Compact near field wireless energy transfer systems using defected ground structures

Near-Field Wireless Power Transfer systems have attracted attention for their potential applications, such as implanted medical devices, radio frequency identification, and portable electronic devices in general. In this context, a compact model for short-range NF-WPT systems operating in ISM frequency bands is proposed, employing the concept of ground plane aperture resonators or Defected Ground Structures (DGS). This technique allows the miniaturization of the resonator, which leads to the development of compact NF-WPT systems. The model proposed in this work aims at possible applications that require simultaneous energy and data transfer. This model operates in dual band in 433 MHz and 900 MHz frequency bands and makes use of overlapping circular DGS in order to shrink the resonator device and obtain high values of Figure of Merit (FoM) commonly used in this research area. The proposed model was designed using the electromagnetic analysis and built using Rogers RO4003 dielectric material. The designed dual-band DGS resonators have a total area of 11.7 × 10.2 mm 2 and when placed at a distance of 15 mm between transmitter and receiver, they have measured FoM values of 0.71 and 1.07 at 440 MHz and 918 MHz, respectively. The results were compared with related works found in the literature, and indicate a ηWPT of 40.9% and 49.2 %

Design and Modelling of Wireless Power Transfer and Energy Harvesting Systems

The escalation of the Internet-of-Everything topicality has motivated an increased interest in both academia and industry research for efficient solutions enabling self-sustained smart operations. From the maintenance point of view, indeed, battery-less strategies represent the most valuable way for distributed zero-power standalone electronics. With this purpose, different scavenging techniques are being adopted, gathering energy from different sources such as mechanical, solar, thermal and electromagnetic waves. Due to the wide spread of wireless communication systems, the latter technology has recently benefited a renewed interest. This Ph.D. research activity has been focused on the investigation of new efficient solutions for radiofrequency energy harvesting and wireless power transmission techniques, aiming at improving the state of the art, by also taking into account the imperative necessity of eco-friendly materials for the development of green electronics. The combination of radiofrequency energy harvesting and ultra-wideband techniques is also proposed as possible candidate for future RFID systems. These functionalities are integrated in a novel, compact and low-profile tag, whose details are provided thoroughly from both electromagnetic and nonlinear circuit viewpoints. Results validation is provided through experimental characterization. Compatibility with the environment is assured by implementation with recyclable material. This concept is then extended with the investigation of more elaborated energy scavenging architectures, including rectenna arrays. Finally, a near-field wireless power transmission system is presented on low-cost materials, therefore suitable for possible mass-market deployment

Compact circular polarization filtenna for wireless power transfer applications

Nowadays, Internet of Things (IoT) electronic devices are needed to realize the fifth generation (5G) device-to-device communication. Obviously, current developments tend to focus more towards structure compactness for mobility purposes. However, the main weakness for mobile devices is its power supply. This can be improved by increasing the individual battery capacity or having external batteries. These proposed solutions will increase the weight of the devices, hence making them heavier to carry around. Most total IoT devices are also required to be multi-functional depending on different radio frequencies (RF). Commonly, the RF signal radiated is solely used for data communication. This useful RF signal can also be converted into small energy, instead of being left to disperse into the environment. This relates to wireless energy harvesting called as rectifying antenna (rectenna) which converts RF signal to direct current (DC). A generic rectenna consists of the combination of several components such as antenna, filter, diode and resistive load. The aim of this research is to develop a compact or miniaturized RF front-end component for the rectenna. Compactness can be achieved by embedding the filter into the antenna to form a filtenna. Non-contacted electromagnetic coupling technique with the circular patch antenna operated at 2.45 GHz is selected as the basic design and the simulation work was done using the Computer Simulation Technology (CST) software. To enhance the quality of propagation and the multi-functional properties, the proposed design optimized for circular polarization (CP) and wider bandwidth. Therefore, the modification of the basic design change to proximity coupled feeding technique with double layered configuration is presented. Analysis of the slot line resonator near to the transmission line on several locations is discussed to realize a filtenna. In this research, several different designs of antennas and filters are presented with different compactness, CP, and higher resonant rejection properties. All proposed designs are fabricated and validated through measurement studies. Good agreement is shown between simulation and measurement results. By having approximately 45-50 % of size reduction as compared to the conventional 2.45 GHz microstrip patch antenna, the developed antennas are compact in size with higher resonant rejection up to third harmonic and exhibit 5.2 dB gain

A Review on Antenna Technologies for Ambient RF Energy Harvesting and Wireless Power Transfer: Designs, Challenges and Applications

Radio frequency energy harvesting (RFEH) and wireless power transmission (WPT) are two emerging alternative energy technologies that have the potential to offer wireless energy delivery in the future. One of the key components of RFEH or WPT system is the receiving antenna. The receiving antenna's performance has a considerable impact on the power delivery capability of an RFEH or WPT system. This paper provides a well-rounded review of recent advancements of receiving antennas for RFEH and WPT. Antennas discussed in this paper are categorized as low-profile antennas, multi-band antennas, circularly polarized antennas, and array antennas. A number of contemporary antennas from each category are presented, compared, and discussed with particular emphasis on design approach and performance. Current design and fabrication challenges, future development, open research issues of the antennas and visions for RFEH and WPT are also discussed in this review

WPT, Recent Techniques for Improving System Efficiency

Wireless power transfer (WPT) technologies have received much more attention during the last decade due to their effectiveness in wireless charging for a wide range of electronic devices. To transmit power between two points without a physical link, conventional WPT systems use two coils, one coil is a transmitter (Tx) and the other is a receiver (Rx) which generates an induced current from the received power. Two main factors control the performance of the WPT schemes, power transfer efficiency (PTE) and transmission range. Power transfer efficiency refers to how much power received by the rechargeable device compared to the power transmitted from the transmitter; while transmission range indicates the longest distance between transmitter and receiver at which the receiver can receive power within the acceptable range of power transfer efficiency. Several studies were carried out to improve these two parameters. Many techniques are used for WPT such as inductive coupling, magnetic resonance coupling, and strongly coupled systems. Recently, metamaterial structures are also proposed for further transfer efficiency enhancement. Metamaterials work as an electromagnetic lensing structure that focuses the evanescent transmitted power into receiver direction. Transmitting & Receiving antenna systems may be used for sending power in certain radiation direction. Optimizing the transmitter antenna and receiver antenna characteristics increase the efficiency for WPT systems. This chapter will present a survey on different wireless power transmission schemes

Sistemas compactos de transferência de energia sem fio em campo próximo usando estruturas com abertura no plano de terra

Sistemas de transferência de energia sem fio em campo próximo (NF-WPT, NearField Wireless Power Transfer) tem atraído atenção por suas potenciais aplicações, tais como, dispositivos médicos implantados (IMDs), identificação por rádio frequência (RFID, Radio Frequency Identification) e dispositivos eletrônicos portáteis em geral. Nesse contexto, são propostos modelos compactos para sistemas NF-WPT de curto alcance operando em faixas de frequências ISM empregando o conceito de ressonadores de abertura no plano de terra (DGS, Defected Ground Structure). Essa técnica permite a miniaturiza- ção do ressonador, o que leva ao desenvolvimento de sistemas compactos de NF-WPT. O primeiro modelo proposto neste trabalho, visa possíveis aplicações que requerem transferência de energia e dados simultaneamente. Esse modelo opera em banda dupla nas faixas de frequências de 433 MHz e 900 MHz e faz o uso de DGS circulares sobrepostas a fim de compactar o dispositivo ressonador e obter altos valores de figura de mérito (FoM) comumente empregadas na área de pesquisa. Dessa forma, busca-se contribuir para o avanço do estado da arte dos sistemas WPT baseados em DGS de banda dupla. O segundo modelo proposto visa manter o conceito de compactação dos ressonadores mesmo em faixas de frequências mais baixas. São apresentados o desenvolvimento, construção e medição dos sistemas de WPT usando dispositivos ressonantes baseados em DGS projetados para as faixas de frequências ISM de 6,78 MHz, 27,12 MHz e 40,68 MHz. Ambos os modelos propostos são projetados utilizando o software de análise eletromagnética (EM) Ansys Electronics e são construídos utilizando o material dielétrico Rogers RO4003. Os ressonadores DGS de banda dupla projetados possuem uma área total de 11,7 x 10,2 mm2 e ao serem posicionados a uma distância de 15 mm entre transmissor e receptor apresentam valores de FoM medidas de 0,71 e 1,07 em 440 MHz e 918 MHz, respectivamente. Dois sistemas de banda única foram projetados usando o mesmo dispositivo DGS com dimensões de 13 x 14 mm2 e apresentaram FoM medidas de 0,65 e 0,75, a uma distância de 20 mm, respectivamente, para as frequências de 27,25 MHz e 40,25 MHz. Já o sistema projetado na faixa de frequência de 6,78 MHz, apresentou uma FoM de 0,48 a uma distância de 35 mm usando dispositivos com dimensões de 32 x 35,5 mm2. Os resultados são comparados com trabalhos relacionados encontrados na literatura.Near-field wireless power transfer systems (NF-WPT) have been attracting attention for their potential applications such as implantable medical devices (IMDs), radio frequency identification (RFID) and portable electronic devices. In this context, compact models are proposed for NF-WPT systems in industrial, scientific and medical (ISM) bands employing the concept of defected ground structure (DGS) resonators. This technique allows the miniaturization of the resonator, which leads to the development of compact NF-WPT systems. The first model that is proposed in this work aims at possible applications that require energy and data transfer simultaneously. It operates in dual band in the frequency bands of 433 MHz and 900 MHz and uses circulars superimposed DGS in order to compact the resonator device and obtain high values of figure of merit (FoM), commonly employed in the search area. In this way, the aim is to contribute to the advancement of the state of the art of WPT systems based on dual-band DGS. The second model proposed aims to maintain the concept of resonator compaction even in lower frequency bands. Three projects are presented in detail from the design to the construction and measurement of WPT systems using resonant devices based on DGS designed in the frequency bands of 6.78 MHz, 27.12 MHz and 40.68 MHz. Both models for proposed NF-WPT systems are designed using the Ansys Electronics electromagnetic analysis software and are built using Rogers RO4003 dielectric material. Dual-band DGS resonators have a total area of 11.7 x 10.2 mm2 and an optimal WPT distance of 15 mm between transmitter and receiver. At this distance, the FoMs are measured and presented 0.71 and 1.07 at 440 MHz and 918 MHz, respectively. Two single-band systems are designed using the same DGS device with dimensions of 13 x 14 mm2 and presented FoM measures of 0.65 and 0.75, at a distance of 20 mm, respectively, for the frequencies of 27.25 MHz and 40.25 MHz. The system, designed in the frequency range of 6.78 MHz, presented a FoM of 0.48 at an optimized 35 mm WPT distance using devices with dimensions of 32 x 35.5 mm2. The results are discussed and compared with related works found in the literature

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Applications of Antenna Technology in Sensors

During the past few decades, information technologies have been evolving at a tremendous rate, causing profound changes to our world and to our ways of living. Emerging applications have opened u[ new routes and set new trends for antenna sensors. With the advent of the Internet of Things (IoT), the adaptation of antenna technologies for sensor and sensing applications has become more important. Now, the antennas must be reconfigurable, flexible, low profile, and low-cost, for applications from airborne and vehicles, to machine-to-machine, IoT, 5G, etc. This reprint aims to introduce and treat a series of advanced and emerging topics in the field of antenna sensors