混合磁芯脉冲电压耦合器的宽频带电路仿真模型

采用阻抗不同的AB两种磁芯,提出了两种混合AB磁芯的脉冲电压耦合器模型,即AA+BB和A+B两种混合磁芯设计方案,然后建立了电路仿真模型进行分析;最后,制作试验电路对该耦合器进行高压电容器放电试验。高压试验结果表明,混合磁芯耦合器的仿真电压和电流波形与试验波形基本吻合,从而验证了电路仿真模型的正确性。     

Interdigital directional couplers with an odd or even number of lines and unequal characteristic impedances

A design procedure for interdigital directional couplers with an odd or even number of lines and unequal characteristic impedances of the parts is presented. Present design procedures and synthesis methods are shown to be special simplified cases of a general theory.     

Small-hole couplers

A proof is provided of the fact that the formulas for the coupling due to a small hole, obtained by Bethe, correctly apply even to structures which do not exhibit the symmetry, in the plane of the hole, postulated by Bathe.     

Wavelength-flattened fused couplers

A technique is reported for the fabrication of fused couplers, which yields devices having splitting ratios substantially independent of wavelength. A low-loss, stable, single-mode 2×2 port coupler has been fabricated using this technique. The coupler has 50/50% coupling at both 1.3 and 1.52 ?m and 50% ± 9% coupling over the wavelength range 1.23 to 1.57 ?m.     

Asymmetric multimode couplers

An asymmetric multimode coupler consists of two dissimilar multimode fibers. A simple theoretical analysis of asymmetric multimode couplers that will enable couplers to be designed with specific performance parameters is presented. The theoretical predictions are compared with the measured behavior of specially fabricated couplers. A novel technique to determine the performance of a linear bus of identical asymmetric couplers from measurements on a single coupler is introduced     

Tapered mismatched couplers

The criteria for adiabatic power flow along tapered mismatched directional couplers are discussed. The authors present the coupled local normal mode equations for tapered mismatched directional couplers. From these, the authors derive an optimally short profile for obtaining quasi-adiabatic power propagation. Apart from the trivial case where the mismatch is a constant, this is the only known mismatch profile for which analytical solutions of the coupled local normal mode equations exist. Conditions for which an adiabatic coupler can be used to obtain approximately 100% power transfer from one core to the other are also given     

Efficiency of quasi-optical couplers

Millimeter-wave devices are often coupled to radiation by means of a feed antenna placed at the focus of a primary lens or mirror, a technique known as “quasioptical coupling”. A general expression for the efficiency of such a coupler is derived. The efficiency of such a coupler depends on the relationship of the feed antenna pattern to the numerical aperture of the primary lens. An approximate general rule for coupler design is obtained. This rule is as follows. Let θ_o be the angle between the direction in which the feed pattern is maximum and the direction in which the pattern intensity has one-half its maximum value. Then the optimum numerical aperture of the primary lens is approximately sin (1.67 θ_o). The effects of focussing errors and lens aberrations can also be calculated by this technique.     

Directional couplers made of nonidentical asymmetric slabs. Part I: Synchronous couplers

We discuss TE and TM mode directional couplers made of nonidentical asymmetric slab waveguides. Approximate expressions are provided for the coupling coefficients of synchronous (no grating) couplers and their accuracy is checked by comparison with exact solutions that are based on solving the guided mode problem of the total structure consisting of the two slabs considered to be a single waveguide.     

Wavelength-insensitive fused polished couplers

Wavelength-insensitive fused polished couplers are fabricated from different fibres and from identical fibres where in the latter case one of the fibres is polished to such an extent that a small portion of its core is removed.<>     

Modelling fused single-mode-fibre couplers

The fused single-mode tapered coupler is successfully modelled by assuming that the neck section of the coupler can be represented by a rectangular dielectric waveguide. Guidance is provided at the glass-to-air (or external medium) boundary and the cores are neglected. The mechanism of field detachment from the cores is outlined and the coupler characteristics are derived from the interference between the two lowest-order modes of the large waveguide.     

High-directivity microstrip directional couplers

The letter describes a simple method for improving the directivity of side-coupled microstrip couplers an unmetallised piece of the substrate material is cemented on top of the microstrip structure. The measured directivity ranges from 30 to 40 dB. The couplers are fully compatible with normal microstrip techniques.     

Stable low-loss single-mode couplers

Single-mode optical-fibre couplers have been fabricated from standard production fibre using a fused biconical taper technique. The packaged devices have very low insertion loss (?0.1 dB), good thermal and mechanical stability, and exhibit negligible polarisation selectivity.     

Wavelength dependence of fused couplers

The transmission characteristics of fused couplers are evaluated as a function of the cross-sectional radius and the degree of fusion. The wavelength dependence of the coupling ratio is then examined with a view to minimising the wavelength dependence in wavelength-multiplexed optical networks. The effect of changing the external refractive index is also considered.     

Fused couplers of arbitrary cross-section

Simple expressions are presented to describe fused couplers of arbitrary cross-section and arbitrary refractive-index profile height. The length for polarisation splitting can depend dramatically on cross-sectional shape. Four cross-sections are compared to illustrate the concepts.     

Multi-combline warped-mode directional couplers

A first report of multi-combline warped-mode directional couplers using three lines is presented. The technique outlined can be extended to many different designs and additional lines. The specific example given has been designed as a 3-way equal power splitter with a phase difference of 180° and 0° between the two outer lines and the central line. The coupler is fed from the central line at the input. The device exhibits significant coupling over the range 0.7 to 9 GHz, but with ripples at the lower frequencies and loss at the higher frequencies the most useful range is about 3 to 8 GHz.     

Directional couplers made of nonidentical asymmetric slabs. Part II: Grating-assisted couplers

In this second part of the paper we discuss TE and TM mode directional couplers made of nonsynchronous, nonidentical asymmetric slab waveguides. Coupling is accomplished with the help of a diffraction grating that is placed on either of the two guides on the side facing the opposite slab. The grating couples the compound modes of the complete slab structure to each other. However, since the two slabs are nonsynchronous, the compound modes resemble closely the modes of each slab in isolation. We also provide approximate expressions that result from approximating the compound modes with the modes of the individual slabs. The accuracy of these approximations is estimated by comparison with the exact results.     

Finite-ground coplanar-waveguide branch-line couplers

Two branch-line (BL) couplers based on finite-ground coplanar-waveguide (FGCPW) structures are proposed. The first one uses the bended structure to reduce the size of the normal quarter-wavelength two-arm BL coupler. The second one improves the bandwidth by adding external compensated networks, which are also folded for size reduction. In this study, the performances of these BL couplers are examined, theoretically and experimentally     

180-degree ring couplers

A new type of ring coupler is propsed in which the coupling coefficient is controlled by the length of the arms. It is thought these rings may be profitably employed for breadbroads (thanks to ease of construction) and for hybrid integrated circuits, since very tight values of coupling are most easily accomplished.