Microwave Antennas for Energy Harvesting Applications

In the last few years, the demand for power has increased; therefore, the need for alternate energy sources has become essential. Sources of fossil fuels are finite, are costly, and causes environmental hazard. Sustainable, environmentally benign energy can be derived from nuclear fission or captured from ambient sources. Large-scale ambient energy is widely available and large-scale technologies are being developed to efficiently capture it. At the other end of the scale, there are small amounts of wasted energy that could be useful if captured. There are various types of external energy sources such as solar, thermal, wind, and RF energy. Energy has been harvested for different purposes in the last few recent years. Energy harvesting from inexhaustible sources with no adverse environmental effect can provide unlimited energy for harvesting in a way of powering an embedded system from the environment. It could be RF energy harvesting by using antennas that can be held on the car glass or building, or in any places. The abundant RF energy is harvested from surrounding sources. This chapter focuses on RF energy harvesting in which the abundant RF energy from surrounding sources, such as nearby mobile phones, wireless LANs (WLANs), Wi-Fi, FM/AM radio signals, and broadcast television signals or DTV, is captured by a receiving antenna and rectified into a usable DC voltage. A practical approach for RF energy harvesting design and management of the harvested and available energy for wireless sensor networks is to improve the energy efficiency and large accepted antenna gain. The emerging self-powered systems challenge and dictate the direction of research in energy harvesting (EH). There are a lot of applications of energy harvesting such as wireless weather stations, car tire pressure monitors, implantable medical devices, traffic alert signs, and mars rover. A lot of researches are done to create several designs of rectenna (antenna and rectifier) that meet various objectives for use in RF energy harvesting, whatever opaque or transparent. However, most of the designed antennas are opaque and prevent the sunlight to pass through, so it is hard to put it on the car glass or window. Thus, there should be a design for transparent antenna that allows the sunlight to pass through. Among various antennas, microstrip patch antennas are widely used because they are low profile, are lightweight, and have planar structure. Microstrip patch-structured rectennas are evaluated and compared with an emphasis on the various methods adopted to obtain a rectenna with harmonic rejection functionality, frequency, and polarization selectivity. Multiple frequency bands are tapped for energy harvesting, and this aspect of the implementation is one of the main focus points. The bands targeted for harvesting in this chapter will be those that are the most readily available to the general population. These include Wi-Fi hotspots, as well as cellular (900/850 MHz band), personal communications services (1800/1900 MHz band), and sources of 2.4 GHz and WiMAX (2.3/3.5 GHz) network transmitters. On the other hand, at high frequency, advances in nanotechnology have led to the development of semiconductor-based solar cells, nanoscale antennas for power harvesting applications, and integration of antennas into solar cells to design low-cost light-weight systems. The role of nanoantenna system is transforming thermal energy provided by the sun to electricity. Nanoantennas target the mid-infrared wavelengths where conventional photo voltaic cells are inefficient. However, the concept of using optical rectenna for harvesting solar energy was first introduced four decades ago. Recently, it has invited a surge of interest, with different laboratories around the world working on various aspects of the technology. The result is a technology that can be efficient and inexpensive, requiring only low-cost materials. Unlike conventional solar cells that harvest energy in visible light frequency range. Since the UV frequency range is much greater than visible light, we consider the quantum mechanical behavior of a driven particle in nanoscale antennas for power harvesting applications

A New Fractal-Based Miniaturized Dual Band Patch Antenna for RF Energy Harvesting

The growth of wireless communications in recent years has made it necessary to develop compact, lightweight multiband antennas. Compact antennas can achieve the same performance as large antennas do with low price and with greater system integration. Dual-frequency microstrip antennas for transmission and reception represent promising approach for doubling the system capacity. In this work, a miniaturized dual band antenna operable at 2.45 and 5.8 GHz is constructed by modifying the standard microstrip patch antenna geometry into a fractal structure. In addition to miniaturization and dual band nature, the proposed antenna also removes unwanted harmonics without the use of additional filter component. Using a finite-element-method-based high frequency structure simulator (HFSS), the antenna is designed and its performance in terms of return loss, impedance matching, radiation pattern, and voltage standing wave ratio (VSWR) is demonstrated. Simulation results are shown to be in close agreement with performance measurements from an actual antenna fabricated on an FR4 substrate. The proposed antenna can be integrated with a rectifier circuit to develop a compact rectenna that can harvest RF energy in both of these frequency bands at a reduction in size of 25.98% relative to a conventional rectangular patch antenna

Rectifier Circuit Designs for RF Energy Harvesting applications

International audienceRF energy scavenging, commonly referred to as RF energy harvesting, is the capability of collecting ambient RF energy from antennas to supply power to electronic devices. The rectifier circuit is the key component of wireless energy harvesting system. Therefore, the development of efficient and compact rectifier circuit has become recently a vital research topic. This paper presents a state of the art and review of the recent designs of microstrip recti- fier circuit used for RF energy harvesting applications at 2.45 GHz and 5.8GHz

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

Optically transparent UWB antenna for wireless application & energy harvesting

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Transparent UWB antennas have been the focus of this PhD research. The use of transparent UWB antennas for stealth and energy harvesting has been the underlying applications that have given impetus to this research. Such transparent antennas being built on materials that are discreet, flexible, conformal, conductive and having the ability to provide good antenna performance on glass to serve as the ‘last mile’ link in subsequent generation communications after 4G have been the basis for this contention. UWB in this regard is able to provide the transmission and reception of high data rates and fast video transmission that is an elementary demand of even a 4G wireless communications system. The integration of UWB antennas with photovoltaic to provide integral energy harvesting solutions that will further enhance the value of the UWB system in terms of cost effectiveness and performance are thus the basis of this work. This work hence starts with the study of a transparent conductive oxide polymer, AgHT and its properties, and culminates in the development of a transparent UWB antenna, which can be integrated with photovoltaic for window glass applications on homes and buildings. Other applications such transparent antennas can find use for like on-body wireless communications in healthcare monitoring was also analysed and presented. The radar absorbing material (RAM) property of the AgHT was investigated and highlighted using CST simulation software, as no measurement facilities were available. The transparent UWB antenna in lieu of the inherent absorbent property of the AgHT material is thus able to exhibit stealth characteristics, a feature that would be much desired in military communications. Introduction of a novel method of connecting the co-axial connector to the feed of the antenna to improve gain and efficiency of transparent polymer based antennas and the development of a UWB antenna that maintains its Omni-directional characteristic instead of becoming directional on an amorphous silicon solar cell are presented as some of the contributions for this research work. Some preliminary analysis on the impact of glass on UWB antennas for video transmission and how to improve transmission is presented. The ability of the conductive part of the antenna radiator to be used as a RF and microwave harvester and how it can further add value to a transparent UWB antenna is presented by way of experimental data. Finally yet importantly, this thesis presents some insight into how transparent antennas may be used in Green Technology Buildings to provide an integrated solution for both wireless communications and energy harvesting as part of the future work. Improvement to the aesthetics of the external appearance of residential buildings through the integration of transparent satellite dish onto solar panels on rooftops is also discussed and illustrated as part of this future work

A Triple Band Bow Tie Array Antenna Using Both-sided MIC Technology

A single-fed linearly polarized 2x2 microstrip bow tie array antenna is proposed. The feed network has microstrip line and slot line where microstrip-slot branch circuit is connected in parallel. The feed network of the array is designed using both-sided MIC Technology to overcome the impedance matching problem of conventional feed networks. The 2x2 half bow tie array antenna is also truncated with spur lines for optimization of antenna performance. The array antenna unit can be realized in very simple and compact structure, as all the antenna elements and the feeding circuit is arranged on a Teflon glass fiber substrate without requiring any external network. The design frequency of the proposed antenna is 5 to 8 GHz (CBand) and the obtained peak gain is 12.41 dBi. The resultant axial ratio indicates that linear polarization is achieved.

2.45 GHz Rectenna With High Gain For RF Energy Harvesting

This paper presents a high gain rectenna at 2.45 GHz. Two layers low cost FR4 substrate has been used with air-gap technology for this fabricated rectenna. The proposed designs contain antenna and open stub rectifying circuits with feedline. With the dimension of 100x100x5 mm3, this rectenna can perform high gain. The technique of air gap approach has been used for this proposed rectenna design so as to increase the antenna gain. Second and third harmonics has been eliminated by the introducing of triangular slot and ground plane to the developed design. The proposed rectenna successfully achievedthe output voltages reaches 0.46 V when the input power is 0 dBm respectively when the input power range is between -25 to 30 dBm. It is also can reach up to 6V when the maximum input power is applied. High gain, simple design, low profile and easy integration are the main advantages of this design of the rectenna when compared to past researchers

Design and implementation of band rejected antennas using adaptive surface meshing and genetic algorithms methods. Simulation and measurement of microstrip antennas with the ability of harmonic rejection for wireless and mobile applications including the antenna design optimisation using genetic algorithms.

With the advances in wireless communication systems, antennas with different shapes and design have achieved great demand and are desirable for many uses such as personal communication systems, and other applications involving wireless communication. This has resulted in different shapes and types of antenna design in order to achieve different antenna characteristic. One attractive approach to the design of antennas is to suppress or attenuate harmonic contents due to the non-linear operation of the Radio Frequency (RF) front end. The objectives of this work were to investigate, design and implement antennas for harmonic suppression with the aid of a genetic algorithm (GA). Several microstrip patch antennas were designed to operate at frequencies 1.0, 1.8 and 2.4 GHz respectively. The microstrip patch antenna with stub tuned microstrip lines was also employed at 1.0 and 1.8 GHz to meet the design objectives. A new sensing patch technique is introduced and applied in order to find the accepted power at harmonic frequencies. The evaluation of the measured power accepted at the antenna feed port was done using an electromagnetic (EM) simulator, Ansoft Designer, in terms of current distribution. A two sensors method is presented on one antenna prototype to estimate the accepted power at three frequencies. The computational method is based on an integral equation solver using adaptive surface meshing driven by a genetic algorithm. Several examples are demonstrated, including design of coaxially-fed, air-dielectric patch antennas implanted with shorting and folded walls. The characteristics of the antennas in terms of the impedance responses and far field radiation patterns are discussed. The results in terms of the radiation performance are addressed, and compared to measurements. The presented results of these antennas show a good impedance matching at the fundamental frequency with good suppression achieved at the second and third harmonic frequencies.Home governmen