Direct coupling between two dielectric resonators

The letter deals with a new method of calculation of direct coupling between two dielectric resonators. This method could be used for the design of microwave integrated filters. Comparison between calculated and measured values of this coupling shows good agreement.     

Mode structure of active resonators

An analysis is made of the mode structure of lasers when the interaction with the active medium is taken into account. We consider the combined effect of gain and refractive-index variations for arbitrary mirror configurations. Using a dimensionless round-trip matrix for a medium with a quadratic variation of the propagation constant with distance from the optic axis, dimensionless beam parameters are derived in terms of cavity and medium parameters. Beam waist and radius of curvature are obtained explicitly as a function of a dimensionless parameter containing the variation of propagation constant, wavelength, and cavity length. The spot size depends only on the absolute value of the gain variation, whereas the deviation of the radius of curvature of the beam from the mirror curvature changes sign when the sign of the gain variation is reversed. As long as radial gain variations are present stable oscillations can always be obtained for any set of curved and/or flat mirrors. For large gain variations the spot size and radius of curvature of the outcoming beam become independent of mirror curvatures.     

Mode analysis in microstrip resonators part II

In this contribution, the transmission line model for a printed circuit microstrip resonator is used to theoretically investigate the modes supported by simple structures. Computer analysis yields useful information on the harmonic response of resonators that is relevant to the design of printed antennas and harmonic generators.     

Features of the coupling coefficients of planar stepped-impedance resonators at higher resonance frequencies and application of such resonators for suppression of spurious passbands

Features of the electromagnetic coupling coefficients between stepped-impedance resonators made of the sections of symmetric strip and microstrip transmission lines at higher resonance frequencies are investigated. It is found that, in stripline resonators, these coefficients are equal to zero at some coordinates of the jump of the characteristic impedance. A new method of expansion of the stopband of bandpass filters, which is based on suppression of the first spurious bandpass and frequency diversity of the main band and the second spurious bandpass is proposed. A Chebyshev bandpass filter with a center frequency of 2.45 Hz and a spurious band at 6.06 f ₀ is manufactured and tested to demonstrate the proposed method.     

Characteristics of coupling between dielectric resonators andslotline

The electrical coupling between a cylindrical dielectric resonator and a slotline is characterised experimentally. The relatively strong coupling which was obtained opens up new applications for dielectric resonators in microwave circuits     

双环耦合结构及其在多路耦合器中的应用

腔体宽带超高频(UHF)多路耦合器因其结构原因导致滤波器端口至其合路点的等效电长度过长,造成通带性能下降。为解决这一问题,提出了一种应用于腔体可调带通滤波器的双环输入/输出耦合结构。对这种结构进行了理论分析以及仿真和实验验证。结果表明:利用这种结构能够在不显著降低可调滤波器通带特性的同时实现对其阻带反射特性的独立调节,可以有效减小可调滤波器端口的等效电长度。设计了采用双环耦合结构的同轴腔可调滤波器,并且利用四个双环滤波器制作了四路的UHF多路耦合器,实验结果显示了这种耦合结构的有效性。     

Dual mode coupling by square corner cut in resonators and filters

A method for realization of dual-mode coupling in rectangular waveguide cavities is described and analyzed. The method completely replaces the coupling screw, and therefore can be used to eliminate the need for tuning in dual-mode waveguide cavity filters. It also offers a wide range of coupling values and can achieve higher power-handling capability than coupling screws. Mode matching is used to calculate the mode chart of the infinitely long square corner cut rectangular waveguide (SCCRW), the field distributions of each mode, and the resonant frequencies of the cavity. An evanescent mode rectangular waveguide is used to provide dual-mode couplings between adjacent cavities. The junction discontinuity between the SCCRW and the rectangular waveguide is modeled by a double mode-matching method, yielding modal scattering parameters of the junction. A four-pole dual-mode elliptic-function rectangular waveguide cavity filter using the coupling method was constructed. The experimental filter results showed excellent agreement with theory     

Irregular-waveguide elements coupling high-Q resonators with single-mode waveguides

A new type of element coupling a high-Q resonator with single-mode rectangular waveguides is proposed. The element is an irregular tapered section. A technique of electrodynamic calculation of such a coupling element is described. The element is experimentally investigated in the case of two-mirror open resonators. The high efficiency exhibited by the coupling element over a wide frequency band is confirmed by theoretical calculations and demonstrated experimentally.     

介稳共振腔的波型限制特性

采用几何光学理论,说明了介稳腔的分类概念和介稳工作条件.着重分析了最基本的二元介稳腔(平行平面腔、虚共心腔、实共心腔、各种零g腔)的波型区分和波型限制特性.最后讨论了与介稳腔实际应用有关的几个问题.     

Theory of spontaneous emission noise in open resonators and its application to lasers and optical amplifiers

A theory of spontaneous emission noise is presented based on classical electromagnetic theory. Unlike conventional theories of laser noise, this presentation is valid for open resonators. A local Langevin force is added to the wave equation to account for spontaneous emission. A general expression is found relating the diffusion coefficient of this force to the imaginary part of the dielectric function. The fields of lasers and amplifiers are found by solving the wave equation by the Green's function method. The lasing mode is a resonant state associated with a pole in Green's function. In this way, noise in lasers and amplifiers is treated by a unified approach that is valid for either gain guiding or index guiding. The Langevin rate equations for the laser are derived. The theory is illustrated with applications to traveling wave and Fabry-Perot amplifiers and Fabry-Perot lasers. Several new results are found: optical amplifier noise increases inversely with quantum efficiency; spontaneous emission into the lasing mode is enhanced in lasers with low facet reflectivities; and the linewidth of a Fabry-Perot laser with a passive section decreases as the square of the fraction of the cavity optical length that is active.     

GSM-R系统与应用

介绍了铁路专用通信网的现状及将在铁路专用通信网中采用的铁路移动通信全球系统(GSM—R)的组成．网络结构及特点．主要功能和延伸功能,探讨了铁路对GSM—R网络建设的特殊要求,以及在GSM—R网络建设中需要做的一些工作。     

径向耦合多腔输出系统数值模拟分析

宽带速调管放大器是雷达、通讯系统核心部件,速调管输出系统的宽带特性对速调管带宽有至关重要的作用,该文论述了借助于三维电磁场计算程序《ISFEL 3D》对径向耦合多腔谐振输出系统的一对谐振腔(主腔和副腔)做了数值模拟分析,得到了不同于普遍使用的轴向耦合双间隙腔系统的场结构、模式类别和调谐带宽特性。据此结果设计了冷测实验模型,达到了离散(频率)工作点带宽7％的要求。     

Mode coupling in tapered structures

The theory of strong mode coupling involving nonorthogonal modes is extended to tapered structures. Initially, an attempt is made to show that previous formulations of the problem of nonorthogonal-mode coupling in tapered structures are incomplete. An equation is derived which is the generalization to tapered structures of the coupled-mode formalism with nonorthogonal modes     

Analytic theory of coupling from tapered fibers and half-blocksinto microsphere resonators

Coupling from tapered fibers and polished half-block couplers into the high-Q whispering gallery modes of microsphere resonators is investigated analytically. Numerous formulas are derived to predict the external coupling Q values, and intrinsic whispering gallery loss, for arbitrary structures, and for any sphere mode. Phase-mismatch due to the differences in propagation constants between input and sphere modes is taken into account. These formulas are strictly mechanical once a simple characteristic equation is solved which relates the spherical mode orders to the resonant wave vector. Results are in very good agreement with values that are calculated by different numerical methods     

EPON系统中嵌入式系统的研究与应用

阐述了千兆以太无源光网络（EPON）系统。结合EPON系统的功能要求，指出嵌入式Linux系统是EPON系统软件设计较好的平台，提出了嵌入式Linux系统在EPON系统中的应用。     

Mode competition in free-electron masers with oversized planar Bragg resonators

The nonlinear dynamics of free-electron masers with planar Bragg resonators is studied. Here, in contrast to previous studies devoted to this class of self-oscillators, the transverse field structure is not fixed and consists of a set of modes of a regular planar waveguide. A criterion for the admissible oversize (the ratio of the gap between the plates forming the resonator to the wavelength) such that the stationary oscillation regime is stable under the variation of the electron beam parameters is obtained. It is demonstrated that, in the case of a large oversize, the synchronism mismatch variation due to the instability of the electron beam parameters should result in jumping of the oscillation frequency. It is found that different oscillation frequencies correspond to excitation of mode bunches with different transverse indices of partial waves. The region of synchronism mismatch corresponding to the excitation of the surface mode whose field localizes close to the corrugated surface is found. It is shown that, unlike regions of excitation of volume modes, this region is weakly sensitive to the gap between the plates.     

远程教学系统及应用

从网络结构、性能模块等方面介绍中兴通讯公司为埃塞俄比亚提供的远程教育方案,该方案针对非洲地区国家进行了节能和环保方面的优化设计.     

基于E型双模谐振器的源负载耦合带通滤波器设计

为实现滤波器的小型化和高性能,提出了两款中心加载的E型双模谐振器,并对其进行了奇偶模分析。在此基础上通过引入源负载耦合,采用ADS与HFSS软件进行了仿真与优化。开路支节加载与短路支节加载的E型双模谐振器分别比方环谐振器减少42.8%与52.6%。实测结果表明,设计的滤波器中心频率分别为4.22 GHz和3.75 GHz,相对带宽分别为33.6%和9.1%,带内插损分别为-0.9 dB和-1.9 dB,带外零点位置与计算仿真结果吻合良好。这两款滤波器不仅尺寸小、插损低,并且具有宽阻带、传输零点可调的优点,短路支节加载的双模滤波器在选择性与带外抑制方面性能更好,可以广泛应用于各种微波电路中。     

OTDR波形分析及在光纤测量中的应用

根据瑞利散射原理分析了脉冲信号和方波信号的回波波形,并利用数值模拟得到了其理论波形.据此自主搭建了一光纤光时域反射仪(OTDR),对样品光纤进行了实际测量,得到了与理论模拟几乎一致的实测波形.通过对实测波形进行降噪处理得到了高精度的长度测量值(相对误差仅为0.0085%)和损耗测量值(相对误差为0.086%).     

视频服务器及其在收录系统中的应用

根据河南电视台新闻中心新闻网的具体情况,介绍了视频服务器的工作原理和功能。通过对收录系统业务流程及其系统结构的描述,着重分析和研究了其核心设备视频服务器在收录系统中的计划编排、控制、手动、自动收录、分段切片收录、收录实时监测等应用特点,及其在安全方面的设计。