Desired Coupling Coefficient Research Articles

Design Methodology of Transmission-Line Quadruplet Filters Supported by Rigorous Circuit Transformations

This article presents a novel and rigorous technique to design transmission-line quadruplet filters. Unlike the prevailing approaches relying on electromagnetic (EM) simulations for coupling tests, the proposed design technique completely counts on rigorous circuit transformations. As all design parameters (lengths and line impedances) can be rigorously calculated from the design equations provided in this work, a quadruplet filter can be designed without conducting EM simulations to find the dimensions delivering the desired coupling coefficients. Our design approach will be demonstrated with the fourth-and fifth-order filter examples, both of which were fabricated and measured for validation.

Using Zone Impedance Matching Technique to Improve the Power Transfer Capability of an Inductive Charging System over a Long Distance

In many outdoor inductive charging applications, the objects can move quickly, and the environment can change unpredictably. It is therefore difficult to design a fast controller that tracks the change in mutual coupling between the transmitter and receiver. The diminished power delivery to the objects either leads to incomplete charging or prolongs the charging time. In this paper, the concept of a zone impedance matching technique is proposed. This technique pre-matches the transmitter coil to the desired coupling coefficients. Thus, the power transfer capability of the inductive charger can be maintained at a reasonably high level over a long transmission distance and under a wide receiver misalignment. Based on a three-coil inductive power transfer (IPT) system, the proposed concept is practically implemented with a simple control scheme. The proposed IPT system equips a multi-tap transmitter coil to provide flexibility in selecting different numbers of turns in the transmitter coil. The controller senses the currents of the transmitter coil and the repeater coil to determine the zone of impedance to adapt to the change in mutual coupling of the coils. A mathematical analysis is conducted to formulate the design procedures for the proposed system. Under a wide range of distance and misalignment conditions, practical measurement results verified that the proposed system achieves higher power delivery than an ordinary design.

Design of coupled inductors using split winding scheme for bridgeless SEPIC

A bridgeless single-ended primary inductance converter (SEPIC) is a highly preferred single-stage front-end AC–DC converter for applications requiring a wide variation of DC voltage because it also gives improved performance in terms of the quality of supply current. This study presents the design of coupled inductors for the bridgeless SEPIC using the split winding scheme. With coupling incorporated the required value of self-inductances of the input and output inductors for the same performance is reduced. Also, they can be wound on the same core, thereby resulting in a reduction in size. The conventional method of tuning the coupling coefficient by adjusting the air-gap is tedious. A split winding scheme for the distribution of windings over three limbs of E-core for obtaining the desired coupling coefficient is presented. The split winding scheme for the design of coupled inductors for bridgeless SEPIC converter rated for 500 W, 20 kHz is illustrated. The effect of coupling on the volume, weight, cost, and efficiency of the converter is compared with the conventional SEPIC converter without coupling for a similar performance. The performance of the proposed converter is evaluated using MATLAB/Simulink simulation and experimental results with a laboratory prototype rated for 500 W.

Compact Tunable Balanced Bandpass Filter With Constant Bandwidth Based on Magnetically Coupled Resonators

In this letter, a compact high-selectivity and common-mode (CM) suppression tunable balanced microstrip bandpass filter (BPF) with constant bandwidth is designed by adopting the magnetically coupled resonators with step-impedance parallel coupling feedline (SIPCF) structure. The desired coupling coefficient $K_{12}$ and external quality factor $Q_{e}$ can be obtained by the mixed coupling between the two resonators and SIPCF structure, respectively. Two differential-mode (DM) transmission zeros (TZs) near the lower and upper passband edges are created by the mixed coupling and source–load coupling, respectively. Furthermore, intrinsic high CM suppression in the DM tunable operating passband can be maintained because of the magnetically coupled resonator structure. Finally, a compact tunable balanced BPF prototype with constant fractional bandwidth of 6.5% is implemented and fabricated. The measured results agree well with the simulated ones.

Field tuning and rf measurements of the four-vane radio frequency quadrupole with ramped inter-vane voltage

This paper describes the physical design, rf measurement, and tuning result of a 325 MHz four-vane radio frequency quadrupole (RFQ) with a ramped inter-vane voltage. The 3-meter-long RFQ will accelerate the negative hydrogen ion beam from 50 keV to 3 MeV with a peak current of 5 mA, a pulse width of $10--40\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$, and a maximum repetition rate of 0.5 Hz. During tuning we reveal that the coupling loop of the coaxial coupler adopted for this RFQ enhances the interference between the dipole field distribution and the coupling coefficient. Therefore, an iteration method is adopted to simultaneously achieve the desired field distribution and coupling coefficient. After tuning, the relative error between the measured field distribution and the designed curve for the operating quadrupole mode is within $\ifmmode\pm\else\textpm\fi{}2.7%$, and the dipole components are about $\ifmmode\pm\else\textpm\fi{}1.9%$ of the quadrupole mode. The measured coupling coefficient of the rf power coupler equals 1.03, with the desired value of 1.04.

Compact reconfigurable bandpass filter with wide frequency tuning range

ABSTRACTA compact reconfigurable bandpass filter with wide tuning range is proposed in this letter. The reconfigurable function is realized by utilizing two varactor diodes at the end of the bandpass filter. Instead of using the coupling gap to create the desired coupling coefficients, a high characteristic impedance line is applied. A compact reconfigurable filter is designed, fabricated and measured. The measured tuning frequency ranges from 0.38 GHz to 0.96 GHz, which is about 86.6% of the central frequency. The measured insertion loss of the proposed reconfigurable filter is less than 2.5 dB, while the measured return loss is greater than 11 dB.

Compact dual‐band balanced bandpass filter based on double‐layer SIW structure

A compact dual-band balanced bandpass filter with high common-mode (CM) suppression is proposed. Two layers of substrate are vertically stacked to realise the miniaturisation. The first differential-mode passband can be obtained by the dominant modes and the second can be achieved by utilising the higher-order modes. The desired coupling coefficients of both bands are achievable by properly setting positions and sizes of the coupling slots etched on the layer interface. Meanwhile, four slotlines are etched on the bottom layer of the substrate to improve CM suppression and band-to-band isolation. A four-order prototype is designed for demonstration. Good agreement between simulated and measured results is obtained.

Study of the effect of loop inductance on the RF transmission line to cavity coupling coefficient.

Coupling of RF power is an important aspect in the design and development of RF accelerating structures. RF power coupling employing coupler loops has the advantage of tunability of β, the transmission line to cavity coupling coefficient. Analytical expressions available in literature for determination of size of the coupler loop using Faraday's law of induction show reasonably good agreement with experimentally measured values of β below critical coupling (β ≤ 1) but show large deviation with experimentally measured values and predictions by simulations for higher values of β. In actual accelerator application, many RF cavities need to be over-coupled with β > 1 for reasons of beam loading compensation, reduction of cavity filling time, etc. This paper discusses a modified analytical formulation by including the effect of loop inductance in the determination of loop size for any desired coupling coefficient. The analytical formulation shows good agreement with 3D simulations and with experimentally measured values. It has been successfully qualified by the design and development of power coupler loops for two 476 MHz pre-buncher RF cavities, which have successfully been conditioned at rated power levels using these coupler loops.

New Design of Waveguide Directional Coupler Using Genetic Algorithm

In this letter a novel design method for waveguide directional coupler is proposed based on genetic algorithm. Using the proposed method, a waveguide directional coupler with desired coupling coefficient ( $C$ ), has been designed, so that maximum mean value of directivity ( $D$ ) is achieved in the frequency range. In this method, a specified patterned aperture, which can be determined using genetic algorithm, couples power between two parallel waveguides. In order to extract specified pattern of coupling aperture, coupled magnetic field integral equation in term of surface magnetic current is derived and solved by method of moments to obtain general scattering matrix and then coupling coefficient and directivity of directional coupler are calculated. The proposed patterned aperture compared with conventional circular hole directional coupler of the same length, has been improved the mean value of directivity around to 137.7% for a given coupling coefficient. The performance of the proposed method is verified with the results of simulation. To validate the simulation results, a waveguide directional coupler using patterned aperture is designed, fabricated and measured.

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.

Dual-Band Vertically Stacked Laminated Waveguide Filter Design in LTCC Technology

A new design method of dual-band filters with laminated waveguide (or substrate integrated waveguide) is proposed by taking advantage of the existence of multiple cavity modes. The major design concept is adequately choosing geometric shape of laminated waveguide resonators to control the frequency bands, and positions of open slots and feeding probes to realize the desired coupling coefficients and external quality factors at both bands simultaneously. Two design examples with third-order and quasi-elliptic filter responses are given and verified by experiments. By using the low-temperature co-fired ceramic technology, the laminated waveguide resonators are vertically stacked, and the filter size can be miniaturized.

Method for controlling piezoelectric coupling coefficient in film bulk acoustic resonators and apparatus embodying the method

An apparatus such as a thin film resonator has a bottom electrode, a top electrode, and a composite layer between the two electrodes. The composite layer includes a piezoelectric (PZ) layer having a first coupling coefficient and a coupling coefficient control (CCC) layer having a second coupling coefficient. By varying the relative thicknesses of the PZ layer and the CCC layer during the manufacturing process, the coupling coefficient of the resonator can be established (to any value between the first coupling coefficient and the second coupling coefficient) with minimal impact on resonant frequency. Further, it is relatively less difficult to fabricate the PZ layer and the CCC layer having the desired coupling coefficient (as a combination of the first coupling coefficient and the second coupling coefficient) compared to the difficulties of fabrication of a uniform PZ layer having the desired coupling coefficient.

Optimal narrowband dispersionless fiber Bragg grating filters with short grating length and smooth dispersion profile

An effective optimization approach to the inverse design problems of complex fiber Bragg grating filters is developed in the present paper. Based on a multi-objective evolutionary programming (MOEP) algorithm, the proposed method can efficiently search for optimal solutions and simultaneously take into account various requirements of the designed filter. To improve the efficiency of the MOEP based algorithm, an adaptive mutation process is proposed and verified. One of the advantages of the proposed optimization method is the capability to impose additional constrains on the desired coupling coefficient, which ensures the convenience and possibility for actually fabricating the designed devices with the commercially available photosensitive fibers. To verify the effectiveness of the proposed method, an optimal narrowband dispersionless fiber Bragg grating filter for DWDM optical fiber communication systems is designed. We successfully demonstrate that complicated dispersionless FBG filters with short grating lengths and smooth dispersion profiles can be obtained by using the proposed algorithm.