Capacitive Coupling Coefficients Research Articles

A robust parity‐time‐symmetric hybrid wireless power transfer system with extended coupling range

SummaryInductive power transmission (IPT) and capacitive power transmission (CPT) are currently the two main wireless power transfer technologies. Hybrid power transmission (HPT) systems that combine IPT and CPT can improve transmission performance and are more attractive for some charging applications such as electric bicycles (e‐bikes). However, HPT systems are more sensitive to parameter variations, and the coupling mechanism is prone to misalignment during wireless charging. Therefore, achieving stable output power and constant transfer efficiency over a wide range of coupling coefficient variations is still a major challenge for HPT systems. In this work, the parity–time (PT) symmetry theory is applied to an SS‐type HPT system, and a circuit model of the PT‐based HPT system is developed by using coupling capacitance and coupling inductance. The effect of connecting the plates to the homonymous end or heteronymous end of the coupling coils on the PT symmetry range of the HPT system is discussed. It is found that the heteronymous end connection of the coils can effectively increase the range of constant output power and stable transfer efficiency. Finally, a prototype is built to verify the feasibility and effectiveness of the proposed PT‐based HPT system. The transfer power and efficiency remain constant in the PT‐symmetric range, and the inductive and capacitive coupling coefficients are smaller compared to IPT and CPT systems with the same parameters.

Vibration energy harvester of high-speed track slab foundation excitation

The vibration energy of the track slab can be converted into electric energy for wireless sensors by piezoelectric energy harvesters. A track laminated circular plate harvester (TLCP harvester) is designed in this paper based on foundation excitation. The central frequency of the harvester is 222 Hz, which is matched with the 222.8 Hz of the track slab. The stiffness curve, damping, equivalent capacitance, and electromechanical coupling coefficient of the harvester are obtained through the experiment. The harmonic balance method and Runge–Kutta’s voltage results are consistent with the experimental results. The frequency responses verify the jump phenomenon and soft characteristics. The experiment results show that the maximum output power is 8.07 mW under 7 kΩ load resistance, and the maximum RMS power is 0.3804 mW under 5 kΩ load resistance. This paper develops a safe and high-efficiency piezoelectric energy harvester for track slabs.

Crosstalk Reduction on Delay Line with Rectangular-Patches (RPs) Design

In this paper, a novel helix delay line with RPs structures is proposed to investigate the performance of crosstalk reduction. In the past, conventional delay lines consist of equal-length parallel unit lines which are closely packed to minimize the fabricated cost and routing area. All spacing between the adjacent parallel unit lines of delay lines should be smaller. When the operating signal frequency ups to the GHz level, the electromagnetic noise has become a dominant issue coupling from adjacent lines. It is called as a crosstalk source. The crosstalk may affect system-level timing. Besides, it causes error switching of logic gates that will reduce the signal quality. The feature of proposed helix delay line is that the far-end crosstalk (FEXT) is a dominated noise that accumulates at the receiving end. RPs structures are added and aligned at the center of the two parallel adjacent unit lines of the proposed helix delay line, which are used to reduce the difference between inductive and capacitive coupling coefficient ratios, and to reduce FEXT that maintains the signal integrity (SI) quality on receiving end.

Robust design optimization of a nonlinear monostable energy harvester with uncertainties

Based on the improved interval extension, a robust optimization method for nonlinear monostable energy harvesters with uncertainties is developed. In this method, the 2nd order terms in the interval extension formula of the objective function (output voltage) are kept so this approach is suitable for a nonlinear energy harvesting system. To illustrate this method, uncertain mass, uncertain capacitance and uncertain electromechanical coupling coefficient are optimized to maximize the central point of output voltage whose deviation of which is simultaneously minimized. Then, an optimal design with different robustness is obtained. The results also show that the robustness of the optimal design of nonlinear monostable energy harvesters is increased, but the cost of performance has to be paid for. Overall, the framework provides the optimal design for nonlinear energy harvesters (monostable, bistable, tristable, multistable harvesters).

Differential Bi-Level Microstrip Directional Coupler with Equalized Coupling Coefficients for Directivity Improvement

In this paper, a bi-level microstrip differential directional coupler has been investigated. It has been shown that the equalization of coupling coefficients can be successfully made with the use of appropriate dielectric stack-up and conductor geometry. The application of additional top dielectric layer can ensure proper equalization of coupling coefficients by lowering the value of capacitive coupling coefficient to the value of the inductive one. The theoretically investigated coupled-line section has been used for the design of a 3-dB differential directional coupler. The measurement results are compared with the theoretical ones.

An Improved LCL-L Compensation Topology for Capacitive Power Transfer in Electric Vehicle Charging

This paper proposes an LCL-L compensation circuit for high power capacitive power transfer (CPT) aiming at minimizing number of resonant components and improving system performance. The proposed topology adopts only four external resonant components at both sides of the capacitive coupler. The output power is proportional to the capacitive coupling coefficient, therefore, it simplifies the design procedure and abolishes protection circuit requirements under coupler’s misalignment. Moreover, optimizing efficiency at full-load conditions of compensation network can be easily achieved in this system by designing resonant components at the highest value of the mutual capacitance. Theoretical analysis of the proposed system is conducted alongside comparison to lasted CPT compensation circuits. Simulation and experimental results of a 1.5-kW CPT prototype with an air gap distance of 150 mm are provided to verify the feasibility and the effectiveness of the proposed system. System performances under different coupler’s misalignment conditions and output power levels are also examined and discussed as well.

Realization of High-Performance Broadband Quadrature Directional Couplers in UMS PH25 Technology

The problem of the realization of broadband quadrature directional couplers in UMS (United Monolithic Semiconductors) PH25 is thoroughly investigated. The limitations of the selected technology are discussed with respect to directional couplers’ design. It is shown that, in such technologies, two major problems have to be overcome to achieve the high-performance of the resulting integrated couplers, i.e., the realization of appropriate coupling together with appropriate characteristic impedances, and the equalization of inductive and capacitive coupling coefficients that are inherently different in inhomogeneous dielectric structures. Three different solutions that allow for achieving strong coupling in the selected UMS PH25 process were selected and experimentally investigated, showing the possibility of such circuits’ realization. In each of the presented integrated couplers, capacitive compensation techniques were applied for coupling coefficients’ equalization.

High‐performance differentially fed coupled‐line directional couplers realised in inhomogeneous medium

In this study, a generalised approach for the design of high-performance differentially fed coupled-line directional couplers in inhomogeneous medium is presented for the first time. Conditions for the realisation of ideal coupled-line section under differential excitation are provided and it is shown that generally in such medium couplers feature different capacitive and inductive coupling coefficients, which significantly deteriorate circuits' performance. Therefore, the compensation technique is proposed allowing for equalisation of the differential coupling coefficients by adding appropriate compensating elements to the per-unit-length capacitance and inductance matrices of the coupled-line section. The proposed approach allows for realisation of quasi-ideal differential coupled-line couplers designed in arbitrarily chosen dielectric stack-up, and almost for arbitrarily chosen coupling. The provided theoretical analysis and resulting design methodology are verified experimentally with a 3-dB differential coupler operating at f 0 = 1.5 GHz and realised in suspended microstrip technique. Moreover, a combination of laminate and additive manufacturing technologies was used for higher design flexibility and low-cost manufacturing.

Uncertainty Analysis of Bistable Vibration Energy Harvesters Based on the Improved Interval Extension

PurposeHigh-energy interwell oscillations of the bistable energy harvester (BEH) lead to large-amplitude output voltage. For processing and manufacturing of the BEH, small errors and deviations in the final structure cannot be totally eliminated in practice, which will make the output voltage to be apart away from the design value. Therefore, the geometrical variables, material properties and other parameters should be treated as uncertainties in analysis and are bound to their design.MethodThis paper presents uncertainty analysis of the BEH to reveal the influence of the uncertain system parameters on the energy harvesting performance. The improved interval extension based on the first-order Taylor series is used to predict the lower and upper bounds of the stable high-energy interwell output voltage of the BEH. In detail, uncertain mass, nonlinear stiffness term, damping, capacitance and electromechanical coupling coefficient are considered. Meanwhile, the Monte Carlo simulation is employed to verify the suitability and the accuracy of this method. Especially, this method allows researchers to define the number of the parameter αj according to the categories of uncertain variables.ResultsThe research works show that interval of the output voltage of the BEH can be limited by reducing the number of uncertain variables, and the uncertainty of the output voltage is more sensitive to the electrical uncertain variables than the structural uncertainties.ConclusionDesigners of the BEH should pay enough attention to the errors and tolerances of the electrical output design variables. Specifically, in the design of the BEH, it is more effective to improve the accuracy of the output voltage by limiting the uncertainties of electric parameters than structural parameters. Reducing the number of uncertain parameters through increasing processing precision in production of the BEH can also improve the accuracy of the output voltage.

Band Pass Filters Based on GaN/Si Lumped-Element SAW Resonators Operating at Frequencies Above 5 GHz

This paper reports on a GaN/Si surface acoustic wave (SAW) impedance element filter operating in the few gigahertz region. The PI-type filter consists of three SAW resonators with the same digit/interdigit widths, integrated with series/parallel planar inductors. The design procedure is based on modeling the SAW resonators using four parameters, independent of the equivalent circuit model representation (series resonance frequency, static capacitance, quality factor, and effective coupling coefficient). The series frequency is tuned by a planar inductor placed in series, while the parallel resonant frequency is tuned by a planar inductor placed in parallel with the SAW resonator. Closed-form equations are derived for the analysis of lumped-element SAW resonators. The design procedure is further based on the area of the SAW resonator and the lengths of the planar inductors as independent variables. Full-wave electromagnetic and circuital co-simulations and parametric optimizations are employed for the final filter design, which is implemented in the coplanar waveguide topology. The lumped-element SAW bandpass filter is fabricated using e-beam lithography for the definition of the 200-nm-wide interdigital transducers. Measurement results show the insertion losses of 12.9 dB at 5.49 GHz, the return losses of 16 dB, 3-dB bandwidth of 8.3 MHz, and the out-of-band rejection of 24 dB. The filter is compatible with monolithic integration with GaN active electronics.

Design of low-loss directional couplers with compensated coupled-line sections in suspended microstrip technique

Design of coupled line 3dB directional couplers realized in suspended microstrip technique has been presented. The main goal was to minimize the insertion losses of the coupler, what has been achieved by a proper choice of the realization technique. As the chosen coupled line geometry is asymmetric to achieve good electrical performance of the resulting coupler, capacitive compensation technique has been utilized to equalize capacitive and inductive coupling coefficients. Furthermore, a distributed-element approach has been investigated for realization of compensation capacitances, due to their physical size resulting from the dielectric structure. The proposed coupler has been designed in two versions, having center frequencies equal to 0.89 and 1.1 GHz, manufactured and measured. The measurement results show good agreement with electromagnetic analyses and prove the correctness and usefulness of the presented design method. The manufactured couplers exhibit insertion losses as low as 0.08 dB at the center frequency.

Defining the mutual coupling of capacitive power transfer for wireless power transfer

Capacitive power transfer (CPT) based on electric field coupling has been proposed recently as an alternative technology for wireless power transfer, and a good understanding of the capacitive coupling is of great importance in the design and evaluation of CPT systems. A new term named capacitive coupling coefficient kE is introduced to provide a quantitative measure of the coupling condition between the coupling plates. The term is derived by modelling the capacitive coupling plates based on electric charge balance, and its physical meaning is explained clearly in relation to the equivalent primary/secondary and mutual capacitances, which is also experimentally demonstrated by comparing two CPT systems with different cross-coupling configurations.

Numerical studies of the electromagnetic reciprocal influences of symmetric communication cable

The reciprocal influences between chains of symmetric communication cables is considered based on mathematical simulations of electromagnetic processes. It is assumed that the electric- and magnetic-field force lines are situated in the plane perpendicular to the cable axis and, therefore, the mathematical models describing the electric-potential distribution and components of the vector magnetic potential of alternating currents in a complex form can be presented in a two-dimensional setting. Differential equations written in the Cartesian coordinate system and describing the electric and magnetic potential distributions are solved by the finite-element method. The electromagnetic processes are studied numerically for the UTP Cat 5e LAN cable used in the structured cable networks. Such an approach allows one to determine electric- and magnetic-field distributions and calculate the coefficients of capacitive and inductive coupling in the cross section of a symmetric cable for a preset position of twisted pairs. The main way to reduce the reciprocal influences in unshielded symmetric communication cables is appropriate selection of twist pitches. The twist pitch in each chain should be chosen such that the integral of the capacitive and inductive coupling coefficients over a length of the symmetry section between all the cable chains tends to zero.

Voltage-Mode Multi-Valued Schmitt Trigger with Neuron-MOS Transistors

A novel design scheme of multiple-valued Schmitt trigger using neuron-MOS transistors is presented. By controlling the voltages of the multiple-input gates, the neuron-MOS literal circuits with hysteresis characteristics are firstly designed. Then, the transmission switches used to pass quaternary signal are controlled by the outputs of these literal circuits to realize three hysteresis loops of quaternary Schmitt circuit. The benefit of the proposed quaternary Schmitt trigger is that the circuit can be fabricated by standard CMOS process with a 2-ploy layer. The three hysteresis loops are fully adjustable by sizing the ratio of capacitive coupling coefficients. The effectiveness of the proposed Schmitt trigger has been validated by HSPICE simulation results with TSMC 0.35μm 2-ploy 4-metal CMOS technology, and the discrepancy of hysteresis values between the simulated and theoretical results is smaller than 6%.

Approach to the Design of Asymmetric Coupled-Line Directional Couplers With the Maximum Achievable Impedance-Transformation Ratio

A novel approach to the design of asymmetric coupled-line impedance-transforming directional couplers with the maximum achievable impedance-transformation ratio is proposed. It is shown that the couplers in which one conductor is completely shielded from the other can be represented by two uncoupled transmission lines, which significantly simplifies the design procedure. Furthermore, the proposed approach of the directional couplers' analysis has been utilized for the derivation of a general condition describing the maximum impedance transformation ratio that can be achieved for directional couplers designed in inhomogeneous media. It has been also shown that impedance-transforming directional couplers, in which the capacitive coupling coefficient differs from the inductive coupling coefficient feature limited isolation, and that such couplers can be represented by two uncoupled lines having different electrical lengths. Subsequently, it has been shown that this isolation can be improved when the electrical lengths of the two uncoupled lines are equal, which corresponds to the equalization of capacitive and inductive coupling coefficients. The theoretical analyses have been confirmed by the measurements of two different 3-dB impedance-transforming directional couplers designed with the use of the proposed simplified approach.

Generalized Methods for the Design of Quasi-Ideal Symmetric and Asymmetric Coupled-Line Sections and Directional Couplers

Generalized methods for the design of quasi-ideal symmetric and asymmetric coupled-line sections have been proposed. Two cases of coupled-line sections, in which the inductive coupling coefficient is either greater or smaller than the capacitive coupling coefficient, have been separately considered. To compensate for the coupling coefficients' inequality, a combination of lumped capacitors and short coupled-line sections has been introduced into the coupled-line section. The proposed methods allow for designing quasi-ideal coupled-line sections in nearly arbitrarily chosen dielectric media and for arbitrarily chosen coupling. The theoretical analyses have been verified by the design and measurement of three compensated coupled-line directional couplers illustrating application of the proposed methods in different dielectric structures.

Characterization of Short-Pulse Generation Using Traveling-Wave Field-Effect Transistors

Pulse propagation on traveling-wave field-effect transistors (TWFETs) is investigated for the generation of short pulses. In a properly designed TWFET, when a decreasing voltage pulse is applied to the gate line and an increasing one is simultaneously applied to the drain line, the pulses experience great shortening. Therefore, a TWFET operates as a short-pulse generator. In this paper, how the width of the finally obtained pulse depends on the device parameters, including the inductive and capacitive coupling coefficients between the gate and drain lines is clarified, and the design criteria of a TWFET as a pulse generator are described, together with several results of numerical calculations for examining its potential.

MoM Analysis and Design of a Compact Coaxial-to-Microstrip Directional Coupler

In order to overcome the main drawbacks of coaxial, waveguide, and stripline couplers, the analysis and the design of a compact coaxial-to-microstrip directional coupler convenient for power and antenna control application, are presented using the method of moments (MoM) in two dimensions. This technique is adapted to study the complex configuration of the line’s system, which does not have a simple analytical solution. The modeling of this structure consists in analyzing the primary inductive and capacitive matrices ([L] and [C]). When these matrices are determined, it is possible to calculate the inductive and capacitive coupling coefficients (kL and kC) and estimate the resulting scattering parameters of the coupler using an adapted numerical model. The coupler can be integrated into a printed circuit board (PCB) and operates over 17 to 35 dB coupling coefficients and is always compensated. The compensation is achieved by the proper displacement of a tuning ground plane with respect to the edge of the PCB from 0.1 to 3.3 mm. As an application, we present the design of a compact coupler with 7.5 × 4.8 × 25.8 mm of size and having approximately 20 dB of coupling coefficient at 2 GHz and a minimum directivity of 23.3 dB in the frequency range [0.1 - 4] GHz. In order to check our numerical calculations by the MoM we made simulations in 3D by using CST MICROWAVE STUDIO software for the same geometrical and physical parameters of our designed coupler. The results obtained by the two numerical models (MoM and CST) show a good agreement of the frequency responses of the coaxial-to-microstrip directional coupler. The studied structure represents a great improvement for high power measurement systems, since it has broad-band, good directivity, and can be easily designed and fabricated.

Investigation of Back-Bias Capacitance Coupling Coefficient Measurement Methodology for Floating-Gate Nonvolatile Memory Cells

In this paper, we give a thorough investigation of a new capacitance coupling coefficient measurement methodology (a back-bias method) that extracts the gate capacitance coefficient of floating-gate memory cells. This measurement methodology that utilizes simple current-voltage measurements presents several advantages over current methodologies. It includes a figure of merit for determining the matching performance of a reference transistor to a memory cell, which plays a crucial role for the extraction of the correct gate coupling coefficient value. By this means, we investigate, for the first time, the impact of structural differences between a reference transistor and a memory cell on the gate coupling coefficient extraction. The back-bias method is compared with commonly used gate coupling coefficient extraction methods, and it is shown that it has a smaller extraction error for nonmatching reference transistors and memory cell pairs. Furthermore, it is demonstrated how the gate coupling coefficient extraction can be corrected if matching reference and memory cell structures cannot be found.

Suspended stripline coupled lines with grounded strips for equalization of inductive and capacitive coupling coefficients

AbstractA suspended stripline coupled‐line structure has been proposed, which allows for achieving equalization of inductive and capacitive coupling coefficients in a wide range of directional couplers' coupling C. Three different variants of the proposed structure have been considered, and the results of numerical calculations using FD technique have been presented, which show the possibility of equalization of inductive and capacitive coupling coefficients. Moreover, graphs showing structural parameters are presented in a wide range of coupling coefficient k. The results of investigations have been confirmed by the measurements of the designed 15‐dB directional coupler. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:874–877, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25085