PERFORMANCE OF WEARABLE CIRCULARLY POLARIZED ANTENNA ON DIFFERENT HIGH FREQUENCY SUBSTRATES FOR DUAL-BAND WIRELESS APPLICATIONS

This paper proposes the effect of different dielectric constants to construct a microstrip patch antenna deployed on Jean's textile covering military wireless applications. Initially, the structure is designed with double L-shaped slits inserted on both sides of the patch with an FR4 dielectric constant of 4.4. Antenna dimensions are 40 × 25 mm2, which is miniature compared to the wave's length (λ) at the desired operating frequency. The proposed antenna performance in terms of simulated parameters such as gain in dBi, reflection loss (S11), directivity, and patch antenna radiation efficiency are executed by the CST MW EM simulator. However, the conventional way of this design with FR4 may not be so reliable when it is designed on Jean's substrate. Besides all the above parameters extracted from the simulator should hold a low value to implement a high-performance deployed wearable antenna. The paper's outcome shows the importance of simulations and measurements undertaken for the proposed antenna assuming both the dielectric constants of FR4 and Jeans cloth material (with ℇr of 1.7). The main contribution of the antenna is to resonate at the frequencies of 3.17 GHz with circular polarization and 5.04 GHz with linear polarization. The antenna prototype is described, and its performance is validated using measurements. The proposed structure also provides a better enhancement in terms of 10-dB impedance bandwidth, with an average gain of 5 dBi

Antenas setoriais para sistemas de localização em redes de sensores sem fios

Doutoramento em Engenharia EletrotécnicaThis work investigates low cost localization systems (LS) based on received signal strength (RSS) and integrated with different types of antennas with main emphasis on sectorial antennas. The last few years have witnessed an outstanding growth in wireless sensor networks (WSN). Among its various possible applications, the localization field became a major area of research. The localization techniques based on RSS are characterized by simplicity and low cost of integration. The integration of LS based on RSS and sectorial antennas (SA) was proven to provide an effective solution for reducing the number of required nodes of the networks and allows the combination of several techniques, such as RSS and angle of arrival (AoA). This PhD thesis focuses on studying techniques, antennas and protocols that best meet the needs of each LS with main focus on low cost systems based on RSS and AoA. Firstly there are studied localization techniques and system that best suit the requirements of the user and the antennas that are most appropriate according to the nature of the signal. In this step it is intended to provide a fundamental understanding of the undertaken work. Then the developed antennas are presented according to the following categories: sectorial and microstrip antennas. Two sectorial antennas are presented: a narrowband antenna operating at 2.4 to 2.5 GHz and a broadband antenna operating at 800MHz-2.4GHz. The low cost printed antennas were designed to operate at 5 GHz, which may be used for vehicular communication. After presenting the various antennas, several prototypes of indoor/outdoor LS are implemented and analyzed. Localization protocols are also proposed, one based on simplicity and low power, and the other on interoperability with different types of antennas and system requirements.O presente trabalho investiga sistemas de localização (SL) de baixo custo baseados na intensidade do sinal (RSS) e integrados com diferentes tipos de antenas com principal destaque para antenas sectoriais. Os últimos anos testemunharam um crescimento surpreendente de redes de sensores sem fios (RSSF), onde entre diversas aplicações possíveis, a localização tornou-se uma das principais áreas de pesquisa. Técnicas baseadas na intensidade do sinal caracterizam-se pela simplicidade e baixo custo de integração. A integração de SL baseados na intensidade do sinal recebido e antenas sectoriais (AS) oferecem uma solução eficaz para reduzir o número de nós necessários e para combinar diversas técnicas de localização. Esta tese de doutoramento foca-se no estudado de técnicas, antenas e protocolos de acordo com os requisitos de cada sistema localização com especial atenção para sistemas de baixo custo baseados na intensidade do sinal e no ângulo de chegada. Inicialmente são estudadas técnicas e SL de acordo com as necessidades do utilizador e as antenas que melhor se enquadram de acordo com a natureza do sinal. Esta etapa tem como objectivo proporcionar a compreensão fundamental do trabalho desenvolvido. Em seguida são apresentadas as antenas desenvolvidas divididas em: antenas sectorias e antenas impressas de baixo custo. Duas antenas sectoriais são apresentadas: uma de banda estreita a operar a 2,4-2,5GHz e outro de banda larga 800MHz-2.4GHz. As antenas impressas foram desenvolvidas para operar a 5 GHz, pelo que podem ser utilizadas para comunicação veicular. Após apresentação das diversas antenas vários protótipos de SL interiores/exteriores são implementados e analisados. Protocolos de localização são também propostos, um baseado na simplicidade e baixo consumo, outro na interoperabilidade com diferentes tipos de antenas e requisitos do sistema