Characterization of a 90° microstrip bend with arbitrary mitervia the time-domain finite difference method

A 90° microstrip bend with an arbitrary miter is characterized using the finite difference time-domain (FDTD) method. In this method, to simplify computations, the microstrip structure is enclosed by four electric walls; thus radiation effects are neglected. Time histories generated by FDTD techniques are Fourier-transformed to yield broadband scattering parameters of the microstrip bend. A miter is introduced to improve the transmission characteristics of the bend, and an optimal miter length is found such that the reflection from the microstrip bend over a broad frequency range is minimized     

Characterization of radiation loss from microstrip discontinuitiesusing a multiport network modeling approach

A convenient method for evaluating radiation loss from microstrip discontinuities is presented. A planar multiport network model of the discontinuity configuration and the segmentation method are used to evaluate the voltage distribution around the edges of the discontinuity. This voltage distribution is expressed as an equivalent magnetic current line source distribution which is used to calculate the far-zone field (for radiation loss). As an example, the results show that for a 90° bend in a 50-Ω line on a 10-mil-thick substrate with ϵ_r =2.2, the radiation loss is 0.1 dB at 30 GHz. Typical power levels radiated by several other discontinuities are reported. The analysis model was verified experimentally by fabricating microstrip resonators with discontinuities incorporated therein and measuring the Q factors of these resonators     

Compact shorted variations of circular microstrip antennas

A circular microstrip antenna has been modified by shorting along the zero field to yield shorted semi-circular and 90° sectoral microstrip antennas. Experimental results on these antennas are presented. The shorted 90° sectoral antenna results in a size reduction of four times without any significant change in performance. The area is further reduced by partially shorting one of the edges of the 90° sectoral antenna     

Modeling three-dimensional discontinuities in waveguides usingnonorthogonal FDTD algorithm

A generalization of the finite-difference time-domain (FDTD) algorithm adapted to nonorthogonal computational grids is presented and applied to the investigation of three-dimensional discontinuity problems. The nonorthogonal FDTD uses a body-fitted grid for meshing up the computation domain and, consequently, is able to model the problem geometry with better accuracy than is possible with the staircasing approach conventionally employed in the FDTD algorithm. The stability conditions for the nonorthogonal FDTD algorithm are derived in two an three dimensions. Numerical results, including an H-plane waveguide junction, a circular waveguide with a circular iris, a circular waveguide with a rectangular iris, and a microstrip bend discontinuity, are presented to validate the approach     

Application of the three-dimensional finite-difference time-domainmethod to the analysis of planar microstrip circuits

A direct three-dimensional finite-difference time-domain (FDTD) method is applied to the full-wave analysis of various microstrip structures. The method is shown to be an efficient tool for modeling complicated microstrip circuit components and microstrip antennas. From the time-domain results the input impedance of a line-fed rectangular patch antenna and the frequency-dependent scattering parameters of a low-pass filter and a branch-line coupler are calculated. These circuits were fabricated and the measurements made on them are compared with the FDTD results and shown to be in good agreement     

Compact shorted variations of triangular microstrip antennas

Equilateral and triangular 30°-60°-90° microstrip antennas have been modified by shorting along the zero field to yield shorted 60 and 30°-sectoral microstrip antennas, respectively. Experimental results on these antennas are presented. The shorted 60 and 30°-sectoral antennas result in area reduction by factors of 2.5 and 5.0, respectively, compared to the equilateral triangular antenna with the same resonant frequency. The frequency is further reduced by partially shorting the curved edges of the sectoral antennas     

PCB上微带线的电磁耦合时域建模分析方法

基于时域有限差分方法和传输线方程,结合高效网格建模技术,文中提出了一种高效的时域建模算 法,它能有效解决微带线的电磁耦合建模问题,实现空间电磁场与微带线瞬态响应的同步计算。首先,结合经验公 式,计算得到微带线的单位长度分布参数,构建适用于微带线电磁耦合分析的传输线方程。然后,采用时域有限差 分(Finite-Difference Time-Domain, FDTD)方法,结合非均匀网格技术和自动网格生成技术,仿真得到微带线激励场, 并在每个时间步进上引入传输线方程获得等效分布源项。最后,对传输线方程使用FDTD 的中心差分格式进行离 散,实现微带线及其端接电路上瞬态响应的迭代求解。为了验证时域建模算法的正确性和高效性,通过自由空间和 屏蔽腔内PCB 上微带线电磁耦合的数值模拟,从计算精度和耗时两方面与传统FDTD 方法的计算结果进行了对比。     

Design of ideal structures for lossless bends in optical waveguidesby conformal mapping

We propose an ideal structure for lossless bends in optical waveguides for the first time. The ideal structure is obtained by applying a series of conformal mappings to transform a single-mode straight waveguide into the equivalent bend configuration. The expressions used to determine the waveguide path and the refractive index are derived for the lossless bends with arbitrary bend angles, even up to 90°. Also, variations in the waveguide path and the refractive index are illustrated by adopting lossless bends with six different bend angles (4, 10, 30, 45, 60, and 90°). The simulated results show that the refractive-index distribution can be controlled within the range of interest for the practical bend structure. Moreover, the characteristics of the phase front for the modal field in a lossless bend are thoroughly discussed to verify that no transmitted power would be lost by conversion to radiation modes     

Design of 10 dB 90° branch line coupler using microstrip linewith defected ground structure

The authors present a 10 dB 90° branch line coupler operating at 1.8 GHz and having a defected ground structure (DGS), a type of periodic structure realised by etching on the ground plane under the microstrip line. Owing to the additional effective inductance of the DGS, the characteristic impedance of the microstrip line is increased for the same width of conductor. A microstrip line of 150 Ω of characteristic impedance with 1 mm conductor width is realised by adding the DGS, while 1 mm corresponds to 82 Ω of conventional microstrip line on the RT/Duroid 5880 substrate with 2.2 dielectric constant and 31 mils of thickness. It is shown that a 90° branch-line 10 dB coupler can be fabricated using the 150 Ω line with DGS. Its measured performances are in good agreement with the predicted results     

Rigorous evaluation of the vertex effects on thefrequency-dependent circuit parameters of an open-ended microstrip line

This study presents the original inclusion of right singular vertex conditions in integral equations solved by the method of moments for accurate evaluation of the frequency-dependent microstrip discontinuity models required in microwave integrated circuits (MIC) and monolithic microwave integrated circuits (MMIC) design. The 90° wedges singularity function for the current density, weighted with a novel sampling function for “corner cells,” and the harmonic Green's function for shielded structures, is accurately and efficiently integrated in the conical geometry of the 90° sector. The frequency-dependent effective length and excess equivalent capacitance of a shielded open-ended microstrip line are calculated to a higher accuracy with respect to previous two-dimensional and three-dimensional “full wave analyses”     

An analysis of microstrip with rectangular and trapezoidalconductor cross sections

The finite-difference time-domain (FDTD) technique is used to analyze boxed microstrip with both rectangular and trapezoidal cross sections. It is confirmed that the exact shape of the conductor has a marked effect on the effective permittivity of the microstrip. Results using this method are compared to the findings of K.A. Michalski et al. (1989) using the analytically more complicated boundary element method; very good agreement is observed. The effect of adding a thin passivation layer is also calculated and it is found that such an addition noticeably reduces the effective permittivity of the microstrip. It is shown that the FDTD technique is capable of treating microstrip with a general cross section and producing accurate results     

Analysis of microstrip discontinuities by FDTD method combined with SOC technique

In this paper, the application of the finite-difference time-domain (FDTD) algorithm combined with the short-open calibration SOC technique to three-dimensional microstrip discontinuity is presented. This SOC technique is directly accommodated in the FDTD algorithm. It is used to remove the unwanted parasitic errors brought by the approximation of the impressed voltage sources and the feed lines. The FDTD is formulated in such a way that the port voltages and currents are explicitly represented through relevant network matrices. This new method is also used to analyze finite periodic structures. The scattering parameters of the whole periodic structure can be approximately obtained through analyzing only one cell of it. The results for microstrip discontinuities and finite periodic structures are compared with the conventional FDTD method.     

探针馈电圆柱共形微带天线阻抗特性的FDTD法分析

将圆柱坐标系下非分裂式理想匹配层吸收边界条件(UPML)引入到圆柱共形微带天线的全波分析中，并给出了其中的场量迭代方程，明显地减小了计算空间，简化了编程；提出了圆柱坐标系下考虑有限尺寸探针半径的新算法，使得计算结果更加精确；应用GPOF方法预估了时域晚时响应，使计算时间减少了70％～90％。本文给出的模型能够对任意多层圆柱共形结构的微带天线进行计算，因此对此类天线的CAD设计具有实际意义。     

Multiport power divider-combiner circuits usingcircular-sector-shaped planar components

A sector-shaped configuration for designing planar power divider-combiner circuits that are compatible with microstrip circuits is discussed. This configuration is analyzed using the two-dimensional planar circuit approach. Expressions for impedance matrix parameters of multiport sectorial planar circuits are given. Theoretical and experimental results reported for 90° and 180° power dividers are in good agreement     

FDTD方法分析光子带隙微带结构

本文采用时域有限差分法分析计算了一维光子带隙微带结构的S参数,并设计制作了光子带隙（PBG）微带线,进行了测量。将计算结果与测量结果对比可以看出两者吻合得比较好,说明采用的分析方法是有效的。     

Study of impedance and radiation properties of a concentricmicrostrip triangular-ring antenna and its modeling techniques usingFDTD method

A concentric microstrip triangular-ring antenna structure using the log-periodic principle for increasing the impedance bandwidth of the microstrip patch antenna is described. The finite-difference time-domain (FDTD) method is applied to analyze the proposed structure. A special technique to model the slanted metallic boundaries of the triangular ring has been used in the general FDTD algorithm to avoid the staircase approximation. The method improves the accuracy of the original FDTD algorithm without increasing the complexity. The radiation patterns at different frequencies over a wide bandwidth are obtained experimentally     

Analysis of Millimeter Wave Microstrip Circulator with a Magnetized Ferrite Sphere by FDTD Method with Modified Matrix Pencil Method

In this paper, the modified matrix pencil (MMP) method is used in the finite difference time domain (FDTD) method to eliminate the late time instability of time domain responses when analyzing the novel microstrip circulator with a magnetized ferrite sphere. The frequency dependent scattering parameters: reflection, isolation and insertion parameters of the microstrip circulator calculated over a wide band of frequencies with this hybrid method are compared with that obtained by direct FDTD method which agree well with the experimental results.     

双极化口径耦合微带天线FDTD分析

本文应用时域有限差分法（FDTD）分析了双极化口径耦合多层微带贴片天线。文中结果表明,FDTD在分析多层复杂结构的微带天线时是非常有效的。采用Gauss脉冲激励,通过FFT,一次计算就可得到天线谐振频率、耦合、频带宽度、增益等参数的宽频带特性。计算结果对天线的优化设计具有一定的指导作用。     

Analysis of shielded membrane microstrip line using the finite-difference time-domain method

A simple and efficient analysis method of the shielded membrane microstrip (SMM) line using the finite-difference time-domain (FDTD) method is presented. New FDTD equations are derived using the contour path FDTD concept for the Yee cell which contains three thin dielectric sheets of membrane. The characteristic impedance and the effective dielectric constant of the SMM line are calculated using our proposed method. The method is validated by comparison with the results shown by Robertson et al. [1996].     

同轴馈电耦合微带天线的MPSTD-FDTD分析

将多区域时域伪谱(MPSTD)与时域有限差分(FDTD)相结合的混合算法应用于同轴馈电耦合微带天线的分析,该混合算法充分发挥两种时域算法的优越性,对同轴馈电耦合微带天线进行了准确建模与快速分析,数值仿真验证了该算法的有效性和准确性。