Search Results (46)

This work proposes a polarization-insensitive scalable wide-angle metasurface array for highly efficient ambient energy harvesting in the 5.8 GHz Wi-Fi band. Inspired by dipole antenna principles, we design an asymmetric planar orthogonal dipole-based metasurface featuring monolithic integration of Schottky diodes (HSMS-2860) at unit cell feed gaps. This novel direct-impedance-matching strategy eliminates conventional matching networks, reducing energy conversion losses while enabling 99% radiation-to-AC efficiency across all polarization angles at 5.8 GHz. The coplanar architecture interconnects metasurface unit cells via inductors, simultaneously establishing low-loss DC channels and suppressing RF leakage. Fabricated as a 5 × 5 array, the prototype achieves 77.9% peak RF-to-DC efficiency with polarization insensitivity at an incident power of 25 dBm. Furthermore, with incident powers of 15 dBm and 20 dBm, the proposed metasurface array attained RF-to-DC conversion efficiencies exceeding 40% and 60%, respectively. This result indicates that the array is capable of achieving high energy harvesting efficiency across a broad power range. This scalable, drill-free, and polarization-insensitive design demonstrates strong potential for harvesting ambient RF energy in real-world multipath environments. Full article

This study examines the design, manufacturing, and testing of planar PCB inductors (spiral and toroid), including multilayer PCB toroid configurations. These inductors are intended for environments with strong magnetic fields, such as high-energy physics experiments and medical applications, where traditional inductors with ferromagnetic cores are unsuitable. Twelve inductor samples were manufactured and tested. The focus was on maximizing inductance and evaluating performance in a high-frequency DC-DC step-down converter. Key parameters measured included inductance, resistance, thermal performance, electromagnetic interference (EMI), and frequency-dependent behavior in multilayer PCB implementations. The results showed that planar spiral inductors handled higher currents and achieved better efficiency, reaching up to 74.86%. Planar toroid inductors were more tolerant of added shielding, maintaining their inductance, while multilayer toroid designs exhibited reduced DC resistance but increased frequency dependence and sensitivity to parasitic effects. Overall, planar inductors were found to be viable for applications where ferromagnetic cores are unsuitable. Further optimization of geometry, layer configuration, and manufacturing processes could enhance their performance. Full article

This paper proposes a single-stage three-phase AC-DC converter based on an LLC resonant topology utilizing a front-end matrix switch. Unlike traditional two-stage solutions, the proposed topology synthesizes a fluctuating equivalent DC voltage from the three-phase input, achieving direct power conversion with high efficiency. To maintain a stable DC output voltage against the time-varying input, a trajectory-based Pulse Frequency Modulation (PFM) control strategy is developed. By employing State-Plane Analysis (SPA), the operational trajectory is divided into four calculation segments, allowing precise derivation of the switching frequency and duty cycles for both boost and buck modes within a single line cycle. Furthermore, to improve power density and reduce parasitic parameters, a high-frequency planar inductor with interleaved windings and a planar transformer are designed for 500 kHz operation. A pipeline control architecture based on a single DSP is implemented to handle the complex real-time computations. A 500 W prototype is built and tested under 100 V input and 130 V output conditions. Experimental results demonstrate that the converter achieves a peak efficiency of 97%, a power factor of 0.99, and a grid current Total Harmonic Distortion (THD) of 3.95%, validating the effectiveness of the proposed topology and control scheme. Full article

This work presents the design, fabrication, and characterization of a three-dimensional FeCo-based flux-modulator microwinding intended for integration into high-torque axial-flux Vernier micromotors. The proposed micromotor architecture modulates the stator magnetic flux using 12 magnetically isolated FeCo teeth interacting with an 11-pole permanent-magnet rotor. The design requires the manufacturing of complex three-dimensional micrometric parts, including three teeth and a cylindrical core. Such a complex design cannot be manufactured using conventional micromanufacturing lithography or 2D planar methods. The flux-modulator envelope dimensions are 250 μm outer diameter and 355 μm height. It is manufactured using a femtosecond laser-machining process that preserves factory-finished surfaces and minimizes heat-affected zones. In addition, this micrometric part has been wound using 20 μm diameter enamelled copper wire. A dedicated magnetic clamping fixture is developed to enable multilayer microwinding of the integrated core, producing a 17-turn inductor with a 60.6% fill factor—the highest reported for a manually wound ferromagnetic-core microcoil of this scale. Geometric and magnetic characterization validates the simulation model and demonstrates the field distribution inside the isolated core. The results establish a viable micromanufacturing workflow for complex 3D FeCo microwindings, supporting the development of next-generation high-performance MEMS micromotors. Full article

With the development of distributed electric propulsion aircraft, researching airborne high-efficiency, high-power-density, high-gain, high-dynamic and low-ripple, low-stress DC-DC that meets aviation standards is an urgent and profoundly challenging task (Research Background). We propose a new topology to implement related applications. The new topology consists of an interleaved switched-inductor unit for a high-gain, low-ripple, and high-dynamic response, and a switched-capacitor unit for secondary boosting and low voltage stress. This study first analyzes in depth the operating principle and electrical characteristics of the proposed topology in different modes, showing that the proposed topology can achieve an extremely high voltage gain while maintaining low voltage stress. Moreover, the proposed topology employs interleaved inverse coupled inductors to eliminate right-half-plane zero (RHPZ). We establish a universal design guideline for coupled inductors by deriving the equivalent inductance equations, and we implement an ultra-lightweight switched-coupled inductor using planar thin-film integrated magnetic technology. We conduct small-signal modeling to verify the loop characteristics and stability of the proposed converter. Finally, the correctness of the theoretical analysis and the advantages of the proposed converter were verified through a 5000 W experimental prototype and comprehensive comparative experiments. Full article

As integrated electronic microsystems advance, their internal components demonstrate increasing miniaturization, higher-density integration, and, consequently, significantly enhanced performance. This paper presents an on-chip transformer balun. The balun has a combination of planar coupled inductors and filtering capacitors using integrated passive device (IPD) technology, giving it the advantages of a more compact circuit size and lower cost to achieve single-ended to differential function on glass substrates. Moreover, it can be integrated in systems by flip-chip. The die has a size of 1.81 mm × 1.36 mm with a −15 dB single-ended return loss bandwidth of 2.07 GHz to 4.30 GHz. Within this bandwidth, the maximum insertion loss is 2.56 dB, and the amplitude imbalance is less than 2.04 dB. The phase difference between the differential signals is 180 ± 14.02° and the common mode rejection ratio (CMRR) is above 19.08 dB. The balun has the potential of miniaturization for integration on package or through-glass interposers (TGIs). Full article

The most used spiral inductors, in the available scientific literature and in our research activities, so far, have been those with square, hexagonal, octagonal, and circular geometric shapes. Geometry plays an important role in the efficiency of these inductors when used in wireless power transfer. In this article, a new geometric shape is designed by combining the square and the circle to create an oval shape of a planar spiral inductor. Inductors with this new shape are designed, numerically modelled, and practically constructed for experimental testing. The formula for inductance computation for planar spiral inductors is adapted for this new oval shape. New geometric coefficients, required for inductance computation formula, have been determined. The new formula for inductance computation is validated both analytically, by comparing the results with those from numerical modelling, and experimentally, by comparing with measurements, for a wide range of oval spiral inductors. Five sets of different oval spiral inductors are optimally designed, numerically modelled, practically constructed, and experimentally tested. By designing this new shape for planar spiral inductors, the inductance is increased 2.16 times compared to square, 1.84 times compared to hexagonal, 2.12 times compared to octagonal, and 2.52 times compared to circular shapes. The new oval spiral inductor design will be very useful for constructing wireless power transfer systems for pacemakers, smartphones, smartwatches, and/or any other type of smart device. Full article

In traditional inductor design with planar windings, the magnetic field distribution may not be well-organized, leading to significant winding loss, particularly at high switching frequencies. This study explores the relationship between current distribution and magnetic field distribution in the winding region. Unlike conventional magnetic flux distribution, which directs a large portion of the magnetic field vertically through the windings in the winding region, this work introduces a structure that maintains most of the magnetic flux parallel to the foil windings through the application of quasi-distributed air gaps. This paper presents a design methodology for a high-frequency foil winding inductor with high flux variation. Building on this concept, a high-power density, low loss inductor with foil windings is designed based on the four-switch buck-boost (FSBB) converter. Experimental results demonstrate that the proposed inductor design significantly reduces winding loss in inductors with planar windings. Full article

RFID (radio frequency identification) tags play a crucial role in a wide range of applications, from wireless communications to personal tracking and smart city infrastructure. These tags come in various shapes and sizes, prompting the authors to review the specialized literature and focus on optimizing planar designs with different geometries. This study prioritizes reducing the size of the most commonly used tags while enhancing their reliability. The primary objective of this article is to understand and improve the performance of planar RFID tags operating at 13.56 MHz through numerical simulations based on structures generated by algorithms developed in MATLAB. Building on previous research, the methodology is validated, followed by a detailed description of the algorithm designed and implemented by the authors in MATLAB to identify all possible structures that meet the design criteria. The authors compared various analyzed structures, considering different inductor shapes, dielectric materials, and thicknesses while examining their effects on gain and resonant frequency. The study also provides thermal analysis of the structures, and experimental validation of the studied designs. Finally, the researchers conclude with recommendations on the optimal structure for RFID tags. Full article

Planar magnetic components have been widely used in high-density power converters and are suitable for various topologies. The application of planar inductors in LLC resonant converters can lead to parasitic capacitance, which causes current ringing and results in EMI issues. To mitigate the impact of current ringing, the parasitic capacitance of the planar inductor needs to be reduced. This paper proposes a new six-turn interleaved winding design. Compared to the previous four-turn interleaved winding design, it maintains low parasitic capacitance while positioning both the input and output terminals of the inductor on the outer turn, further enhancing the integration of high-density power converters. The parasitic capacitance was calculated using theoretical methods and verified through finite element simulations. Experimental validation was conducted using an LLC resonant converter test platform. Compared to the previous four-turn interleaved winding design, the new six-turn interleaved winding design satisfies both the input and output terminals, using an outer turn configuration. Additionally, the new design exhibits reduced parasitic capacitance and is suitable for use in LLC resonant converters, where it also minimizes current ringing. Full article

Low-frequency working standards of inductance are generally uniformly wound toroids on a ceramic core. Planar inductors made using printed circuit board (PCB) technology are simple and cheap to manufacture in comparison to inductors wound on toroid cores, but they are significantly prone to the influence of external magnetic fields. In this paper, we propose the design of a PCB inductance working standard of 10 μH, consisting of a duplex system of planar PCB coils, electrostatic shielding, and an enclosure. Alongside an electromagnetic analysis and design procedure, the measurements on the manufactured prototype included the generated magnetic field, the thermal time constant of the enclosure, temperature coefficients, and its error analysis. The measurements show negligible generated magnetic fields (<$1.68\mathrm{n}\mathrm{T}\mathrm{a}\mathrm{t}7\mathrm{c}\mathrm{m}$, 49 mA, 10 kHz). The minimum thermal time constant of the enclosure is 1270 s and the temperature coefficient of resistance is $0.003841/℃$. The presented method of temperature coefficient measurement using a climate chamber allows for measurements in the temperature range of 10 °C to 40 °C. In this temperature range, the results show an inductance variation of 0.05 µH at 50 kHz, while the uncertainty of inductance measurement at this frequency was 0.03 µH (k = 2). Full article

Congestive heart failure (CHF) is a fatal disease with progressive severity and no cure; the heart’s inability to adequately pump blood leads to fluid accumulation and frequent hospital readmissions after initial treatments. Therefore, it is imperative to continuously monitor CHF patients during its early stages to slow its progression and enable timely medical interventions for optimal treatment. An increase in interstitial fluid pressure (IFP) is indicative of acute CHF exacerbation, making IFP a viable biomarker for predicting upcoming CHF if continuously monitored. In this paper, we present an inductor-capacitor (LC) sensor for subcutaneous wireless and continuous IFP monitoring. The sensor is composed of inexpensive planar copper coils defined by a simple craft cutter, which serves as both the inductor and capacitor. Because of its sensing mechanism, the sensor does not require batteries and can wirelessly transmit pressure information. The sensor has a low-profile form factor for subcutaneous implantation and can communicate with a readout device through 4 layers of skin (12.7 mm thick in total). With a soft silicone rubber as the dielectric material between the copper coils, the sensor demonstrates an average sensitivity as high as –8.03 MHz/mmHg during in vitro simulations. Full article

To enhance the power density of LLC resonant converters, multilayer planar inductors are required. However, multilayer planar inductors have high parasitic capacitance, which may cause inductor current ringing in LLC resonant converters, leading to EMI problems. In this paper, it is found that by using interleaved winding inductors, compared with traditional winding inductors, the parasitic capacitance of multilayer planar inductors is reduced, which can reduce current ringing, without sacrificing power density and increasing manufacturing complexity. The method used to analyze current ringing is to establish an impedance model, and the parasitic capacitance of the interleaved winding inductors is verified by FEM simulations. The analysis is validated in an LLC resonant converter prototype. Full article

The on-chip integration of a power inductor together with other power converter components of small sizes and high-saturation currents, while maintaining a desired or high inductance value, is here pursued. The use of soft magnetic cores increases inductance density but results in a reduced saturation current. This article presents a 3D physical model and a magnetic circuit model for an integrated on-chip power inductor (OPI) to double the saturation current using permanent magnet (PM) material. A ~50 nH, 7.5 A spiral permanent magnet on-chip power inductor (PMOI) is here designed, and a 3D physical model is then developed and simulated using the ANSYS^®/Maxwell^® software package (version 2017.1). The 3D physical model simulation results agree with the presented magnetic circuit model, and show that in the example PMOI design, the addition of the PM increases the saturation current of the OPI from 4 A to 7.5 A, while the size and inductance value remain unchanged. Full article

This paper investigates the effect of different designs and arrangements of conductors on the operational parameters of a planar inductor. Accordingly, it is suggested that there is no one-size-fits-all design that can achieve all desired parameters in every application, and the best design should be determined by the needs of the application. In order to have a comprehensive study, four different structures are considered and compared. Numerous design parameters such as track width, track length, location of the conductors between the central limb and the lateral limb, and number of transposition points among subtracks for both air-core and ferrite-core inductors are considered. Each structure is evaluated according to AC resistance, $R_{AC}/R_{DC}$, and inductance. Measurement results reveal that it is critical to take into account all three characteristics when deciding the suitable structure for the conductors. Studies are carried out based on measurement results for experimental prototypes in the frequency range of 10 Hz–1 MHz, and a set of guidelines is provided with regard to the design of planar inductors to achieve desired characteristics. Full article