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Meander Line Antenna (MLA) is widely employed in compact electronic devices, such as cellular phones and WLAN terminals, owing to its electrically small size. To facilitate practical antenna design, essential equations encompassing self-resonant structure, input resistance, antenna efficiency, and Q factor have been systematically developed. However, the prior self-resonant equations included only inductive reactance (XC), neglecting the capacitive reactance (XD) equation. This manuscript addresses this gap by introducing new design equations, presenting a newly derived $\rm X_{D}$ equation and an improved Q factor expression. The inadequacies of the existing Q factor equation, reliant on the radius of a sphere encompassing the antenna, are addressed by proposing a more fitting expression that incorporates antenna structural parameters using the ratio of reactance to resistance. The overview of existing design equations sets the stage for the introduction of these newly developed equations. To assess the accuracy of electromagnetic (EM) simulation results, a comparative analysis is conducted between simulated and theoretically calculated input resistance values. The derivation of new reactance equations involves the development of $\rm X_{C}$ equations based on electromagnetic theory. The $\rm X_{D}$ equation is established by deriving the stored charge equation from electrical near-field distributions obtained through EM simulations. By applying the relationship between charge and capacitance, a new $\rm X_{D}$ equation is obtained. Subsequently, a new self-resonant equation is derived, and the validity of the newly derived equations is confirmed through EM simulation results, ensuring their accuracy. Two MLA prototypes, with lengths of 0.05 and 0.1 wavelengths at 405 MHz, are fabricated and experimentally validated. Smith chart measurements confirm the self-resonant condition and input resistance. By correlating with the VSWR characteristics, the obtained Q factor of approximately 100 aligns successfully with the results from the reactance equation. The antenna gain is verified at −7.7 dBi and −3.5 dBi for antennas with lengths of 0.05 and 0.1 wavelengths, respectively. These findings establish the practical applicability of the proposed equations for antenna design and elucidate the performance of practical antennas.

This paper presents a wireless power transfer (WPT) technique based on self-resonant Conformal Strongly Coupled Magnetic Resonance (CSCMR) model. The proposed model is compared to a capacitor-loaded mode in terms of their transmission efficiency through simulations. The simulations are run using MATLAB, High Frequency Structure Simulator (HFSS) and OptiSLang. Results confirm that a self-resonant CSCMR-WPT performs better than a capacitor loaded model. To achieve an efficient WPT, a lot of resources may be required for the model which necessitates a high computational time. Hence, compared to using only a 3D simulation software as reported in many literature, a co-simulation is performed between HFSS and OptiSLang to reduce computational resources. Furthermore, using MATLAB to conceptualise the CSCMR resonators gives better guidance and satisfactory results which shortens the simulation times by providing estimated WPT system parameters for an optimal model. The study concludes that, using the co-simulation has reduced computational time by 93% compared to only using the full-wave electromagnetic simulation (HFSS) which translates to quicker design time of WPT.

The resistance and inductance of an inductor working at high frequencies depend on frequency because of eddy currents caused by the skin and proximity effects. In addition, the stray capacitance among winding coils would give significant influence. This paper proposes an equivalent circuit model which can consider the displacement and eddy currents simultaneously in frequency and time domain. In the proposed circuit model, the capacitance and complex inductance are determined by solving electrostatic and magnetostatic equations with finite element method (FEM). It is shown that the input impedance of an air-core coil is consistent with that computed by FEM at low frequencies. Moreover, the former is shown to be consistent with the measured result. [ABSTRACT FROM AUTHOR]

This article proposed an underwater simultaneous wireless power transfer and data transfer system for the autonomous underwater vehicle. The double-sided LLCC compensation topology is proposed to effectively suppress the interference to the data channel at switching instant. With the increase of the size and turns of the coupling coils, the self-resonance frequency gradually decreases. However, the frequency of data carriers is usually much lower than the self-resonant frequency, which will reduce the data rate or improve the bit error rate at a high data rate. Moreover, the high voltage generated by coupling coils causes high voltage stress on the data channel. To deal with these two issues, the last turn of each coupling coil is used to transfer data in the proposed system. The two transceivers are, respectively, connected with the last turn of the two coupling coils, which excites the entire coils to self-resonate and generates two resonant frequencies. The two resonant frequencies are utilized to realize high-speed full-duplex communication. And the voltage stress of the data channel is effectively reduced. A 518-W full-duplex prototype is built, and the maximum data rate is 700 kb/s, which verifies the feasibility of the proposed system. [ABSTRACT FROM AUTHOR]

With the rapid development of wireless power transfer (WPT), the self-resonant WPT system without using additional compensation capacitors has attracted attention. However, most of reported self-resonant WPT systems have low power transfer (less than 100 W) and high operating frequencies at megahertz. In this article, four multilayer, self-resonant WPT coil pads with different dielectrics are designed and experimentally validated. The aim of this article is to increase the power rating and decrease the operating frequency for capacitor-free WPT system compared to reported systems used in consumer electronics. Analysis of integrated compensation capacitance, inductance, and parasitic capacitance of the coil is provided. Finite-element analysis is used to evaluate four dielectric materials, mica, polypropylene, polyimide, and fiberglass. An experimental setup has been developed, which can achieve more than 360-W power transfer for a 120 mm air gap with an efficiency of 82% and an operating frequency of near 80 kHz. [ABSTRACT FROM AUTHOR]

The self-adaptive behavior of a clamped–clamped beam with an attached slider has been experimentally demonstrated by several research groups. In a wide range of excitation frequencies, the system shows its signature move: The slider first slowly moves away from the beam's center, at a certain point the vibrations jump to a high level, then the slider slowly moves back toward the center and stops at some point, while the system further increases its high vibration level. In our previous work, we explained the unexpected movement of the slider away from the beam's vibration antinode at the center by the unilateral and frictional contact interactions permitted via a small clearance between slider and beam. However, this model did not predict the signature move correctly. In simulations, the vibration level did not increase significantly and the slider did not turn around. In the present work, we explain, for the first time, the complete signature move. We show that the timescales of vibration and slider movement along the beam are well separated, such that the adaptive system closely follows the periodic vibration response obtained for axially fixed slider. We demonstrate that the beam's geometric stiffening nonlinearity, which we neglected in our previous work, is of utmost importance for the vibration levels encountered in the experiments. This stiffening nonlinearity leads to coexisting periodic vibration responses and to a turning point bifurcation with respect to the slider position. We associate the experimentally observed jump phenomenon to this turning point and explain why the slider moves back toward the center and stops at some point. [ABSTRACT FROM AUTHOR]

A size reduction technique of non-planar and planar antennas using a self-resonant topology is highlighted. The antennas considered are the dipole, the monopole and the slot radiator. The dipole below its resonant frequency is known to possess a capacitive reactance. It is shown that the inductive reactance of a loop can be used to match a below-resonant dipole similar to the inductive load offered by a metamaterial shell. The configuration reduces the resonant frequency of the dipole by 26.01%, causing the dipole to almost reach the electrically small limit. Despite the loaded dipole touching the electrically small limit, the antenna needs no matching networks, offers a high efficiency and exhibits a bandwidth better than the unperturbed dipole. The radiation pattern is also seen to be unaffected by the presence of the loops. The concept is also demonstrated for the size-reduction of a monopole and for a planar slot. [ABSTRACT FROM AUTHOR]