Variation Of Coupling Coefficient Research Articles

Strain partitioning along the western margin of North America

This paper describes an elastic block model for the interseismic horizontal crustal velocity field occurring in that part of the United States located west of longitude 100° W and between latitudes 31°N and 49°N. We developed the model by simultaneously inverting 6873 GPS-derived velocity vectors and 166 geological fault slip rates for the angular velocities (i.e. the Euler poles relative to the North America plate) of 46 elastic blocks, horizontal strain rate tensors for 38 of these blocks, and the spatially variable elastic coupling coefficients on faults that bound adjacent blocks.While the model covers all of the western United States located between Canada and Mexico, this paper focuses on the region residing south of Cape Mendocino where plate boundary deformation is accommodated predominantly by slip on the San Andreas fault system. Block strain rates (which account for deformation associated with distributed faults within blocks) are systematically higher in blocks located in the western part of the model and adjacent to the plate boundary. Strain rate magnitudes range from over 10−7/yr for some blocks adjacent to the San Andreas fault system to values of about 10−9/yr for blocks located in eastern Nevada and western Utah. Blocks adjacent to the San Andreas fault system are characterized by strain rate tensors that correspond to uniaxial contraction perpendicular to the local strike of the San Andreas. The highest rates of fault normal contraction are associated with the northern end of the fault (north of San Francisco) and in the southern end (south of Los Angeles). The central San Andreas (including the creeping segment of the fault) is characterized by strain rate tensors more consistent with dextral shear. Thus the northern and southern ends of the fault are consistent with a transpressional strain partitioning model with strike slip occurring on the San Andreas fault system and distributed shortening occurring within the blocks adjacent to this fault system. There is no evidence of strain partitioning in the central San Andreas.

Feedback control of TET system with variable coupling coefficients for a novel artificial anal sphincter

For treating severe faecal incontinence, the authors developed an intelligent artificial anal sphincter system (AASS) equipped with a feedback sensor that utilized a transcutaneous energy transfer system (TETS). To deliver the correct amount of power (i.e. to match the load demand under variable coupling conditions caused by changes in positioning between the coils due to fitting and changes in posture), a regulating method to stabilize output voltage with a closed loop variable-frequency controller was developed in this paper. The method via which the voltage gain characteristics of a voltage-fed series-tuned TETS were derived is also described. The theoretical analysis was verified by the results of the experiment. A numerical analysis method was used as a control rule with respect to the relationship between operating frequency and output voltage. To validate the feedback control rules, a prototype of the TET charging system was constructed, and its performance was validated with the coupling variation between 0.12–0.42. The results show that the output voltage of the secondary side can be maintained at a constant 7 V across the whole coupling coefficient range, with a switching frequency regulation range of 271.4–320.5 kHz, and the proposed controller has reached a maximal end-to-end power efficiency of 67.5% at 1 W.

Propagation and perfect transmission in three-waveguide axially varying couplers

We study a class of three-waveguide axially varying structures whose dynamics are described by the su(3) algebra. Their analytic propagator can be found based on the corresponding Lie group generators. In particular, we show that the field propagator corresponding to three-waveguide structures that have arbitrarily varying coupling coefficients and identical refractive indices is associated with the orbital angular momentum algebra. The conditions necessary to achieve perfect transmission from the first to the last waveguide element are obtained and particular cases are elucidated analytically.

An Electrically Tunable Liquid Crystal Lens for Fiber Coupling and Variable Optical Attenuation

An electrically tunable Liquid Crystal (LC) lens for both of fiber coupling and variable optical attenuation is demonstrated. The LC lens modulates the beam waist coupling to the fiber by electrically changing the lens power. When the modulated beam waist is close to the core size of the fiber, the LC lens is operated as a lens coupler. When the beam waist increases by reducing the lens power, the LC lens is operated as a Variable Optical Attenuator (VOA) as a result of the corresponding coupling coefficient variation of the transformed beam into a multimode fiber. The study provides a way to design an optical device for fiber coupling and variable optical attenuation based on electrically tunable focusing optical component.

Fast and Robust Beam Coupling in a Three Waveguide Directional Coupler

We propose fast and robust beam coupling in a three waveguide directional coupler based on Lewis-Riesenfeld invariant theory. This method provides shortcuts to optical waveguide couplers based on coherent tunneling adiabatic passage of photons. The design and performance of directional couplers using the invariant-based inverse engineering are discussed. Beam coupling is achieved by engineering the evolution of the eigenmodes of the invariant. We show that the invariant-based inverse engineering scheme reduces coupler length as compared with the common adiabatic scheme. The device is robust against coupling coefficient variations and has broadband characteristics.

A tunable dual-passband filter based on improved ring resonator

A miniaturized varactor-tuned microstrip bandpass filter (BPF) based on an improved ring resonator is presented in this paper. The proposed BPF is comprised of a ring as 1/2 λ resonator with two varactors in the middle section and a coupling scheme. The variation of coupling coefficient can be controlled by using a capacitor. The center frequency of the lower passband can be tuned from 3.2 to 3.9 GHz, while the center frequency of the upper passband is at 4.9 GHz and it is fixed during the process. Theoretical analysis and design approach are demonstrated. Finally, the predicted results are compared with measured data and good agreement is reported.

An investigation of novel capacitor-based coupling scheme and its applications to microstrip bandpass filters

In this paper, we present a novel capacitor-based coupling scheme for realizing both harmonic-suppressed and miniaturized microstrip bandpass filters. The proposed coupling scheme employs lumped-/distributed-capacitors to provide the desired coupling strength between the resonance elements instead of traditional parallel-coupled lines. Certain coupling regions are replaced by coupling points resulting in high freedom degree of the filter topologies. Thus, the filter structure can be effectively miniaturized by meandering microstrip lines. To investigate the properties of the novel coupling scheme, an analytical equation is derived for describing the coupling coefficient variation vs. the positions of coupling points and the values of coupled-capacitors. Theoretical analysis indicates that several zero-voltage points can be chosen to suppress the harmonics, and the coupling coefficient can be easily tuned in a wide range by adjusting the capacitance of the coupled-capacitor. For demonstration, two sample filters are designed and fabricated. Simulation and experimental results agree well, validating the proposed methodologies.

Nonreciprocal behavior and switching in optical couplers with longitudinally varying coupling coefficient

We report the nonreciprocal behavior of an optical coupler consisting of two straight waveguides forming a small angle. An optical diode action is theoretically demonstrated when light is launched along opposite directions. The switching power is lower than the case of parallel waveguides with a constant coupling coefficient.

Thermal stability analysis of nonlinear optical switch based on asymmetric three-core nonlinear directional coupler with variable Gaussian coupling coefficient

We analyze the thermal stability of the power transmission efficiency and the extinction ratio in an asymmetric three-core silicon-on- insulator nonlinear directional coupler with variable Gaussian coupling coefficient. Because the refractive indices of Si and SiO2 materials are subject to temperature change, the effective refractive index of the non- linear coupler varies correspondingly. When ratio (LC/b) andT change, the relative transmission efficiency error (� ) values and relative change of extinction ratio (η) values are obtained. It can be easily shown that vari- ation ofand η are negligible under LC/b ≤ 1/2. Therefore, we can set LC/b ≤ 1/2 andT ∈ (-100 K, 100 K) in order to make the power transmis- sion efficiency and the extinction ratio work steadily. This is significant in guiding an actual nonlinear optical pulse switch fabrication. C � 2011 Society

A 0.6-V 0.33-mW 5.5-GHz Receiver Front-End Using Resonator Coupling Technique

In this study, a low-power and low-voltage 5.5-GHz receiver front-end circuit is designed using a resonator coupling technique. An on-chip transformer combined with the parasitic capacitances from a low-noise amplifier (LNA), a mixer, and the transformer itself comprises two coupled resonators of the resonator coupling network (RCN). The RCN functions as a balun, and couples energy from the LNA to the mixer. Under the critical coupling condition, the RCN gives a maximal current gain at resonance frequencies, equivalent to the same level by an ideal transformer. The analysis shows that the current gain is quite tolerable to the coupling coefficient variation, an advantageous feature for on-chip transformer design. The technique is verified by the receiver front-end in 0.18-μm CMOS technology. The RCN possess a current gain as high as 12 dB at 5.5 GHz. The measured input return loss, conversion gain, and third-order intermodulation intercept point of the entire circuit are 16 dB, 17.4 dB, and -1.5 dBm, respectively. The noise figure is 7.8 dB at the IF frequency of 1 MHz. The power consumption is only 0.33 mW from a 0.6-V supply. The required local oscillator power is only -9.5 dBm. This receiver front-end successfully demonstrates the resonator coupling technique.

Cellular polypropylene polymer foam as air-coupled ultrasonic transducer materials

Cellular polypropylene polymer foams, also known as ferroelectrets, are compelling candidates for air-coupled ultrasonic transducer materials because of their excellent acoustic impedance match to air and because they have a piezoelectric d(33) coefficient superior to that of PVDF. This study investigates the performance of ferroelectret transducers in the generation and reception of ultrasonic waves in air. As previous studies have noted, the piezoelectric coupling coefficients of these foams depend on the number, size, and distribution of charged voids in the microstructure. The present work studies the influence of these parameters both theoretically and experimentally. First, a three-dimensional model is employed to explain the variation of piezoelectric coupling coefficients, elastic stiffness, and dielectric permittivity as a function of void fraction based on void-scale physics and void geometry. Laser Doppler vibrometer (LDV) measurements of the effective d(33) coefficient of a specially fabricated prototype transmitting transducer are then shown which clearly indicate that the charged voids in the ferroelectret material are randomly distributed in the plane of the foam. The frequency-dependent dynamic d(33) coefficient is then reported from 50 to 500 kHz for different excitation voltages and shown to be largely insensitive to drive voltage. Lastly, two ferroelectret transducers are operated in transmit-receive mode and the received signal is shown to accurately represent the corresponding signal generated by the transmitting transducer as measured using LDV.

Feedback analysis and design of inductive power links driven by Class-E amplifiers with variable coupling coefficients

The efficiency of inductive power links driven by Class-E amplifiers may deteriorate due to variation in the coupling coefficient when the relative position of the radio frequency (RF) coils changes. To solve this problem, a new design methodology of power links is presented in this paper. The aim of the new design is to use the feedback signal, which is a phase difference between the driving signal and the output current of the Class-E amplifier, to adjust the duty cycle and angular frequency of the driving signal to maintain the optimum state of the inductive power link, and to adjust the supply voltage to keep the output power constant when the coupling coefficient of the RF coils changes. The parameter adjustments with respect to the coupling coefficient and the feedback signal are derived from the design equation of the inductive power link. To validate the feedback control rules, a prototype of the inductive power link was constructed, and its performance validated with the coupling coefficient set at 0.2 and a duty cycle of 0.5. The experimental results showed that, by adjusting the duty cycle, the angular frequency, and the supply voltage, the power link can be kept in optimal operation with a constant output power when the coupling coefficient changes from 0.2 to 0.1 to 0.25.

공기 매질에 의한 압전 세라믹스의 분극효과

A new method for the poling of piezoelectric ceramics with an air insulation medium in stead of silicon oil is described. A similar variation of electromechanical coupling coefficient <TEX>$K_t$</TEX>, for an air medium is observed in comparison to that of the material poled by the conventional poling method using a silicon oil medium. Different poling parameters such as dielectric constant <TEX>$\varepsilon^T$</TEX> and frequency deviation <TEX>${\Delta}f$</TEX> are studied as well as the influence on the aging effect. The required poling factors to achieve the optimal piezoelectric characteristics are electric field, 2 kV/mm, temperature <TEX>$100^{\circ}C$</TEX>, and poling time 30 Min. From this result electric field 3 kV/mm atmosphere airs there being will be able to use with the polarization insulation medium about the piezoelectric material, confirmed.

Low-Loss Frequency-Agile Bandpass Filters With Controllable Bandwidth and Suppressed Second Harmonic

This paper presents a novel approach to design frequency-agile bandpass filters with constant absolute bandwidth and passband shape, as well as a suppressed second harmonic. A novel mixed electric and magnetic coupling scheme is proposed to control the coupling coefficient variation. Theoretical analysis indicates that it is able to achieve desired coupling coefficients between the proposed resonators at various frequencies so as to obtain constant absolute bandwidth. Moreover, this half-wavelength resonator has a Q higher than the quarter- and half-wavelength counterparts, thus resulting in low insertion loss. A filter of this type is designed to validate the proposed idea. To remove the spurious responses of the filter, a method is then introduced to suppress the second harmonic without degrading the passband performance. For demonstration, two frequency-agile filters with 60- and 80-MHz constant absolute bandwidth are implemented with the frequency tuning range from 680 to 1000 MHz. Comparisons of experimental and simulated results are presented to verify the theoretical predications.

가변 임피던스 정합 회로를 갖는 루프 안테나를 이용한 13.56 MHz 무선 전력 전송 시스템

In this paper, we proposed a 13.56 MHz wireless power transfer system using loop antennas with tunable impedance matching circuits. In general, a wireless power transfer system shows an impedance mismatching due to a reflected impedance, because a coupling coefficient is varied with respect to separation distance between two resonating antennas. The proposed system can compensate the effect of this impedance mismatch owing to tunable impedance matching circuits using varactor diodes. Therefore, transmission efficiency is enhanced, moreover, the center frequency of the system is not changed, regardless of separation distance between two antennas. In order to demonstrate the performance of the proposed system, a wireless power transfer system with tunable impedance matching circuits is designed and implemented, which has a pair of loop antennas with a dimension of cm. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to a distance between loop antennas were measured. From measured results, the proposed system shows enhanced performances than the case of the general fixed impedance matching circuits. Therefore, we verified that the proposed wireless power transfer system using the proposed impedance matching scheme will be able to ensure robust operation even when the separation distance of antennas is varied.

루프 안테나를 이용한 무선 전력 전송 시스템의 새로운 설계법

본 논문에서는 가전기기 등에 무선으로 전력을 전송하는 것을 목표로 루프 안테나를 이용한 무선 전력 전송 시스템의 새로운 설계 방법을 제안하였다. 본 설계 방법은 복잡한 전자기 시뮬레이션 없이 간단한 결합 계수의 측정과 루프 안테나의 등가 회로 모델에 대한 근사식만으로 무선 전력 전송 시스템을 설계할 수 있다. 본 논문에서 제시한 설계 방법에 따라 13.56 MHz에서 동작하는 <TEX>$50{\times}50\;cm^2$</TEX> 크기를 갖는 루프 안테나 쌍을 설계하고, 거리에 따른 입력 반사 계수, 결합 계수, 효율 및 임피던스 변화를 측정하였다. 측정 결과, 본 논문에서 제안한 설계 방법이 입력 임피던스 특성을 정확하게 예측할 수 있음을 확인하였다. 또한 50 cm 이하의 거리에서 본 논문의 설계 방법을 이용하여 임피던스 정합한 무선 전력 전송 시스템이 일반적인 <TEX>$50\;{\Omega}$</TEX> 임피던스 정합 회로를 갖도록 설계된 경우보다 효율이 2배 정도 개선되는 것을 확인하여 제안한 설계법의 유용성을 확인하였다. In this paper, we propose a new design method to design a wireless power transfer system using loop antennas for consumer electronics. This method can simply design a wireless power transfer system only using measurements of coupling coefficients and simple equations of equivalent circuit model about loop antennas without complicated electromagnetic analysis. Using the proposed design method, a wireless power transfer system with a pair of loop antennas operating at the frequency of 13.56 MHz, which have a dimension of <TEX>$50{\times}50\;cm^2$</TEX>, is designed and implemented. The input return loss, coupling coefficient, efficiency, and input impedance variation with respect to a distance between loop antennas were measured. The proposed design method provides good agreements between measured and predicted results. Also, the wireless power transfer system with impedance matching circuits designed by the proposed design method shows two times higher efficiency characteristics than the case with the general <TEX>$50\;{\Omega}$</TEX> impedance matching circuits. Therefore, we verified that our design method could be an effective tool to design a wireless power transfer system.

Analytic sensitivity calculations of poles and zeros of general Chebyshev filtering functions for microwave coupled resonators

A methodology for calculating the sensitivity of filtering poles and reflection zeros in coupled resonator structures is presented. Rather than finding the sensitivity of the S-parameters across a given frequency spectrum, the proposed method allows for calculating the sensitivity of each pole and zero with respect to coupling coefficient variations. This provides a better insight into the effects of fabrication tolerance on the filtering response and could lend itself to a more systematic approach to tuning. A detailed numeric example is provided for an asymmetric fourth-order Chebyshev filter.

Steady state analysis of optical bistability in distributed coupling coefficient DFB semiconductor laser amplifiers

In this paper, optical bistability behavior in a distributed feedback (DFB) semiconductor laser amplifier (SLA), with nonuniform-grating is studied. The investigation is focused on distributed coupling coefficient (DCC) structures, in which the corrugation has a nonuniform depth along the cavity. A modified implementation of transfer-matrix method, which takes the longitudinal variation of coupling coefficient along the structure into account, and considers gain saturation, is utilized to examine switching characteristics of DCC DFB SLA’s in the steady state regime. Along with the wavelength dependence of bistability hysteresis, the structural dependence of switching performance in these devices is demonstrated. Low-power switching spectral range and ON–OFF contrast ratio is investigated and the results are discussed.

Coupling coefficients evaluation of a directional coupler using gain guided and index antiguided fibers

In this paper, we have investigated the mutual and self coupling characteristics of directional couplers using two individual gain guided and index antiguided fibers, which can deliver robust single mode operation with large mode area, respectively owing to the combined adequately large gain coefficients in the core; Some interesting and distinguishing properties from conventional index guided fiber couplers are obtained that: The variations of coupling coefficients are complex-valued and spatially damping oscillated, but not exponential-like decreasing as conventional index guided couplers.

Integrated III–V Bragg Gratings for Arbitrary Control Over Chirp and Coupling Coefficient

In this work, integrated chirped Bragg gratings based on tapered waveguide sidewall gratings are presented, along with the method by which arbitrary variations of Bragg condition and coupling coefficient may be achieved. Fabricated devices with constant Bragg condition, linear, and nonlinear chirp are exhibited with and without apodized coupling coefficient profiles. Finally, an integrated Michelson interferometer setup is used to confirm the grating phase characteristics.