Equivalent circuit formulation for an array of phased waveguide apertures

An expression for the radiation admittance of an infinite planar array of rectangular waveguide apertures is formulated and a technique for finding the complete equivalent circuit of the waveguide to space junction is given. The formulation includes multiple layers of dielectric above the array ground plane and waveguide elements which are center loaded with dielectric. Experimental verification of the radiation admittance formulation and the equivalent circuit concepts is given.     

Equivalent circuit model for arrays of square loops

Square-loop arrays are of interest as frequency selective surfaces. Experimental results for these arrays are presented, and a simple equivalent circuit model is described which predicts the plane-wave transmission characteristics for normal incidence. These elements are a new member of the group of arrays for which simple equivalent circuits are available.     

Equivalent circuit model of quantum-well lasers

A study of equivalent circuit model of quantum well lasers derived from quantum well rate equation has been carried out. Pulse response simulation results obtained from a SPICE simulator indicates that various modulation properties, e.g., turn-on delay, relaxation oscillation frequency, and on/off aspect ratio, have a substantially different behavior than those of DH lasers. This model offers a fundamental building block for the simulation of the over all signal transmission when using quantum-well lasers as a light source     

Equivalent circuit model of on-wafer CMOS interconnects for RFICs

This paper investigates the properties of the on-wafer interconnects built in a 0.18-/spl mu/m CMOS technology for RF applications. A scalable equivalent circuit model is developed. The model parameters are extracted directly from the on-wafer measurements and formulated into empirical expressions. The expressions are in functions of the length and the width of the interconnects. The proposed model can be easily implemented into commercial RF circuit simulators. It provides a novel solution to include the frequency-variant characteristics into a circuit simulation. The silicon-verified accuracy is proved to be up to 25 GHz with an average error less than 2%. Additionally, equivalent circuit model for longer wires can be obtained by cascading smaller subsections together. The scalability of the propose model is demonstrated.     

基于广义传输线方程的矩形波导等效电路

介绍了广义传输线方程在波导分析中的应用,讨论了建立在该方程基础上的具有不连续性的矩形波导的等效电路,提出了用两个频点来提取整个频带内电路参数的方法,以加载金属膜片的矩形波导为例进行了数值计算,并应用等效电路来计算S参数,计算结果和用Ansoft公司的HFSS软件所得结果相符合.     

CPW to waveguide transition with tapered slotline probe

A new CPW to waveguide transition is developed based on the concept of tapered slot antenna and E-plane probe coupling. The transition consists of a tapered slotline probe and a slotline to CPW matching section. The current design has the advantages of broad bandwidth, compact size, low fabrication cost, and high reliability. The characteristics of a prototype transition are investigated by numerical simulation on Duroid substrate and WR-90 waveguide. The back-to-back combination is measured to verify the agreement with the simulated results and realization of this design     

Multimode deposited silica waveguide and its application to an optical branching circuit

A fabrication procedure has been developed for multimode deposited silica waveguide (DS guide), consisting of uniform and thick glass layer formation for core and cladding, and amorphous Si mask film for reactive sputter etching. The embedded multimode DS guide with a square core cross section has a transmission loss of 1.3 dB/cm at 633 nm wavelength. Waveguide parameters, such as core dimension, refractive index, and index difference, are similar to those of a multi-mode silica fiber. A multimode optical branching circuit with eight output ports was demonstrated by the above fabrication procedure. Excess insertion loss was 2 dB.     

Full-wave CAD of a rectangular waveguide filter with integratedcoaxial excitation

Coaxial waveguides are very commonly used in many microwave subsystems for the connection of various components. Significant size reduction could, therefore, be achieved by integrating the design of the coaxial transition in the computer-aided design (CAD) of microwave filters. In this context, we first discuss in this paper a coaxial transition, which can be efficiently designed interactively using an accurate and efficient CAD procedure. The key elements of the CAD tool developed are then described and a specific example of a microwave filter is discussed. In addition to theory, measured results are also presented, thereby fully validating both the CAD tool and the structures proposed     

Mode excitation in a multimode optical-fibre waveguide

For normal incidence of a Gaussian beam on a multimode optical fibre, theory predicts that only HE1m, modes are excited, and this is confirmed experimentally for a liquid-core fibre of normalised frequency v = 125. Discrete-mode propagation is observed, indicating that the amount of mode conversion due to fibre imperfections is thus very small.     

Equivalent circuit for injection-locked negative-resistance oscillators

Calculations are carried out for a van der Pol type oscillator with external force. It is illustrated how the condition of synchronisation is changed when (i) the admittance of the microwave diode is assumed to consist of an additional voltage-dependent susceptance and (ii) the frequency-determining resonator has a series reactance.     

Recurrence model analysis for multiple waveguide discontinuitiesand its application to circular structures

A general formulation for the scattering from multiple waveguide discontinuities is presented. It is based on the modal analysis technique in which the corresponding fields are expanded in terms of vector eigenfunctions and the boundary conditions are imposed at each junction. Analytic expressions for the global scattering matrices are derived using a recurrence procedure that requires substantially less computation than the traditional cascading techniques. The matrix equations are truncated in a manner that satisfies the conditions for a good overall convergence, which is illustrated for step discontinuities in circular waveguides. Numerical results are presented for a thick iris in a circular waveguide and for iris-matched dielectric window designs     

Equivalent circuit for the acoustoelectric oscillator

An equivalent circuit is proposed for the acoustoelectric oscillator, and results are presented which show that the circuit can provide a good analogue of a practical device. Suppression of oscillations and changes of the resonant frequency were observed when an oscillator was connected to a reactive load. Both of these effects may be explained in terms of the equivalent circuit.     

5 THz混频二极管等效电路模型研究

采用电磁场和电路联合仿真,基于直流测试和三维电磁建模仿真技术,建立了截止频率5 THz的混频肖特基二极管的等效电路模型。重点研究了二极管的非线性结模型和外围结构三维电磁全波仿真模型,构建了考虑实际电路形式的四端口三维电磁全波仿真模型。该等效电路模型可用于太赫兹低频段混频模块设计,该模型的建立方法也为更高频段模型的建立提供了一种参考。基于该模型设计了一款220 GHz分谐波混频器,在192~230 GHz宽带范围内,双边带变频损耗小于10 dB,测试结果与仿真结果较为一致。     

High-frequency reciprocity-based circuit model for the incidence ofelectromagnetic waves on general waveguide structures

In the present contribution we construct a high-frequency circuit model for the excitation of eigenmodes in general waveguides due to externally impinging electromagnetic waves. The circuit model, consisting of distributed sources in a transmission line model, is based on Lorentz's reciprocity theorem. The classical quasi-TEM solution of this problem is found as a special case from the full-wave model. The theory is illustrated with numerical examples of electric dipoles radiating above thick coupled lossy microstrip lines     

Equivalent circuit for radial-line/coaxial-line junction

A simple equivalent circuit is presented for a commonly encountered radial-line/coaxial-line junction. The equivalent circuit is applicable to the usual situation where the dominant modes in the respective lines are the only propagating modes.     

Equivalent circuit model for a THz detector based on the double-electron layer tunneling transistor (DELTT)

An equivalent circuit model for the double-electron layer tunneling transistor (DELTT) integrated with an antenna is presented in this paper. This device is used basically for THz detection, and the antenna is used to efficiently couple THz radiation into the device for processing. Developing an equivalent circuit model is extremely helpful in matching the antenna to the device.     

Azimuthal propagation in a nonuniform concentric cylindrical waveguide with application to the Earth?ionosphere waveguide

The problem associated with propagation in the Earth?ionosphere waveguide under geometrically perturbed conditions may be handled using a method outlined earlier for the parallel-plate waveguide. In this communication, the details are outlined, based on a transformation due to Zucker and Cohn. The equations are in the form used by Wait in his treatment aimed at justifying the two-dimensional approach.     

Analysis of oscillator circuit with hard excitation

A 2-terminal hard oscillator having fifth-degree stimulance characteristics is analysed making use of the method of nonlinear condition of oscillations. Amplitudes of both stable and unstable limit cycles are determined, and the influence of parameter values on circuit behaviour is discussed.     

LSA relaxation oscillations in a waveguide iris circuit

Large-signal computer simulations of GaAs LSA relaxation oscillations in an X-band waveguide iris circuit are presented. The study is focused on a particular oscillator and a realistic model of an experimental circuit is used. However, the results are typical for other LSA relaxation oscillators. Basic features of the microwave circuit, characteristic voltage and current waveshapes, frequency tuning with bias voltage, and oscillator starting transients are discussed. The RF output power is shown to build up in less than ten cycles. Circuit optimization for high dc to RF conversion efficiency is discussed and circuit data for nearly 30 percent efficiency are given. Finally, efficiency degradation is discussed when doping gradients are present, and effciencies of 15 and 10 percent appear possible for doping gradients as high as 20 and 60 percent, respectively. Hence, the LSA relaxation mode is shown to be less sensitive to doping gradients than the sinusoidal LSA mode.