Analysis of a MEMS transmission line

A microelectromechanical system (MEMS) sound waveguide is considered as a transmission line for RF signals. We analyze a device geometry of a straight one-dimensional microsize silicon rod, where a longitudinal acoustic wave is generated and detected using capacitive transducers. Linear, isotropic, and nondispersive acoustic-wave propagation is assumed. Based on the calculation of the electromechanical impedance, an electrical equivalent model is derived for the acoustic transmission line. A numerical example and a comparison to measured properties of a MEMS-transmission-line resonator shows that the characteristic impedance level of the waveguide is typically high, which causes challenges for matched termination. Solutions to overcome the matching problems are discussed.     

Electromagnetic coupling to transmission lines under complex illumination

Electromagnetic coupling to transmission lines under complex illumination is studied. The proposed method relies on the plane wave spectrum representation of the excitation fields and on the complex equivalent length formalism. Results concerning the mathematical expectation of the induced voltage and of the maximal available power at the transmission line terminations are derived.     

Transmission line models for lossy waveguide interconnections in VLSI

At high frequencies the waveguide nature of interconnections in VLSI circuits becomes important. Moreover, losses in interconnection are a major feature, not a perturbation. Here it is shown that even for such lossy waveguide structures an exactly equivalentRLGCtransmission line can be found. Equations are given determining these transmission line parameters in terms of the waveguide propagation constant and complex average power, and also in terms of integrals over the electric and magnetic field varibles. The resultingL,C, andGparameters differ from the usual static values when losses are important, and R is not restricted to the usual formula based upon a perturbation treatment of the skin effect. Consequently, semiconductor substrates can be treated. "Current" and "voltage" are found to have an abstract meaning in the equivalent transmission line. For a waveguide in a medium where conductivity and permittivity vary with position (such as a many-layered medium) an explicit formula relating "current" and "voltage" to weighted averages of transverse waveguide fields is given. A brief discussion of the reformulation of Thevenin equivalent circuit parameters in terms of reflection coefficients avoids terms such as "open circuit voltage" that are difficult to interpret for the equivalent transmission line. The framework presented allows construction of equivalent circuits for lossy waveguide interconnections, drivers, and terminations that provide correct spatial dependence in the direction of propagation and correct power relations despite the abstract nature of "current" and "voltage" in these lines.     

叉指换能器新的等效电路模型及其PSPICE仿真

声表面波器件PSPICE仿真是包含声表面波器件电子系统设计的难点,文章提出了适于PSPICE仿真的叉指换能器新等效电路模型,它应用LC网络等效Mason等效电路模型的复阻抗,由Y导纳矩阵推导计算声表面波器件的二阶效应频率特性,根据电路理论综合出与Y矩阵得到的声表面波器件二阶特性相同的等效电路,并与主信号叉指换能器等效电路模型叠加,PSPICE仿真结果与实验结果在中心频率处插入损耗和带宽相符.     

Analysis of coaxial waveguide partially filled with chiral media

In this paper, the canonical problem of coaxial waveguide partially filled with chiral media is analyzed by a new equivalent transmission line network method. Both radial transmission lines in the cross section and multi-mode transmission lines in the longitudinal direction are introduced. The symmetrical properties of the structure are also discussed. Therefore, this method brings a clear physical picture into the wave propagation phenomena. Based on the analysis, the notable features and the role of the chirality parameter of the medium on the reflected and transmitted guided waves are discussed.     

Time-Domain Green's Function-Based Sensitivity Analysis of Multiconductor Transmission Lines With Nonlinear Terminations

Time-domain sensitivity analysis of multiconductor transmission lines is derived from the dyadic Green's function of the 1-D wave propagation problem. The rational nature of the Green's function permits the generation of a time-domain macromodel for the computation of transient voltage sensitivities with respect to both electrical and physical parameters, completely avoiding similarity transformation. Through simulations of multiconductor transmission lines with linear and nonlinear terminations, comparisons are made with the perturbative approach and standard frequency-domain techniques for multiconductor transmission lines.      

Finite ground coplanar waveguide (FGC) low loss, low coupling 90-degree crossover junctions

Microwave and millimeter-wave integrated circuits and RF distribution networks often require two transmission lines to cross over each other. In this paper, experimental measurements and three-dimensional (3-D) finite difference time domain analysis are used to thoroughly characterize coplanar waveguide (CPW) and finite ground coplanar waveguide (FGC) 90-degree crossover junctions. It is shown that FGC crossover junctions have approximately 15 dB lower coupling than CPW crossover junctions. Furthermore, it is shown that the FGC junctions do not excite the parasitic slotline mode, whereas, the CPW junctions do excite the slotline mode. The results presented indicate that the FGC crossover junction is easier to implement and has better characteristics than the CPW crossover junction.     

A new radial transmission line network approach for symmetrical modes in circular chirowaveguides

In this paper, the dispersion characteristics of symmetrical modes in circular chirowaveguides are analyzed by a new equivalent transmission line network method. Radial transmission lines in the transverse cross section are introduced. In the transmission line network, the right-circularly polarized (RCP) wave and the left-circularly polarized (LCP) wave can propagate independently in the uniform regions and couple only at the interface. Therefore, this method brings a clear physical picture into the wave propagation phenomena. Based on the analysis, two interesting effects due to mode coupling and leakage are carefully studied.     

Optoelectronic measurements of picosecond electrical pulsepropagation in coplanar waveguide transmission lines

Observations are presented concerning the effects of coplanar waveguide transmission lines on the propagation of picosecond electrical pulses using an optoelectronic time-domain measurement technique. Effects of various test structure design factors such as substrate thickness, thickness of transmission line metallization, discontinuity spacing, ground plane width, pulser/sampler line length, and pulser/sampler geometry on picosecond electrical pulse propagation in microwave/millimeter wave coplanar waveguide transmission lines are discussed, and schemes for minimizing the adverse effects of each of the above factors are provided     

A new approach for closed-form transient analysis of multiconductor transmission lines

A novel closed-form model for multiconductor transmission lines is presented. The proposed model is derived from the analytical characterization of half-T ladder networks, which using closed-form polynomials (named DFF and DFFz), allow one to exactly extract poles and residues of the two-port representation of multiconductor transmission lines, thus, generating a time domain macromodel that can be incorporated in a circuit simulator. Since the model is derived from a stable and passive equivalent network, its stability and passivity are strictly preserved. Simulation results for one, two, and three-conductor transmission lines with linear and nonlinear terminations are presented, confirming the validity of the proposed model.     

Electrodynamical Model of Composite Cylindrical Structure with Laminated Dielectric

The article is devoted to the problem of the natural electromagnetic modes, the regions of their existence and the relationship with all possible types of resonances in the waveguide junction of a cylindrical and radial waveguides with a layered (laminated) filling of the radial waveguide with dielectric material. An electrodynamic model is created on the basis of a rigorous method of modal matching technique, with the separation of the common waveguide coupling region and the representation of the field in it in the form of a superposition of the fields of the partial waveguide eigenmodes. The structure under investigation can be used to measure the electrical parameters of dielectric samples of a cylindrical cross-section. It is shown that the measurements will have a local character, since the spectral characteristics of the junctions are determined mainly by the size of the central coupling region of the waveguides and by the electrical parameters of the dielectric that is in the junction. The problem of edge effects for samples of finite length (partial filling of a radial waveguide with dielectric) is investigated. Taking into account the edge effect enables reducing the error in measuring the permittivity for samples of arbitrary sizes in the investigated structure.     

High-performance traveling-wave electroabsorption modulators utilizing mushroom-type waveguide and periodic transmission line loading

For the first time, periodic loaded electrodes and mushroom-type waveguide are combined to improve the performance of traveling-wave electroabsorption modulators (TWEAMs) based on the asymmetric intra-step-barrier coupled double strained quantum well (AICD-SQW). The electrical modulation response of periodic mushroom-type TWEAM is obtained by using equivalent circuit model, and is compared with simulation result of conventional mushroom-type TWEAM counterpart. The equivalent circuit model simulation results indicate that for the exemplary modulation length of 300 mm, the mushroom-type TWEAM with periodic transmission line loading can achieve much wider bandwidth about 99.7 GHz and 43.1 GHz than the conventional counterpart with about 43 GHz and 33 GHz for 35 W and 45 W terminations, respectively.     

Hybrid Mode Analysis of Microstrip Lines on Anisotropic Substrates

A rigorous hybrid mode analysis is applied to microstrip lines on anisotropic substrates to determine its high-frequency performance. The analysis is based on a general formulation of the problem of planar transmission lines on multilayered substrates with uniaxial anisotropy, of which the microstrip line is a special case. Exact solution is obtained using a functional equation technique which was previously developed and applied to microstrip and bilateral finlines. The results were used to check the validity of the concept of equivalent isotropic substrate, suggested by some authors to simplify the calculation of the parameters of these lines. Certain approximations are introduced to allow the efficient calculation of the characteristics of microstrips on anisotropic substrates at relatively high frequencies or for wide strips. Numerical results are given for some values of the parameters of microstrip lines on sapphire and include the regions of excitation of higher modes.     

Multimode network analysis of planar transmission lines

An alternative approach for the full wave analysis of single or coupled planar transmission lines is presented. Following the proposed approach, a multiple (or single) transmission line structure is viewed as series of stacked (or single) transverse discontinuities in a parallel plate waveguide. As a consequence, both top and side coupled structures can be studied. Each individual discontinuity is described in terms of a multimode equivalent network representation. The complete cross section of the planar transmission line structure is then described in terms of a transverse equivalent network and a simple transverse resonance technique is then used to obtain the dispersion behavior, the modal field of the structure, and the characteristic impedances. The multimode equivalent network representations of the individual discontinuities used in this paper have been derived elsewhere and are given in terms of impedance or admittance matrices that are essentially independent from frequency. As a result, they need to be computed only once for each given geometry thus leading to codes that are computationally very efficient     

Finite Element Analysis of the TE Modes in Truncated-Circular Waveguide

Truncated-circular waveguide are used in some microwave and millimeter-wave components. The field patterns in truncated-circular waveguide are desired but usually difficult to be computed by conventional methods. In this paper, they are efficiently determined by using finite element method. The electrical field lines of the dominant TE mode and the first sixteen higher-order TE modes are presented. The calculated results in this paper have important values for us to understand the transmission characteristics of truncated-circular waveguide, and will be of practical significance in designing waveguide components in microwave and millimeter wave engineering.     

A vertically periodic defected ground structure and its application in reducing the size of microwave circuits

The microstrip and coplanar waveguide transmission lines combined by a vertically periodic defected ground structure (VPDGS) are proposed. The slow-wave effect, equivalent circuit, and the performances are shown. As an application example, VPDGS is adopted in the matching networks of an amplifier for size-reduction. Two series microstrip lines in input and output matching networks of the amplifier are reduced to 38.5% and 44.4% of the original lengths, respectively, due to the increased slow-wave effects, while the amplifier performances are preserved.     

ANALYSIS AND DESIGN OF MULTIPORT WAVEGUIDE JUNCTIONS WITH ARTIFICIAL INCLUSIONS FORMED OF CONDUCTING STRIPS

A rigorous electromagnetic theory is developed to analyze multiport waveguide junctions with artificial inclusions formed of the conducting strips and dielectric layers. The method is based on the Fourier transform technique combined with the mode matching method technique that takes into account the edge conditions in vicinity of the strip edges. The scattering characteristics of a 3-port junction are discussed with the numerical examples for the SWR maps, the power reflection and transmission coefficients, and the 2D plots of near fields distributions inside the junction area. A strategy of optimize matching properties of the 3-port waveguide junctions is also presented.