Simple method for the variational analysis of a generalised N-dielectric-layer transmission line

A simple method which facilitates the variational analysis of a generalised N-layer (dielectric) transmission line is described. The numerical computations of the capacitance, effective permittivity and the characteristic impedance can be easily performed on a digital computer. It should be realised that the method presented in this letter does, indeed, tremendously simplify the formidable task of the determination of the potential distribution function which meets the boundary conditions of the multilayer inhomogeneous dielectric configuration.     

The effect of an offset impedance sheet on the admittance of a slot antenna

The effect of offsetting a plasma (or dielectric) from an infinite slot antenna excited with a TEM mode in a conducting plane is considered, using an impedance sheet as a model for the plasma. Results are obtained for the change in antenna admittance as a function of offset distance for several different values of plasma (dielectric) surface impedance and characteristic antenna dimensions.     

Phase Noise Reduction of Microwave HEMT Oscillators Using a Dielectric Resonator Coupled by a High Impedance Inverter

The phase noise reduction in a configuration of the HEMT oscillator with a dielectric resonator coupled by a quarter‐wavelength impedance inverter is investigated. Two HEMT oscillators for a satellite payload system are manufactured in the same configuration except for the coupling configuration of the dielectric resonator (DR) in order to empirically demonstrate the phase noise reduction. Experimental result shows that a phase noise reduction by 14 dB can be enhanced by increasing the characteristic impedance of a coupling microstrip impedance inverter.     

Numerical modeling of ultrawide-band dielectric horn antennas using FDTD

A detailed characterization of the input impedance of ultrawide-band (UWB) dielectric horn antennas is presented using the finite-difference time-domain (FDTD) technique. The FDTD model is first validated by computing the characteristic impedance of two conical plate transmission lines (including planar bow-tie antennas) and comparing the results to analytical solutions. The FDTD model is next used to calculate the surge impedance of dielectric horn antennas using the conical plates as launchers. Design curves of the surge impedance for different choices of geometries and dielectric loadings are provided. The modeled antennas are particularly attractive for applications such as UWB ground penetrating radars (GPR) applications.     

介质填充非对称倒梯形单脊波导传输特性研究

倒梯形单脊波导具有衰减常数小、特性阻抗低、功率容量大的特性,故其适用于微波传输.研究发现填充介质倒梯形脊波导有利于实现波导小型化.采用有限元法结合Matlab编程,研究了不同对称度下的填充非对称倒梯形单脊波导的截止波长、单模带宽、衰减常数、功率容量和特性阻抗.研究结果表明:对称度较小时,填充位置在短臂侧时所得的截止波长最长,单模带宽最宽,功率容量最大,阻抗特性最小.研究结果将为填充非对称倒梯形单脊波导的应用提供理论依据.     

The Solution of Inhomogeneous Waveguide Problems Using a Transmission-Line Matrix

A method of applying the transmission-line matrix method to inhomogeneous waveguide structures is described. The technique uses open-circuit stubs of variable characteristic impedance at each node in the matrix, thereby providing an analog for a dielectric. LSE and LSM modes in rectangular waveguides, and problems involving a step of dielectric are solved. Results are given in terms of the cutoff frequency and field pattern for continuous waveguides, and the waveguide input impedance for scattering problems.     

Characteristic Impedance and Phase Velocity of a Dielectric-Supported Air Strip Transmission Line with Side Walls

The characteristic impedance and phase velocity of a dielectric-supported air strip transmission line with side walls and with center conductors having zero thickness have been obtained by means of the variational method. Green's functions are used for setting up the variational expression. Using a 22-term expansion for the charge distribution on the center conductors, the Rayleigh-Ritz method is then applied in the calculation of the characteristic impedance and phase velocity of the strip transmission line. Design curves are presented and a correction factor is derived that can be applied when the thickness of the center conductors is not zero. The design curves are quite general and apply equally well to any isotropic dielectric material that is used as a support, regardless of its dielectric constant. The experimental data presented verifies the theoretical results.     

Slotline impedance

A theoretical model is presented to compute the characteristic impedance and wavelength in a slotline printed on or embedded in a dielectric substrate. In this treatment the effects of the fringing field caused by the finite width of the conducting strips are taken into account. The main task is to calculate the capacitance per unit length of the slotline. First, the Green's function for the potential of a pair of filament sources in a dielectric substrate is solved; this is used as a building block to construct the overall solution of the boundary value problem. Then, the surface charge density on the conducting strips is found by using a moment method and imposing the source condition (equal potential) on the conductors. From the surface charge density, the characteristic impedance of the slotline is computed for various input parameters. The formulation is applicable to a single-sided, sandwiched, or double-sided slotline printed on or embedded in a dielectric substate     

Metallization thickness in bilateral and unilateral Finlines

The theory and numerical results are presented to the effective dielectric constant and characteristic impedance of bilateral and unilateral finlines with metallization thickness. The full wave analysis of the transverse transmission line — TTL method is used to determine the electromagnetic fields of the structure in Fourier transform domain — FTD. Applying the suitable boundary conditions and the moment method, a homogeneous matrix system is obtained and the effective dielectric constant is extracted. The characteristic impedance is obtained using the relation between the voltage in slot and the transmitted power. Computational programs are developed to obtain numerical results to the effective dielectric constant and characteristic impedance.     

传输／反射法测量材料电磁参数的研究

分析了材料样品填充的矩形波导或同轴线等效网络的归一化通用矩阵,提出了一种求解材料电磁参数（εr,μr)的解析方法。分析表明,行性阻抗Zc与传播常数数γ均可直接由传/反射参数确定。同时应用特性阻抗与传播常数得到了磁性材料的电磁参数（εr,μr)。利用特性阻抗Zc、传播常数γ以及同时利用二者分别得到了三个确提高测量精度并确定测量误差;同时,可用于解决复介电常数测量的多值性问题与π模糊性问题。实际测试结果证明本文方法的有效的且有实用意义。     

Theoretical and Experimental Investigation of Asymmetric Coplanar Waveguides (Short Papers)

Conformal mapping techniques are used to obtain analytic closed-form expressions for the characteristic impedance and the relative effective dielectric constant of asymmetric coplanar waveguide with infinite or finite dielectric thickness. The line asymmetry leads to a decrease of its characteristic impedance and to an increase of its relative effective dielectric constant. Six asymmetric coplanar waveguides are realized and their characteristic impedances are measured using time-domain reflectometry techniques. The experimental results show very good agreement with the theoretical ones.     

Frequency-dependent characteristics of thick microstrip lines in lossy multilayered dielectric media

The Spectral Domain Approach (SDA) is used for a rigorous full-wave analysis of thick microstrip lines embedded in lossy multilayered dielectric media. The effects of the conductor thickness on the propagation constant and characteristic impedance are investigated.     

Generalized microstrip on a dielectric sheet

A procedure is described for arriving at a close approximation to the capacitance between symmetrically placed conducting strips, possibly of different widths, on opposite sides of a dielectric sheet. The procedure is based on static methods, following K.G. Black and T.J. Higgins (1955) for total capacitance of the structure with vacuum dielectric everywhere, and using H.A. Wheeler's (1964) method for determining the series component of dielectric capacitance. Dielectric polarization is included while refraction at the vacuum/dielectric boundary is ignored in the method; its effect is subsequently shown to be small. The derived equations are valid for all finite impedance, all values of relative dielectric constant, and all conductor widths. The maximum absolute error is estimated to be O(0.001Z'), where Z' is the impedance of a generalized microstrip on a dielectric sheet     

Dispersion in finlines on semiconductor and the S-parameters of a step discontinuity

The Transverse Transmission Line method is used for the characterization of bilateral and unilateral finlines on a semiconductor substrate and in conjunction with the modal method, for the calculation of the scattering parameters due to a step discontinuity on a unilateral finline with a lossless dielectric substrate. Numerical results of the effective dielectric constant, attenuation constant and characteristic impedance for the bilateral and unilateral finlines on semiconductor substrates, and results of scattering parameters of a step discontinuity for unilateral finline, are presented.     

Characteristic impedances of microstrip and finline with uniaxialor biaxial anisotropic substrates

Spectral domain analysis (SDA) is extended to compute the frequency dependent characteristic impedance Z(f) of boxed microstrip and unilateral or bilateral finlines, printed on biaxial anisotropic dielectric substrates. The most usual impedance definitions have been used     

V波段介质加载梯形慢波结构研究

研究了V波段介质加载梯形慢波结构。通过在耦合槽和间隙处进行适当介质加载,降低主模的相速,改善色散特性。使用CST对其慢波结构进行仿真,得到色散曲线和耦合阻抗,结果表明介质加载对耦合阻抗的影响很小,但却可以明显地降低相速,同时色散特性也更为平坦。     

A low-impedance coplanar waveguide using an SrTiO3 thinfilm for GaAs power MMIC's

A novel structure for coplanar-waveguide transmission lines with low impedance and low loss is demonstrated in this paper. The new structure simply has a high dielectric SrTiO₃ thin film underneath the coplanar conductors. Due to the high dielectric constant of SrTiO₃, the coplanar line exhibited characteristic impedance as low as 18 Ω with a slot width of 5 μm and the center conductor width of 50 μm, while a conventional coplanar line on GaAs showed only 30 Ω with the same configuration. The newly developed coplanar structure is easily applicable for present GaAs monolithic-microwave integrated-circuit (MMIC) technology, especially for power MMIC's and low-impedance devices     

Calculation of the input impedance of a strip loop antenna located on a dielectric cylinder

A method for calculating the input impedance of a loop antenna (LA) located on a dielectric cylinder is developed. The integral equation (IE) for the unknown function of the current density distribution on the LA surface is obtained. A numerical method for the IE solution is described. An approximate formula for calculation of the LA input impedance is proposed. Plots of the input impedance on the LA length are given.     

Electromagnetic scattering from composite objects using a mixtureof exact and impedance-boundary conditions

Different surface integral equations for characterizing the electromagnetic scattering from a surface impedance object partially coated with dielectric materials are presented. The impedance boundary condition (IBC) is applied on the impedance surface and the exact boundary condition is applied on the dielectric surface. The resulting integral equations are solved for bodies of revolution using the method of moments. The numerical results are compared with the exact solution for a sphere. Other geometries are considered, and their results are verified by comparing results of the numerical solutions which were obtained using different formulations. The internal resonance problem is examined. It is found that the combined field integral equation (CFIE) can be used at any frequency and with any surface impedance