Full-Wave Analysis of Inside Cylindrical Microstrip Lines by Finite Element Method

In this paper, a full-wave analysis using finite element method is presented to investigate the dispersion characteristics of inside cylindrical microstrip lines, which are essential to the design of some conformal microstrip circuits in millimeter wave bands. Numerical results of frequency-dependent effective dielectric constants are given for different structural dimensions and dielectric constants of substrate. Some useful conclusions are derived for the design of the special conformal microstrip lines.     

Dispersion data for open inverted microstrip on RT-duroid and fused quartz substrates

Accurate dispersion data for open inverted microstrip is presented. Two most commonly used substrate materials, namely, RT-duroid (dielectric constant 2.22) and fused quartz (dielectric constant 3.78) are considered. The work is a continuation of the earlier reported data on a similar structure, called suspended microstrip, and will be an useful addition to the millimeter-wave designer's library.     

Numerical analysis of 2D tunable HIS on GaAs support

Numerical analysis of the dispersion characteristics of a 2D tunable periodic structure in microstrip technology is presented. The high relative dielectric constant gallium-arsenide (GaAs) substrate hosts the embedded active FET switches, allowing dynamic changes in the propagation conditions of the electromagnetic wave. The position, the aperture of band-gaps and hence the value of the effective dielectric constant can be controlled. These effects will be monitored through the change of the scattering parameters for different numbers of repetition of the unit cell in the transverse direction.     

Accurate Analysis of Microstrip Lines on Lossy Biaxial Anisotropic Substrates

We have studied the behavior of the microstrip lines on lossy biaxial anisotropic dielectric substrates. A spectral-domain moment method is used with the Galerkin testing procedure to determine the dispersion characteristics of single and coupled lines. Modes of both even and odd symmetries are included. It is found that the anisotropy of the substrate has a significant influence on the propagation characteristics. The theory is verified by comparison with previously published data.     

基于左手介质后向波特性的微带天线小型化研究

基于色散性稳定、频带宽、电尺寸小的左手介质结构单元，设计了一种左手介质和传统介质相结合的微带天线基板结构，利用左手介质的后向波效应对传统介质中传播后的电磁波进行相位补偿，从而实现微带天线小型化设计.理论计算和数值仿真结果表明，工作于4.7 GHz的微带天线的物理尺寸被减小了37.92%，突破了传统微带天线的半波长要求的限制，而小型化的微带天线的增益、带宽等性能方面与传统天线相当，证明了用左手介质小型化微带天线的可行性和实用性.     

Rectangular patch antennas over electromagnetic band gap structures

In this paper, I propose a new design of a defected structure (DS) for use as an electromagnetic band gap (EBG) configuration to enhance the performance of low profile microstrip antennas. The proposed defected structure embodies a honeycomb lattice of cylindrical air holes. The proposed DS is applied to three different configurations using a dielectric substrate (dielectric constant 6 and thickness 1.5 mm); namely: a dielectric substrate backed by a defected ground plane, a defected dielectric substrate backed by a normal substrate and a defected dielectric substrate backed by a defected ground plane. The simulated values of the transmission coefficient S ₂₁ for the last one show two well-defined stop bands around 8.5 and 9.5 GHz, respectively. The first band has been used to reduce mutual coupling in a microstrip array. On the other hand, the stop band defined around 9.5 GHz has been applied to enhance the characteristics of a rectangular patch antenna and improve the operational 10-dB bandwidth.     

Effect of the Dielectric Anisotropy on the Propagation Properties of Microstrip Tapers with Height Variations

This paper deals with the design and application of nonuniform microstrip transmission lines on anisotropic substrates. A rigorous analysis is based on the use of Hertz vector potentials, moment method and transmission line theory to determine the dispersion characteristics of single and coupled tapered microstrip lines for accurate performance prediction. Results are presented for the main parameters providing the necessary information to design several devices on tapered microstrip, with variation on the strip width and dielectric height, for (M)MIC and antennas applications. A good agreement was observed with the results available in the literature for tapered lines on isotropic substrates.     

Transient response of microstrip step discontinuities on anisotropic substrate

In this paper, we present the numerical simulation of transient response of short pulse propagating through a microstrip step junction on anisotropic substrate having a tilted optical axis. In the simulation, the FD-TD method is extended to treat the cases having tilted optical axis expressed by a permittivity tensor with off-diagonal elements. The results show that the dispersion of transient signal caused by microstrip step discontinuities is quite significant and the dependence of transient characteristics of microstrip lines on the tilted angle of optical axis for anisotropic substrate can not be neglected.     

Microstrip dipoles on electrically thick substrates

Certain basic radiation properties of microstrip dipoles on electrically thick substrates are investigated, and a comparison is made with the case of dipoles printed on a dielectric half-space. It is concluded that the microstrip dipole radiation properties become sensitive to substrate loss as the substrate thickness increases, with the half-space properties obtained for an adequate amount of loss. Asymptotic formulas for radiated power and efficiency are given for both the thick substrate and half-space problems, showing the behavior with increasing dielectric constant. The method of moments is used to extend the analysis to center-fed strip dipoles, and a method of improving both the efficiency and gain of a printed antenna by using a superstrate layer is discussed.This research was supported by NSF Research Grant ESC 82-15408 and U.S. Army Research Grant DAAG-29-83-K-0067.     

X波段的圆极化微带共形阵天线的仿真与设计

为了满足X频段机载雷达天线的指标要求,使得矩形平面天线与柱面共形,通过并联侧馈方式进行馈电。在微带共形阵天线的相关理论基础上,阵元采用介电常数2.2,厚度为0.5mm的介质基板。通过HFSS12对微带共形阵天线进行仿真设计并优化。实验结果表明,在X波段内实现了方位面的全向扫描,实测阻抗带宽为9.80-10.20GHz,最大增益可达10dB,全向辐射性能稳定,满足了指标要求。     

Effects of substrate anisotropy on the dispersion of transient signals in microstrip lines

The analysis of dispersion characteristics of transient signal in microstrip lines with anisotropic substrate is developed here, with particular attention directed toward the effects of arbitrary orientations of the principal optical axis in anisotropic substrates. Numerical simulations are carried out for the propagation of transient signals, square or Guassian pulses, along microstrips with anisotropic substrates. It is shown that the dispersion characteristics is substantially affected by the change of the orientation angle of the principal optical axis in the substrate.     

Integration of microbolometers with infrared microstrip antennas

We report on various integration schemes of infrared microbolometers with microstrip antennas. The first integration design consists of two gold (Au) rectangular microstrip patches coupled along the radiating edges by a narrow niobium (Nb) strip. Devices using silicon oxide are compared to devices using amorphous silicon as antenna substrate. An extension of the twin-patch detector design is the microstrip dipole antenna-coupled microbolometer. Two ways of connecting the device to the contact pads via narrow dc leads are presented and compared. The contribution of the dc leads to the detector response is eliminated by directly connecting the dipole to the contact pads. The thermal isolation of the microbolometer from the silicon wafer is improved by incorporating air into the antenna dielectric substrate. This leads to higher detector responsivity and shifts the resonance towards longer antennas. The implementation of a bridge microstrip dipole antenna structure is also discussed.     

The dispersion characteristics of shielded microstrip lines on magnetized ferrite and anisotropic dielectric substrates

The dispersion characteristics of the dominant mode in shielded microstrip lines on magnetized ferrite and anisotropic dielectric substrates have been obtained. The solution is obtained by applying the transverse equivalent transmission line in the spectral domain and Galerkin's method. Numerical results for the frequency-dependent propagation constants are presented which could be used in designing directional couplers and isolators.     

A method for calculation of the input impedance of a microstrip electric dipole

We reduce the problem of the current distribution over the surface of a microstrip dipole in the form of a thin, perfectly conducting strip on a dielectric substrate, which is metalized on one side, to a singular integral equation with the Cauchy kernel. The complex-valued current distributions on the dipole surface are presented along with the dependences of the input impedance on the dipole-arm length normalized to the wavelength for different values of the dielectric permittivity of the substrate. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 12, pp. 1061–1070, December 2008.     

Adjusted multichannel frequency diplexer

Conclusion Relatively simple and practical way to construct multichannel diplexer using dielectric resonators placed on substrate with multiple microstrip have been developed. Band-passes less than 160 MGz at level –25 dB have been obtained using multimode structure. Further work must be done to use connected resonators.     

宽带高增益双层硅基MEMS微带天线阵列

针对传统微带天线带宽窄和增益低等问题,设计了一种易与射频（RF）前端集成的硅基微带天线。该天线设计结合MEMS工艺,将高阻硅和低阻硅通过键合工艺形成双层硅基底,来改善微带天线介质基板的等效介电常数,有效增大了天线的带宽。同时通过在地面引入缺陷地结构（DGS）,有效的抑制谐波的产生。在此基础上设计了中心频率为10 Hz,22天线辐射阵列。仿真结果表明,天线相对阻抗带宽达到15.9%,增益超过10.9 dB,比传统微带天线有明显提升,同时满足引信中天线抗干扰的要求。     

以各向异性介质为衬底的共面紧凑型光子带隙结构

共面紧凑型光子带隙（UC_PBG）结构是一种以微带基片为载体的周期性平面结构.将介质衬 底取为各向异性媒质并运用直线法进行分析，详细介绍了方法的实现过程.对不同介质参数 的UC_PBG进行了计算，结果表明，在这些UC_PBG能带结构中带隙存在甚至有所展宽. 关键词： 共面紧凑型光子带隙 各向异性介质 直线法     

Millimeter wave oscillations in a log-periodic antenna integrated with field-effect transistor

We experimentally study microwave oscillations in a hybrid integrated circuit comprising a field effect transistor and a log-periodic microstrip antenna on a dielectric substrate. The oscillations were observed both at the main resonance frequency of the antenna and at harmonics in a range of 6 to 40 GHz. The opportunities for oscillator design optimization were studied in application to the millimeter-wave range.     

Surface plasmons on corrugated metal films

The dispersion relation for a surface plasmon, propagating across a corrugated metal film on a dielectric substrate, is obtained by the method of reduced Rayleigh equations. It is found that the surface plasmon dispersion curve has an infinite number of branches. Numerical solutions of the dispersion relation are obtained for a film, characterized by a free-electron metal dielectric function and a sinusoidal profile function.     

Analytical analysis of circular-shaped microshield and conductor-backed coplanar waveguide

In this paper, a new type of circular-shaped microshield and conductor-backed coplanar waveguide is proposed. Analytic closed-form expressions for characteristic impedance and effective dielectric constant for the new line are obtained using conformal mapping method under the assumption of pure-TEM propagation and zero dispersion. The new waveguide proposed by this paper can reduce radiation to much less than the conventional coplanar waveguide and microstrip, and can reduce the current concentration at both the edges of the strip conductor.