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Impedance Matching Network for Ground Eliminated Open-ended Resonant Coil Structure in Distributed Wireless Power Transmission Systems
IET Science, Measurement & Technology
Abstract
This study reports a novel technique utilising a standing-wave node as a virtual ground to implement an impedance matching network and power level tuning in a ground eliminated (GE) open-ended resonant coil structure. This technique with GE open-ended coils can potentially be used in wireless power transmission (WPT) systems, where an unknown metallic, ungrounded, arbitrary environment is used as a signal propagation medium to deliver electric power to several distributed nodes. To satisfy WPT standards the proposed resonant WPT system with the matching network is implemented and tested at 13.56 MHz. A comprehensive study of the GE open-ended resonant coil structure demonstrates ground-plane effects and the necessity of an impedance matching network in no-ground signal situations. The experimental results confirm the theoretical analysis presenting 9% improvements in mismatch efficiency, and 13.1 times in power transmission efficiency at 13.56 MHz when the matching network is deployed.
... From the previously described system, it is reasonable to assume that it is possible to substitute the two resonators Fig. 2. Alternative SCPT systems with helical resonator, with (a) a direct connection from the source to the resonator [4], and (b) with a parasitic capacitive feeding structure [5]. ...
... Additionally, different approaches to launch the standing wave into the single conductor are utilized in this paper for comparison (Fig. 2). In Fig. 2a the metallic structure is fed by a direct connection to the AC source and the resonator is kept as one single structure, as presented in [4]. Since such system was designed for a higher frequency, its resonator is physically compact. ...
... The study of open-ended helical coils in the condition of resonance has shown its important characteristics for SCPT [7][8] [11]- [13]. Since its total length is comparable to the wavelength at the frequency of operation, lumped element circuit analysis is not possible and it is necessary to analyze its distributed circuit parameters [12]. ...
... Due to the resemblance with an open-circuit terminated transmission line, the openended helical resonator supports a standing wave with zero current at its open end. The open-ended helical coil or resonator can be fed directly by using a unipolar power source [13] or can be fed using inductive coupling [7] [8], which provides a more convenient two-port input circuitry due to the presence of a regular feeding coil. ...
... However, in this kind of application, the distance and direction of the receiving device relative to the transmitting device will change with user behavior [1], resulting in the unsatisfactory power transmission efficiency. At present, in order to meet the efficiency and power demands for WPT systems, the work mainly focuses on frequency splitting [1,9], automatic frequency adjusting [10][11][12][13][14], impedance matching [15][16][17][18], coil allocating [19,20], etc., where adjusting the natural resonant frequency or the resonant frequency is the main means to promote system efficiency and power. Ref. [10] presented a way of adjusting the natural resonant frequency to reach high output power of a WPT system at a fixed frequency. ...
This work constructs a circuit model, forms a resonant frequency expression of the WPT system, and investigates a novel single side hybrid frequency adjusting strategy. Firstly, by the tracking strategy of minimizing the reflection coefficient, a novel hybrid frequency adjusting control strategy is exerted in the transmitting side by uniting the Bang-Bang control method and the fuzzy PID control technique. Secondly, the receiver is permitted to move to nearly any location within the system's working scope, and the system still reaches a near constant efficiency and a maximum load power. Finally, the simulation results verify that the proposed hybrid adjusting method can be adopted to track the resonant frequency more rapidly and more accurately.
Multi-transmitter wireless power transfer system gets more and more applications due to it can maintain high efficiency in a large space range. This work focuses on modeling the multi-transmitter system, and proposes an impedance matching method to improve efficiency under lateral-misalignment conditions. The theoretical analysis shows that the maximum transfer efficiency can be achieved as long as the equivalent input impedance of the transmitters is regulated to be the same under misalignment condition. Hence, a double closed-loop control strategy is proposed to realize maximum efficiency point tracking, where the primary control loop adjusts the input impedance of the transmitters through PWM while the second control loop maintains constant output power by a DC-DC converter. A 500W prototype is built to validate the feasibility of the proposed method. The efficiency is always higher than 90% with an improvement of up to 20.3% compared to that without such a method when the lateral misalignment increases from 0 to 10cm (0-41% of maximum coil size).
In recent years, monopole antennas have become one of the vital components of cellular mobile communications and internet networks across the globe. Their relatively easy and low fabrication cost and faster installation makes them an obvious choice for developing countries. The most common form is the quarter-wave monopole, in which the antenna is approximately 1/4 of a wavelength of the radio waves. In this paper, we present the analytical treatment of a quarter-wave monopole antenna above virtual ground. Virtual ground is realized by using bent radials around the vertical monopole element. Radiation resistance and gain of the quarter-wave monopole are mathematically derived and three-dimensional radiation patterns are simulated using sinusoidal current distribution. It is observed that for the case of the quarter-wave monopole, we achieve twice the gain of a dipole antenna of half-wavelength long. As the radiated power is limited to upper hemisphere of the ground plane, the total radiated power of the quarter-wave monopole is half of that of a dipole. Hence, the value of radiation resistance of the monopole is half of that of a dipole.
Inductive coupling is a viable scheme to wirelessly energize devices with a wide range of power requirements from nanowatts in radio frequency identification tags to milliwatts in implantable microelectronic devices, watts in mobile electronics, and kilowatts in electric cars. Several analytical methods for estimating the power transfer efficiency (PTE) across inductive power transmission links have been devised based on circuit and electromagnetic theories by electrical engineers and physicists, respectively. However, a direct side-by-side comparison between these two approaches is lacking. Here, we have analyzed the PTE of a pair of capacitively loaded inductors via reflected load theory (RLT) and compared it with a method known as coupled-mode theory (CMT). We have also derived PTE equations for multiple capacitively loaded inductors based on both RLT and CMT. We have proven that both methods basically result in the same set of equations in steady state and either method can be applied for short- or midrange coupling conditions. We have verified the accuracy of both methods through measurements, and also analyzed the transient response of a pair of capacitively loaded inductors. Our analysis shows that the CMT is only applicable to coils with high quality factor (Q) and large coupling distance. It simplifies the analysis by reducing the order of the differential equations by half compared to the circuit theory.
The design and development of a smart monitoring and controlling system for household electrical appliances in real time has been reported in this paper. The system principally monitors electrical parameters of household appliances such as voltage and current and subsequently calculates the power consumed.The novelty of this system is the implementation of the controlling mechanism of appliances in different ways. The developed system is a low-cost and flexible in operation and thus can save electricity expense of the consumers. The prototype has been extensively tested in real-life situations and Experimental results are very encouraging.
Through harvesting energy by wireless charging and delivering data by wireless communication, this study proposes the concept of a wireless sensor enabled by wireless power (WPWS) and reports the fabrication of a prototype for functional tests. One WPWS node consists of wireless power module and sensor module with different chip-type sensors. Its main feature is the dual antenna structure. Following RFID system architecture, a power harvesting antenna was designed to gather power from a standard reader working in the 915 MHz band. Referring to the Modbus protocol, the other wireless communication antenna was integrated on a node to send sensor data in parallel. The dual antenna structure integrates both the advantages of an RFID system and a wireless sensor. Using a standard UHF RFID reader, WPWS can be enabled in a distributed area with a diameter up to 4 m. Working status is similar to that of a passive tag, except that a tag can only be queried statically, while the WPWS can send dynamic data from the sensors. The function is the same as a wireless sensor node. Different WPWSs equipped with temperature and humidity, optical and airflow velocity sensors are tested in this study. All sensors can send back detection data within 8 s. The accuracy is within 8% deviation compared with laboratory equipment. A wireless sensor network enabled by wireless power should be a totally wireless sensor network using WPWS. However, distributed WPWSs only can form a star topology, the simplest topology for constructing a sensor network. Because of shielding effects, it is difficult to apply other complex topologies. Despite this limitation, WPWS still can be used to extend sensor network applications in hazardous environments. Further research is needed to improve WPWS to realize a totally wireless sensor network.
The advances in wireless communication, microelectronics, digital electronics, and highly integrated electronics and the increasing need for more efficient controlled electric systems make the development of monitoring and supervisory control tools the object of study of many researchers. This paper proposes a digital system for energy usage evaluation, condition monitoring, diagnosis, and supervisory control for electric systems applying wireless sensor networks (WSNs) with dynamic power management (DPM). The system is based on two hardware topologies responsible for signal acquisition, processing, and transmission: intelligent sensor modules (ISMs) and remote data acquisition units (RDAUs). The gateway function of the wired network is carried out by remote servers (RSs) based on the Soekris architecture, which is responsible for receiving the data collected and transmitting it to the supervisory controller (SC). To extend the WSN lifetime, sensor nodes implement a DPM protocol. The basic characteristics of the presented system are the following: 1) easy implementation; 2) low-cost implementation; 3) easy implementation of redundant routines (security); 4) portability/versatility; and 5) extended network lifetime.
Wireless power technology offers the promise of cutting the last cord, allowing users to seamlessly recharge mobile devices as easily as data are transmitted through the air. Initial work on the use of magnetically coupled resonators for this purpose has shown promising results. We present new analysis that yields critical insight into the design of practical systems, including the introduction of key figures of merit that can be used to compare systems with vastly different geometries and operating conditions. A circuit model is presented along with a derivation of key system concepts, such as frequency splitting, the maximum operating distance (critical coupling), and the behavior of the system as it becomes undercoupled. This theoretical model is validated against measured data and shows an excellent average coefficient of determination of 0.9875. An adaptive frequency tuning technique is demonstrated, which compensates for efficiency variations encountered when the transmitter-to-receiver distance and/or orientation are varied. The method demonstrated in this paper allows a fixed-load receiver to be moved to nearly any position and/or orientation within the range of the transmitter and still achieve a near-constant efficiency of over 70% for a range of 0-70 cm.
Wireless power transfer via magnetic resonant coupling is experimentally demonstrated in a system with a large source coil and either one or two small receivers. Resonance between source and load coils is achieved with lumped capacitors terminating the coils. A circuit model is developed to describe the system with a single receiver, and extended to describe the system with two receivers. With parameter values chosen to obtain good fits, the circuit models yield transfer frequency responses that are in good agreement with experimental measurements over a range of frequencies that span the resonance. Resonant frequency splitting is observed experimentally and described theoretically for the multiple receiver system. In the single receiver system at resonance, more than 50% of the power that is supplied by the actual source is delivered to the load. In a multiple receiver system, a means for tracking frequency shifts and continuously retuning the lumped capacitances that terminate each receiver coil so as to maximize efficiency is a key issue for future work.
A wireless power transmission system with a dynamic, real-time feedback for impedance matching is presented. The AC signal at the receiver node is rectified, the resulting DC signal is passed to a voltage controlled oscillator which drives a high-frequency analog switch. When in the ON state, the switch shorts the terminals of the receiver coil, dramatically changing the impedance seen by the transmitter coil. This change is detected on the transmitter side as the backscattered signal. Variation on the frequency of the backscattered signal can then be used to affect changes in the power source amplitude or the transmission side matching network to optimize the transmission power efficiency. The proposed feedback system is implemented with planar spiral coils on PCBs, and the effect of distance variation between the coils and as a consequence, DC voltage variation on the rectifier output is measured using voltage signal spectrum in the transmitter node at 1 MHz. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2980–2983, 2016.
The performance of remote estimation over wireless channels is strongly affected by sensor data losses due to interference. Although the impact of interference can be alleviated by applying cognitive radio technique which features in spectrum sensing and transmitting data only on clear channels, the introduction of spectrum sensing incurs extra energy expenditure. In this paper, we investigate the problem of energy-efficient spectrum sensing for remotely estimating the state of a general linear dynamic system, and formulate an optimization problem which minimizes the total sensor energy consumption while guaranteeing a desired level of estimation performance. We model the problem as a mixed integer nonlinear program and propose a simulated annealing based optimization algorithm which jointly addresses when to perform sensing, which channels to sense, in what order and how long to scan each channel. Simulation results demonstrate that the proposed algorithm well balances the sensing energy and transmission energy expenditure and can achieve the desired estimation performance.
Pulmonary vein isolation an effective treatment for atrial fibrillation. Current endocardial ablation techniques require catheter contact for lesion formation. Inadequate or inconsistent catheter contact results in difficulty achieving acute and long-term isolation and consequent atrial arrhythmia recurrence. Microwave energy produces radiant heating and, therefore, can be used for noncontact catheter ablation. We hypothesized that it is possible to design a microwave catheter to produce a circumferential transmural thermal lesion in an in vitro model of a pulmonary vein antrum.
A monopole microwave catheter with a sideways firing axially symmetrical heating pattern was designed. Noncontact ablations were performed in a perfused pulmonary vein model constructed from microwave myocardial phantom embedded with a sheet of thermochromic liquid crystal to permit visualisation and measurement of thermal lesions from colour changes. 1200J ablations were performed at 150W for 80sec and 120W for 100sec at high (0.8L/min) and low (0.06L/min) flow through the modelled pulmonary vein. Myocardial tissue was substituted for the phantom material and ablations repeated at 150W for 180sec and stained with nitro-blue tetrazolium. The catheter was able to induce deep circumferential antral lesions in myocardial phantom and myocardial tissue. More rapid delivery of microwave energy led to a reduced effect of cooling from surface flow as manifested by larger lesions with less surface sparing.
A microwave catheter can be designed to produce a circumferential thermal lesion on noncontact ablation and may have possible applications for pulmonary vein isolation. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
An experimental work aimed at assessing the outdoor-to-indoor propagation losses at 169 MHz is described in this paper. The building penetration loss, often considered as an additional constant value to be added to propagation losses in previous studies, is here on the contrary regarded as a random variable; its cumulative distribution is extracted from the measured data and is found to be approximately Gaussian. Moreover, in order to account for the critical installation conditions which may be experienced by indoor wireless devices in particular applications (e.g., wireless smart metering), an additional loss term, here indicated as installation loss, is introduced and its value is investigated in some reference cases. The achieved results are also embedded into a statistical procedure similar to those commonly adopted for wireless cellular networks planning.
This paper proposes a wireless sensor network system in a rocket and describes the architecture of sensor tags. The proposed health monitoring system based on the wireless sensor network employs MIMO communication systems, dual-band; 5GHz for downlink and 24GHz for uplink, and dual power sources; vibration and electromagnetic. The paper also demonstrates a GaAs pHEMT 20-30 GHz band low-power consumption amplifier MMIC for the sensor system. At 1V supply voltage, the amplifier achieves a gain of 11.4dB at 24.5GHz. The power consumption and the output 1-dB compression point are 6.16mW and -0.8dBm, respectively. The MMIC achieves the highest performances of reported 24-GHz amplifier ICs.
The importance of the experiments realized by Guglielmo Marconi on the premises of Villa Griffone were probably already universally considered a fundamental step for understanding propagation in real environment, a key point in successful operation of a radio system. Thousands of visitors at the Villa and at the Marconi Museum are evidence of that. However, this official recognition by the IEEE that these experiments marked the beginning of the new era of wireless communication is the proper seal for the adventure of the Marconi genius, started in Italy and continued all over the world for more than forty years.
Using self-resonant coils in a strongly coupled regime, we experimentally demonstrated efficient nonradiative power transfer
over distances up to 8 times the radius of the coils. We were able to transfer 60 watts with ∼40% efficiency over distances
in excess of 2 meters. We present a quantitative model describing the power transfer, which matches the experimental results
to within 5%. We discuss the practical applicability of this system and suggest directions for further study.
Method and system for wireless and single conductor power transmission
- A Maunder
- T Zarifi
- P Mousavi
Wireless power transmission: an innovative idea
- Choudhary V.