Multitone excitation analysis in RF energy harvesters—Considerations and limitations

© 2018 IEEE. The effect of multitone excitation on the dc response of a voltage-doubler radio frequency energy harvester is analyzed. Theoretical analysis as well as frequency and time domain (TD) simulations were conducted to clarify the findings. Measurements were also carried out to validate the results. The measured, simulations and theoretical results are in good agreement. This paper focuses on evaluating the performance of a voltage doubler rectifier under multitone excitation (input power is the same in the single-tone and multitone case). Based on TD and harmonic balance simulations, theoretical and measurement analyses, it is evident that the application of multiple tones simultaneously within the matched frequency band and with the same average available power results in a lower average output dc power when compared with the single-tone case with the same input power. This trend is evident over a broad low input power range of −50 to −10 dBm (0.01–100 µW)

Power Flow Control in Multi-Terminal HVDC Grids Using a Serial-Parallel DC Power Flow Controller

© 2013 IEEE. Multi-terminal HVDC (MT-HVDC) grids have no capability of power flow control in a self-sufficient manner. To address this important issue, utilization of dc-dc high power and high-voltage converters is motivated. However, proposing suitable partial-rated dc-dc converters as well as their suitable modeling and control in both primary and secondary control layers as well as the stability analysis are the existing challenges that should be alleviated beforehand. This paper addresses the control of power flow problem through the application of a power converter with a different connection configuration, namely, serial parallel dc power flow controller (SPDC-PFC). The SPDC-PFC input is the transmission line voltage, and its output is transmission line current. Therefore, employing a full-power dc-dc converter is avoided as a merit. Additionally, in this paper, the common two-layer MT-HVDC grid control framework comprised of primary and secondary layers is efficiently modified in order to integrate the SPDC-PFC. A differential direct voltage versus active power droop control scheme is applied to the SPDC-PFC at the local control layer, guaranteeing dynamic stability, while an extended dc power-flow routine - integrating the SPDC-PFC - is developed at the secondary control layer to ensure the static stability of the entire MT-HVDC grid. The proposed control framework enables the SPDC-PFC to regulate the flow of current/power in the envisioned HVDC transmission line. From the static and dynamic simulation results conducted on the test CIGRE B4 MT-HVDC grid, successful operation of the proposed SPDC-PFC and control solutions are demonstrated by considering power flow control action. In more detail, the SPDC-PFC successfully regulates the compensated lines' power to the desired reference both in static and dynamic simulations by introducing suitable compensation voltages. In addition, good dynamic performance under both SPDC-PFC power reference and wind power-infeed change is observed

Determination of LC50 of copper in Litopenaeus vannamei

We determined the LC50 of copper (as CUSO_4) and it's Maximum Allowable Concentration (MAC) for Litopenaeus vannamei. The study was performed in 2003 for which bioassays were used for acute toxicity tests in a period of 96 hours during which water parameters such as water temperature, pH, dissolved oxygen, hardness, alkalinity were also measured. Ten treatments and three replicates for each treatment were used. A LC50 of 86.71, 27.28, 7.98 and 3.90mg/1 and also Maximum Allowable Concentration of 8.671, 2.728, 0.798 and 0.390mg/1 were determined at 24, 48, 72 and 96 hours post exposure. Results showed that L. vannamei is relatively resistant to copper. Hence, short period application of copper to white shrimp farms for controlling algal bloom is judged harmless to the fish

Addressing coverage problem in wireless sensor networks based on evolutionary algorithms

© 2017 University of Western Australia. Wireless Sensor Networks (WSNs) are the key part of Internet of Things, as they provide the physical interface between on-field information and backbone analytic engines. An important role of WSNs-when collecting vital information-is to provide a consistent and reliable coverage. To Achieve this, WSNs must implement a highly reliable and efficient coverage recovery algorithm. In this paper, we take a fresh new approach to coverage recovery based on evolutionary algorithms. We propose EMACB-SA, which introduces a new evolutionary algorithm that selects coverage sets using a fitness function that balances energy efficiency and redundancy. The proposed algorithm improves network's coverage and lifetime in areas with heterogeneous event rate in comparison to previous works and hence, it is suitable for using in disaster management

High-Sensitivity and Compact Time Domain Soil Moisture Sensor Using Dispersive Phase Shifter for Complex Permittivity Measurement

This article presents a time domain transmissometry soil moisture sensor (TDT-SMS) using a dispersive phase shifter (DPS), consisting of an interdigital capacitor that is loaded with a stacked four-turn complementary spiral resonator (S4-CSR). Soil moisture measurement technique of the proposed sensor is based on the complex permittivity sensing property of a DPS in time domain. Soil relative permittivity which varies with its moisture content is measured by burying the DPS under a soil mass and changing its phase difference while excited with a 114-MHz sine wave (single tone). DPS output phase and magnitude are compared with the reference signal and measured with a phase/loss detector. The proposed sensor exhibits accuracy better than ±1.2% at the highest volumetric water content (VWC = 30%) for sandy-type soil. Precise design guide is developed and simulations are performed to achieve a highly sensitive sensor. The measurement results validate the accuracy of theoretical analysis and design procedure. Owning the advantages of low profile, low power consumption, and high sensitivity makes the proposed TDT-SMS a good candidate for precision farming and internet of things (IoT) systems

Sensitive ambient RF Energy harvesting

Rectification of microwave signals to generate DC (Direct Current) power has become the subject of research since the 1950’s. Radio Frequency (RF) energy harvesting has experienced a rapid development in recent years due to the increasing number of RF transmitter sources producing an abundant ambient microwave energy waste. Furthermore, the development of wireless power transmission (WPT) technologies has triggered impetus for RF energy harvesting. Hence, RF energy scavenging is a promising solution as it has the potential to provide a viable energy source to meet upcoming demands. Efficient ambient RF energy scavenging is a very challenging issue, as it deals with the low RF power levels available in the environment. The scavengeable power levels are generally unknown and can vary unpredictably; therefore sparking research interest to develop highly sensitive RF energy scavengers to capture ambient RF signals over a range of low input power levels. This research focuses on a real life RF energy scavenging approach to generate electrical power in urban environments. It aims to develop highly sensitive and efficient ambient RF energy scavenging system and method to harvest a broad range of very low level ambient RF power. The feasibility of RF energy harvesting through field measurements and maximum available power analysis in metropolitan areas of Melbourne, Australia is investigated. Scavengeable ambient frequency sources with their associated available RF power levels were identified. RF field investigations and analysis identified the scavengeable levels of ambient RF power are lower than previous published works. Available bands vary considerably from location to location which are highly incoherent and are effected by environmental/free-space conditions. Furthermore, it is demonstrated that commercial frequency bands such as FM (88-108 MHz) and TV (470-890 MHz) provide optimal sources for power scavenging due to their suitable level of the ambient power at a variety of locations. Furthermore, cellular and wireless communication systems (800-1000 MHz) are recommended as alternative power scavenging sources. In order to investigate the feasibility of harvesting ambient EM (electromagnetic) energy from multiple sources (broadcasting and cellular systems) simultaneously, a new highly sensitive multi-resonant rectifier is proposed operating over a broad input power range (−40 to −10 dBm). The measurement results demonstrate that a two tone input to the proposed dual-band RF energy harvesting system can generate 3.14 and 7.24 times more DC power than a single tone at 490 and 860 MHz respectively, resulting in a measured effective efficiency of 54.3% for a dual-tone input power of −10 dBm. Real environmental measurements indicate the rectifier generates 39.38 µW by harvesting RF energy from two bands simultaneously. In order to increase the sensitivity and hence the output DC power, harvesting energy over a wider frequency band is investigated. Therefore, the feasibility of harvesting ambient EM energy from FM broadcasting band is examined. A highly sensitive rectenna is proposed which exhibits favourable impedance matching at 89-11 MHz over a broad range of low input power 50 to 10 dBm (0.01 to 100 µW). The proposed FM rectenna with 22% fractional bandwidth delivers a measured power conversion efficiency of 41% with single tone of −10 dBm. An innovative idea that arose from these investigations was an evaluation of the performance of a rectenna system which was embedded into low profile building materials. This enables to harvest ambient RF energy in urban environments, providing a unique way of delivering power to many low energy home or office devices. Based on the real environmental measurements, the embedded rectenna in plaster generates 175 μW of DC power by harvesting EM energy over the FM frequency band. Finally, the effect of multi-tone excitation (with constant total input power) on output DC power of the rectifier is analysed to facilitate the comparison between single tone and multiple tones. Various factors such as; different frequency spacing, low input power levels and random phase (incoherency) arrangements were considered in frequency and time domain analysis and also in measurements. It is demonstrated that the application of multiple tones simultaneously within the matched frequency band and with constant total input power results in a lower total average output power when compared with single-tone case with the same input power

Wide-angle metamaterial absorber with highly insensitive absorption for TE and TM modes.

Being incident and polarization angle insensitive are crucial characteristics of metamaterial perfect absorbers due to the variety of incident signals. In the case of incident angles insensitivity, facing transverse electric (TE) and transverse magnetic (TM) waves affect the absorption ratio significantly. In this scientific report, a crescent shape resonator has been introduced that provides over 99% absorption ratio for all polarization angles, as well as 70% and 93% efficiencies for different incident angles up to [Formula: see text] for TE and TM polarized waves, respectively. Moreover, the insensitivity for TE and TM modes can be adjusted due to the semi-symmetric structure. By adjusting the structure parameters, the absorption ratio for TE and TM waves at [Formula: see text] has been increased to 83% and 97%, respectively. This structure has been designed to operate at 5 GHz spectrum to absorb undesired signals generated due to the growing adoption of Wi-Fi networks. Finally, the proposed absorber has been fabricated in a [Formula: see text] array structure on FR-4 substrate. Strong correlation between measurement and simulation results validates the design procedure

Low-profile dual-band pixelated defected ground antenna for multistandard IoT devices.

A low-profile dual-band pixelated defected ground antenna has been proposed at 3.5 GHz and 5.8 GHz bands. This work presents a flexible design guide for achieving single-band and dual-band antenna using pixelated defected ground (PDG). The unique pixelated defected ground has been designed using the binary particle swarm optimization (BPSO) algorithm. Computer Simulation Technology Microwave Studio incorporated with Matlab has been utilized in the antenna design process. The PDG configuration provides freedom of exploration to achieve the desired antenna performance. Compact antenna design can be achieved by making the best use of designated design space on the defected ground (DG) plane. Further, a V-shaped transfer function based on BPSO with fast convergence allows us to efficiently implement the PDG technique. In the design procedure, pixelization is applied to a small rectangular region of the ground plane. The square pixels on the designated defected ground area of the antenna have been formed using a binary bit string, consisting of 512 bits taken during each iteration of the algorithm. The PDG method is concerned with the shape of the DG and does not rely on the geometrical dimension analysis used in traditional defected ground antennas. Initially, three single band antennas have been designed at 3.5 GHz, 5.2 GHz and 5.8 GHz using PDG technique. Finally, same PDG area has been used to design a dual-band antenna at 3.5 GHz and 5.8 GHz. The proposed antenna exhibits almost omnidirectional radiation performance with nearly 90% efficiency. It also shows dual radiation pattern property with similar patterns having different polarizations at each operational band. The antenna is fabricated on a ROGERS RO4003 substrate with 1.52 mm thickness. Reflection coefficient and radiation patterns are measured to validate its performance. The simulated and measured results of the antenna are closely correlated. The proposed antenna is suitable for different applications in Internet of Things

Histopathological changes of gill, liver and kidney in Caspian kutum exposed to Linear Alkylbenzene Sulfonate

The histopathological effects of Linear Alkylbenzene Sulfonate on the gill, liver and kidney tissues of the Caspian kutum, Rutilus frisii kutum were studied. The fish were exposed to three sublethal concentrations of anionic detergent, Linear Alkylbenzene Sulfonate (LAS) for short term intervals (192 h). Gill, liver and kidney samples were collected after 192 h of exposure to LAS and lesions were analyzed by light microscopy. The histological changes to gills were edema, fusion of lamellae and lamellar aneurism. Some alterations like reduction of the interstitial haematopoietic tissue, tubular shrinkage, degeneration in the epithelial cells of renal tubule and necrosis were observed in the kidney. In the liver tissue, hepatocyte degeneration, congestion and dilation of sinusoid and vacuolar degeneration were seen. It seems that sublethal concentration of LAS may affect severe changes to gill, kidney and liver of R. frisii kutum specimens that leads to malfunction of these organs which cause damage to health of the fish