advisor: Cheng-Chieh Yu, Provost, Prof., Ph.D. Keywords: DVB-T, Yagi-Uda Antenna, Dipole Antenna, UHF Band This paper presents a digital antenna, and designed to meet the global digital television broadcast receiver (470MHz ~ 860MHz) Yagi antenna. FR4 printed circuit board, the antenna design, low cost, and high gain Yagi antenna characteristics to regulate draw the antenna covers the digital TV signals, to add compared to other low-noise amplifiers LNAs (Low Noise Amplifier) enhance the strength of signal power antenna, the reception of the antenna is pretty good. The focus of this antenna for omni-directional Yagi antenna, the paper feed toward the application before the can to achieve the advantages of receiving no dead ends. We first present a printed Yagi antenna designed for digital TV signals, the size of 30 × 20 × 1.6cm3 covered by a frequency of 561MHz ~ 725MHz. The second proposed bending Yagi antenna, its size is 15 x 15 x 1.6 cm3 covered by the 420 ~ 946MHz frequency, compared to the original antenna, the antenna smaller, but wider bandwidth. Secondly, to explore the problem of low and high frequency of the antenna area, and to identify the main cause of low and high frequency, followed by digital TV receiver in a different place to test, Taiwan received channel for 16 channels.

碩士
臺北城市科技大學
資訊應用產業碩士專班
103
Yagi-Uda antenna is a typical directional antenna, from national defense, down to the common people, it is widely used in radar, communication and other radio technical equipment. If you want to improve radiation response and characteristics of the antenna, you can properly adjust the element (or rod) length and the distance between element and element. But Yagi-Uda antenna’s design have some disadvantages, such as narrow bandwidth, anti-interference performance is relatively poor. And Yagi-Uda antenna only can achieve end-fire radiation, it is not able to directly with the carrier surface by coplanar installation. If you are using microstrip patch design to approach the Yagi-Uda antenna, it can achieve small size, thin profile, and it is convenient to integrate with active components (integrated circuit) in a single printed circuit board each other. The main purpose of this paper is the design and analysis of microstrip Yagi-Uda antenna frequency at 2.45GHz single band and 2.45GHz/5.8GHz daul-band. By Ansoft HFSS software for Yagi-Uda antenna structural design and performance analysis, and further propose design improvement and optimization methods. This paper is characterized by microstrip design, Yagi-Uda antenna size is miniaturization, In frequency 2.45GHz single band and 2.45 / 5.8GHz dual-band antenna design, both antennas are designed with the same size 70x70x1.6mm (LxWxH) of FR-4 printed circuit board separately. For 2.45GHz single band antenna, its bandwidth is 550MHz, and bandwidth percentage is 22.4%. For 2.45 / 5.8GHz dual-band antenna, its bandwidth are 500MHz and 1.35GHz, and bandwidth percentages are 20.4% and 23.2% respectively.

碩士
元智大學
通訊工程學系
104
At 1953 PCB design of strip line and PCB type antenna was start and application. This type will be reduce antenna cost and design spacing of antenna, and RF signal use strip line director transmission to antenna very simple and easy to maching antenna and strip line between, not need another coaxial cable and connector, will be reduce signal loss by coaxial cable and miss matching of the connector. Result will be down cost and process sequence without PCB. Radio frequency communications for 5G generations antenna design will be studying, when data transmission with bandwidth require will be increasing and growing, radio frequency communications need up to millimeter wave is future trend,antenna size and spacing reduce will design by millimeter wave.Antenna type design of Yagi-Uda, it have good design easy to high gain, directivity and bandwidth property. For future antenna design make antenna array and link phase shift IC, than control pahse direction, RF power, Gain…e.t.c. application. point to point or one to many data transmission is good idea.

碩士
樹德科技大學
電腦與通訊系碩士班
102
This study proposed an enhanced Yagi-Uda antenna that was compatible with GPS and WLAN. The antenna had two designs, showing omnidirectional and directional radiation patterns respectively. Moreover, this study examined the influence of the addition of a directional device on the radiation pattern and introduced three highly directional antenna designs.The first antennal system design adopted a symmetric trapezoid as the dipole antenna unit. By placing reflective metal ground plane of the same form at a certain spacing, an antenna system that was operated on the WLAN frequency band and demonstrated good radiation gain was established. The second antenna design was an enhanced version of the first design, whose antenna was originally separated. A part of the main antenna ground plane was connected to the reflective metal to create a new low-frequency mode while preserving the original mode that was operated on the WLAN band. The created mode was operated on the GPS band and the antenna could enable the dual radiation patterns of omnidirectivity and directivity. The third antenna design was an extension of the second design by adding a directional device to the original architecture in order to increase the radiation gain of the antenna. This design effectively enhanced the gain of the directional radiation pattern and did not compromise the properties of the dual radiation pattern. The directional radiation pattern experienced increased gain of 1 dBi. Moreover, the antenna design was compatible with both GPS and WLAN environments.

碩士
國立臺灣大學
電信工程學研究所
98
Yagi-Uda is one of the most popular antennas for all applications. It usually has three parts, including a radiator, several directors and several reflectors. Yagi-Uda antenna can be easily designed and achieve relatively high gain. For example, a properly designed three-element Yagi-Uda antenna can achieve gain of about 7~8dB. Therefore, Yagi-Uda is good for use in point-to-point wireless communication. In this thesis, we proposed a new structure that is a stacking Yagi-Uda antenna in LTCC substrate and operating in V-band. Five different types of Yagi-Uda antenna for different radiation directions are presented. Also transmitting and receiving modules integrated with embedded stacked Yagi-Uda antenna and flip-chip dies are also shown. Design procedures, simulation results and measurement results for all designs are given. The measured typical gain of antenna for vertical radiation is about 4~5dB.

碩士
國立臺灣海洋大學
電機工程學系
102
In this thesis, two types of array antennas fabricated on a FR4 substrate are investigated.The main objective of this study is to discuss and implement PTP (Point-to-Point) array antennas applied to fixed outdoor CPE (Customer Premises Equipment) of WiMAX Wireless Communication System. The first microstrip antenna was designed at 2.6 GHz The main studies include simulation and discussion of different kinds of planar array antennas, design, simulation and practical measurement of 1 x 4, 1 x 6 planar microstrip array antennas. The measurement results are shown that: the 1 x 4 array has 110 MHz impedance bandwidth, the return loss of -25 dB ,the gain is 6.5 dB,; the 1 x 6 array has 110 MHz impedance bandwidth , the return loss of -50 dB ,the gain is 8.9 dB. The second antenna is based on the planar half wavelngth dipole antenna with directing elements to form the high gain antenna. The planar microstrip Yagi-Uda antenna was designed at 2.6 GHz for WiMAX which has the return loss of -35 dB and antenna gain of 8.7 dB and the bandwidth of 500 MHz. both forms with a high gain. The first antenna with high directivity, the latter has a wider bandwidth, both can be used in the 2.6G band of WiMAX,the experimental results show good agreement with the simulated data.

碩士
義守大學
電機工程學系
104
In this thesis, in the 2.4 GHz band of Wireless power transmission system, the case in recent years was due to rising mobile phone usage and universality, WLAN Wi-Fi Internet are becoming more common, the relative power consumption of the phone is very fast but do not want action to bring the case plus power supply, in view of the proposed concept to WLAN Wi-Fi as charging energy. The wireless power transmission system research can be divided into two parts, the first part of the antenna receiving portion, the second part is the rectified voltage output section, so the text in two parts as the research directions were modified eight element Yagi antenna, its major adjustments eight modules Yagi the lead unit and the length of the pitch to improve the polarization direction becomes higher gain antenna to increase the width of the excitation unit and antenna bandwidth can more comfortably through the next network analyzer can measure the reflection coefficient obtaining 2.45GHz - 40dB, impedance is about 52-j0.1Ω. The second part is to improve rectifier output end portion of the output voltage, picking two or three times doubler circuit ,if directly connected in series to at 14dBm signal generator, the voltage doubler circuit which outputs up to 11 V , and in under the same conditions, through the lower reception antenna radiation and antenna and voltage doubler actual measurement does not match up to the DC output of 5.2 volts.

碩士
國立臺灣大學
電信工程學研究所
105
The finite-difference time-domain method (FDTD) has been widely used in computational electromagnetics. We developed a parallelized three-dimensional (3-D) FDTD simulator in C++ language. The message passing interface (MPI) protocol is applied to our simulator for parallelizing several computers in the computation in order to speed up the process and shorten the simulation time. In this research, the main topic is to analyze the far-field properties of metallic and all-dielectric nano-antennas, and we focus on Yagi-Uda type structures. Due to low loss, the all-dielectric nano-antennas have earned much attention recently. Yagi-Uda antennas possess high directivity, however the large size of their structure is a major drawback. Yagi-Uda nano-antennas have relatively small size, thus it can avoid the size drawback. In this research, the wave source is a broadband single emitter. We analyze nano-antennas and discuss the difference between all-dielectric and metallic structures. Considering practical applications, we also study the Yagi-Uda nano-antennas on substrate. On the other hand, the Cylindrical-Rod Yagi-Uda nano-antennas are also investigated in this thesis.

In this dissertation three Yagi-Uda antennas were built, one with a frequency of operation of 2.4 GHz and the others operating at 24 GHz. Yagi-Uda antennas are well known, but here, printed Yagi-like prototypes were developed since nowadays most systems require printed circuits. Moreover, a comparison on the performance of a planar and a multilayer Yagi antenna was made, both operating in the mmWave region. Throughout the work it was possible to progressively improve gain and bandwidth, starting in the 2.4 GHz antenna and culminating in the multilayer prototype. These results were achieved without damage of the antennas’ global efficiency, which was kept at quite satisfactory values.
Nesta dissertação foram construídas três antenas Yagi-Uda, uma delas cuja frequência de operação é 2.4 GHz, enquanto as restantes operam a 24 GHz. As antenas Yagi-Uda são bastante conhecidas, no entanto, aqui, foram desenvolvidos protótipos impressos de antenas Yagi, já que, hoje em dia a maioria dos sistemas requer circuitos impressos. Mais ainda, foi feita uma comparação entre a performance de uma antena planar e a de uma antena multicamada, ambas a operar na região das ondas milimétricas. No decorrer do trabalho foi possível melhorar progressivamente tanto o ganho como a largura de banda das antenas, começando no protótipo de 2.4 GHz e culminando na estrutura multicamada. Estes resultados foram obtidos sem prejudicar a eficiência global das antenas, estando estes sempre em valores bastante razoáveis.
Mestrado em Engenharia Eletrónica e Telecomunicações

碩士
國立清華大學
化學系
104
Inspired by radio-frequency antenna technology, engineering of plasmonic nanoantenna has gain considerable interests in recent years since it provides the opportunities to manipulate the interaction of high-frequency electromagnetic (EM) wave and matter at nanoscale. In this thesis, we present two topic regarding to the control of light and matter interaction using plasmonic nanoantennas. In the first topic, we present a new design of two dimensional grating with continuous azimuthal angle-dependent periodicity for broadband surface plasmon wave excitation. The Plasmonic Doppler Grating (PDG) consists of a set of non-concentric circular rings that mimics the wavefronts of a moving point source and, therefore, presents azimuthal angle-resolved grating periodicity. The center and span of the working frequency window are fully designable for optimal performance in specific applications. We detail the design, fabrication and optical characterization of the PDG and demonstrate its exemplary applications in azimuthal angle-resolved color sorting, index sensing and surface-enhanced Raman scattering (SERS). We show that broadband source can be sorted continuously into surface plasmons and the variation in surrounding index can be reported as the change of in-plane angle distribution of color. Applications of PDG in grating couplers for silicon photonic circuits, hydrogen sensing, surface plasmon-enhanced spectroscopy and non-linear signal generation are anticipated. In the second topic, we investigate the driving of directional optical nanoantennas via continuum photoluminescence emission from the gold nanostructures upon laser excitation. By employing photoluminescence (PL) spectroscopy and back-focal plane imaging technique, we study the PL emission wavelength and directivity of four different type gold nanoantennas, which is nanorods, Yagi-Uda (YU) nanoantenna, L-shape Yagi-Uda nanoantenna and log-periodic dipole nanoantenna. We show that the PL emission band always match with the operating wavelength of nanoantennas upon modulation of localized surface plasmon resonance modes, therefore rendering the driving of nanoantenna practical. For example, we shows that three different Yagi-Uda nanoantennas can launch the PL with 650 nm, 800 nm and 850 nm wavelength respectively to a single direction without placing any external quantum emitter near the feed element. Consequently, the PL emission also allow us to experimentally investigate the directivity of broadband log-periodic dipole nanoantenna for the first time. In comparison with the radio-frequency antennas, our results show that the element of optical nanoantennas not only can act as a resonator but also can be a local broadband light source. The PL of gold nanoantennas is an ideal nanoscale unidirectional light source that can be applied in wide field such as high-bandwidth wireless optical communication.

A evolução tecnológica leva ao aparecimento de novos meios e novas realidades, revolucionando por completo o mundo. O Exército Português também acompanha esta evolução e adquiriu recentemente vários robôs para serem utilizados na vigilância do teatro de operações. Esta dissertação tem como objectivo dimensionar e construir um protótipo de uma antena que visa fazer a comunicação ,sem fios (wireless) entre o operador e o robô usado na vigilância. Este protótipo tem de permitir ao operador alternar entre várias larguras do lobo principal (-3 dB) e ao mesmo tempo vários ganhos. Nesta dissertação foi projetctada, simulada, construída e testada uma antena usando a técnica dos algoritmos genéticos, que permite alterar a largura do lobo principal (-3 dB) e ao mesmo tempo operar com um determinado ganho para essa largura de feixe, sendo assim possível passar de um lobo “estreito” para um mais “largo”. Inicialmente a antena foi dimensionada e simulada no programa de simulação CST MWS, para operar na banda dos 2,4 GHz. Após ter sido construída, a antena foi testada na câmara anecóica e foi verificado se os diagramas de radiação e o coeficiente de onda estacionária correspondiam aos que tinham sido simulados no CST MWS. Estes dados permitem concluir que os diagramas de radiação e o coeficiente de onda estacionária simulados e medidos são muito próximos, sendo que os valores medidos são sempre melhores que os simulados.
Technological progress leads to the appearance of new means and new realities, changing the existing paradigm. . The Portuguese Army also accompanies this development and has recently acquired several robots to be used for surveillance in warfare operations.. This master's thesis aims at designing, build and test a prototype antenna for wireless communication between the operator and the robot used for surveillance. This prototype has to allow the operator to deal with different Half Power Beamwidths and various gains.n The antenna designed and built allows to change the width of the radiation beam, and power gain, thus allowing the operator to use a narrower or wider beam.. Initially the antenna was designed using Genetic Algorithms and simulated using the simulation program CST MWS, to operate in the 2.4 GHz band. The prototype constructed, was tested in an anechoic chamber. A comparison between simulated and experimental results show that the radiation diagrams and the standing wave ratio (SWR) show a good agreement with the results of simulation using the CST MWS software. These data allow us to conclude that the objectives of this thesis were fulfilled and a prototype antenna has a better performance than the simulated one.

A necessidade de antenas para comunicação com sistemas não tripulados, utilizados pelas Forças Armadas, para realizar tarefas de vigilância e reconhecimento levou ao desenvolvimento deste trabalho. A presente dissertação tem como objetivo dimensionar e construir um protótipo de uma antena, que possibilita realizar a comunicação, sem fios entre o operador e os sistemas não tripulados. Este trabalho teve como foco a otimização e realização prática de uma antena ESPAR (Eletronically Steerable Passive Arrays Radiators), utilizando a técnica dos algoritmos genéticos. Esta antena permite um diagrama de radiação direcional e a sua comutação em azimute. Numa fase inicial a antena foi dimensionada e simulada no programa de simulação 4NEC2X, para operar na banda dos 2,4 GHz. A realização do protótipo envolveu uma fase de construção da estrutura básica e outra de inclusão dos componentes eletrónicos. Após construção, a antena foi testada na câmara anecóica e efetuaram-se as medições dos diagramas de radiação e do módulo do parâmetro de dispersão 𝑆11. Os resultados das medições permitem verificar as características diretivas do diagrama de radiação e a comutação do mesmo em azimute, de acordo com as simulações efetuadas e com os objetivos propostos para esta dissertação. No final realiza-se a comparação da antena ESPAR construída no âmbito deste projeto, com uma Yagi-Uda impressa, cujo protótipo foi realizado numa dissertação de mestrado antecedente.
The need for antennas for communication with unmanned systems used by the military to perform surveillance tasks and recognition tasks led to the development of this work. This dissertation has the objective to design and build a prototype of an antenna, which is able to perform wireless communication between the operator and unmanned systems. The work was focused on the optimization and practical use of an ESPAR (Eletronically Steerable Passive Arrays Radiators) antenna, using the technique of genetic algorithms. This antenna allows a directional radiation pattern which can be switched in azimuth. Initially the antenna has been designed and simulated in 4NEC2X simulation program, to operate in the band of 2,4 GHz. The construction of a prototype involved also the construction of a basic structure and the inclusion of electronic components. After construction, the antenna was tested in an anechoic chamber and performed measurements of radiation patterns and the 𝑆11 parameter were performed. The measurement results confirmed the characteristics of directive radiation and the switch of the radiation pattern in azimuth, which is in accordance with the performed simulations. At the end realizes the comparison of ESPAR antenna built as part of this work, with a printed Yagi-Uda, whose prototype was carried out in a previous master's thesis.