Static capacitance of some multilayered microstrip capacitors

A new unified model, the modified Wolff model (MWM) is presented to determine the lumped capacitance of rectangular, circular, hexagonal and triangular patches on the single layer substrate and under the multilayer condition. Effect of the top shield on the lumped capacitance has also been determined. The MWM is the combination of Wolff-Knoppick model, TTL technique and single layer reduction (SLR) technique, The results of MWM have been compared against the results of SDA, FEM, dual integral method and other forms of the variational methods with accuracy between 0.5-5% for most shapes under various conditions. The present model has accuracy of SDA and other rigorous formulations. No single method has been used in the literature to determine the lumped capacitance of patches of several shapes under the multilayer and shielded condition. The MWM is fast even on the desktop computer. Thus, the model is suitable for a unified CAD for the MMIC applications     

A substrate-dependent CAD model for ceramic multilayer capacitors

In this paper, a substrate-dependent lumped-element model for ceramic multilayer capacitors is presented. The height and dielectric constant of a substrate have a significant impact on the frequency response of a chip capacitor, and these effects cannot be treated independently from the capacitor model. Rather, the equivalent-circuit parameters in the model must be made to vary in accordance with changes in the substrate. The model presented in this paper is suitable for microstrip-mounted components, and has been applied up to 10 GHz for values from 0.5 pF to 0.47 μF, and for FR-4 substrates ranging in height from 5 to 62 mil. The modeling and extraction procedure is demonstrated for 0805- and 1206-style capacitors     

柔性基底印刷叉指电容的阻抗特性研究

为降低电容制作成本,采用丝网印刷的方式在柔性PET基底上印制出可用于较高频段范围的叉指电容。首先利用电磁仿真软件设计出叉指电容的结构;然后通过实验研究了工艺参数对印刷薄膜电阻值的影响和油墨种类对印刷叉指电容阻抗特性的影响,确定合适的丝网印刷工艺参数和导电性能良好的油墨;最后,采用上述油墨和工艺参数印制了不同结构参数的叉指电容,测试了其阻抗特性,分析了不同结构参数对其阻抗特性的影响。实验结果表明:印刷叉指电容的阻抗特性与理论仿真结果一致;叉指电容所有结构参数中,指的长度和指的个数对其阻抗特性影响较大,印制的叉指电容在100~600 MHz范围内具有较好的阻抗特性。     

CAD技术在有机薄膜电容器中的应用

建立了有机薄膜电容器结构设计和热计算的数学模型。编制的金属化有机薄膜电容器的ＣＡＤ软件，对ＣＢＢ６１型聚丙烯薄膜电容器的结构设计和热计算应用表明是实用的。对其他有机材料及结构的电容器的应用正探索中。     

Equivalence of ?-function and equivalent-circuit models for interdigital acoustic-surface-wave transducers

It is demonstrated that a complete admittance matrix for an interdigital acoustic-surface-wave transducer can be obtained from a simple ?-function model, and that the results are entirely equivalent to those obtained from some of the widely used equivalent-circuit models     

陶瓷基交指微带带通滤波器的设计

设计制作了一款小型化、温度稳定性高的交指微带带通滤波器。该滤波器选择高相对介电常数的Mg_xZn_yCa_zLa_uTiO_3陶瓷材料做基板(ε_r=25,tanδ=0.000 01,τ_f=0/℃,基板厚度0.381 mm),利用HFSS仿真软件,对该滤波器在3.92~4.52 GHz通带内进行了仿真。仿真结果显示,该滤波器中心频率为4.2 GHz,相对带宽14%,带内插损小,带外抑制良好。按照仿真尺寸进行实物加工并测试,实测结果与仿真吻合良好。     

Ag(Ta,Nb)O3 thin-film interdigital capacitors for microwave applications

Epitaxial silver tantalate-niobate Ag(Ta,Nb)O₃ (ATN) films have been grown on LaAlO₃(0 0 1) single crystals by pulsed laser ablation of stoichiometric AgTa_0.38Nb_0.62O₃ ceramic target. Extensive X-ray diffraction analysis reveals epitaxial relationship between the ATN film and LaAlO₃(0 0 1) substrate. Micrometer size interdigital capacitor structures have been defined photolithographically on the top surface of ATN films. ATN/LaAlO₃ thin-film capacitors exhibit superior overall performance: loss tangent as low as 0.0033 at 1 MHz, dielectric permittivity 224 at 1 kHz, weak frequency dispersion of 5.8% in 1 kHz to 1 MHz range. Dielectric permittivity and loss tangent were also measured at the microwave range. Conformal mapping techniques were employed to extract dielectric properties of ATN film on substrate at the microwave frequency range. Theoretical properties of conformal mapping techniques for interdigital capacitors and CPW microstrip lines were discussed.     

Method for manufacturing embedded variable capacitors in low-temperature cofired ceramic substrate

A method for manufacturing embedded variable capacitors (varactors) inside a low-temperature cofired ceramic substrate is presented. A varactor is fabricated by filling a via hole with ferroelectric barium strontium titanate paste. The measured capacitance of the varactor changed from 1.47 to 0.97 pF and the Q factor from 18.2 to 31.5 at 1 GHz when the bias voltage was increased from 0 to 200 V.     

Li-doped (Ba,Sr)TiO3 thick film interdigital capacitors for microwave applications

Microwave properties of Li-doped (Ba,Sr)TiO₃ thick film interdigital capacitors have been investigated. According to the reported papers, BaSrTiO₃ materials, paraelectric state at the room temperature, have high dielectric permittivity (>500 @ 1 MHz) and low loss tangent (<0.01 @ 1 MHz) in epitaxial thin film form; however, the sintering temperature of BaSrTiO₃ is over 1350 °C. In order to reduce the sintering temperature, Li (3 wt%) was added to the BaSrTiO₃ materials, and 10 μm thick Li-doped (Ba,Sr)TiO₃ films were screen printed on the alumina (Al₂O₃) substrate and sintered at 900 °C. Interdigital capacitor patterns with five fingers of 200 μm gap and 250 μm length were also designed and fabricated by employing the screen printing method with Ag electrode. The structural feature was analyzed with X-ray diffraction method. Frequency and temperature-dependent dielectric properties were characterized from 1 kHz to 1 MHz and 303-403 K, respectively. Also, current-voltage characteristics were investigated with an elevated temperature. Microwave transmission and reflectance properties of thick film interdigital capacitors will be discussed, and frequency dispersion of dielectric properties will be presented. Specially, designed Au/Li-doped (Ba,Sr)TiO₃/Ag-Pd/Al₂O₃ vertical structure was prepared to measure the tunability. In this sandwich type structure, Li-doped (Ba,Sr)TiO₃ films showed tenability of 7.15% at a bias electric field of 20 kV/cm.     

CAD models for suspended and inverted microstrip

The accuracies of CAD models for suspended and inverted microstrip are examined, and new models are proposed. The models are compared over the range of 0.1⩽w/h⩽10 and for ϵ_r values of 3.78 and 12.9. Of the three models examined, the Tomar and Bhartia (T&B) model is shown to be the most accurate. For ϵ_r=12.9 (the worst case), the T&B model shows maximum and average errors of 2.94 and 1.28% respectively over its valid range. New CAD models are presented which demonstrate significantly improved accuracy and range of convergence. For suspended and inverted microstrip, the new models demonstrate worst case errors of 0.65 and 1.02%, respectively, and average errors of 0.23 and 0.27%, respectively. Further, the new models are valid for the full 0.1⩽w/h⩽10 range, and unlike the other models, converge for the limiting cases of either complete substrate filling or a zero thickness substrate     

Experimental evaluation of existing CAD models for microstripdispersion

Microstrip dispersion measurements covering a variety of different substrate materials and line impedances performed using the gap-coupled resonator pair method are discussed. The results of this method were compared with those obtained using nine microstrip dispersion models. The results indicate two models that are consistently accurate and are therefore recommended for CAD applications     

Multilevel metal capacitance models for CAD design synthesissystems

An empirical model for multilevel interconnect capacitance is presented. This is the first model that allows designers to compute capacitances of arbitrary complex metal geometries. Such flexibility is achieved by a novel strategy of constructing complex geometries from simple primitive cells. Agreement with accurate simulations and measurements is within 8% over an extensive range of dimensions     

Bulk waves radiated from an interdigital metallic transducer deposited on an anisotropic substrate

The whole acoustic field emanating from a metallic interdigital transducer (IDT) deposited on an anisotropic half-space is computed. Extending the classical Lamb approach, it is shown that the field can be expressed by an integral whose singularities give rise to both Rayleigh surfaces waves (SAWs) and well collimated bulk waves (BAWs). For a Y-cut, Z-propagation quartz crystal a horizontal shear wave is excited; it is shown that the orientation and width of the main lobe can be chosen by changing the frequency.     

稳压直流电源用铝电解电容器主要失效模式及解决措施

小型稳压直流电源用铝电解电容器上机后有两种规格的电容器失效率高 ,且主要失效模式为开路。开路的根本原因是电容器高度超过允许安装高度。提出了从使用方法和生产工艺方面的解决措施     

Physical and CAD models for the implanted-channel VLSI MOSFET

A new approach is described for the modeling of practical MOS transistors that have nonuniform substrate doping profiles. The threshold characteristic is used to provide an accurate measure of body charge and thereby to give operating point dependences of the threshold voltage, body effect, mobility, and weak-inversion conduction. The results are incorporated into a simple and flexible CAD model suitable for existing and foreseeable devices. The model has continuity of current and all derivatives throughout all regions of operation. It provides an accurate representation of real transistors and minimizes numerical problems of convergence and stability. It has been implemented as level-4 in SPICE 2G.5 and is freely available for VLSI circuit design.     

Efficient 3-d capacitance extraction considering lossy substrate with multilayered green's function

An efficient algorithm for extraction of three-dimensional (3-D) capacitance on multilayered and lossy substrates is presented. The new algorithm presents a major improvement over the quasi-3-D approach used in a Green's function-based solver and takes into consideration the sidewalls of 3-D conductors. To improve the efficiency of the computation and the transformation of the Green's function, a nonuniform grid is adopted. The most computationally intensive part in the transformation of the Green's function is computed separately as technology-independent matrices Tk foremost. Once computed, Tk can be stored and used for any technology, thus the storage requirement and computational complexity are reduced from O (S/sup 2/) and O (S/sup 2/ log S/sup 2/), respectively, to just O [(log S/sub max/)/sup 2/]. Extensive tests have been performed to verify the new algorithm, and its accuracy has been established by comparing with other programs.     

New physical insights and models for high-voltage LDMOST IC CAD

The lateral DMOST (LDMOST), including an LDD (lightly doped drain) and the inherent BJT (bipolar junction transistor), is studied extensively using the two-dimensional device simulator PISCES. The PISCES simulations provide physical insights into the normal- and reverse-mode operations of the LDMOST, which are used for developing a comprehensive LDD LDMOST model for circuit simulation. In the modeling methodology, the LDD LDMOST is regionally partitioned into three main components (the channel, the drift region, and the BJT), and carrier-transport problems in each component are solved. The composite physical model is implemented in SPICE for HVIC (high-voltage integrated circuit) CAD and is supported by measurements. The modeling methodology is also applicable to the Resurf LDMOST     

Spectral domain analysis of coplanar superconducting line laid on multilayered GaAs substrate

Shows the influence of superconducting strips on the propagation characteristics of a MIS or a Schottky contact coplanar line laid on a GaAs substrate. The use of superconducting strips instead of metallic strips makes it possible to decrease losses. However the main purpose of the study is t point out the influence of the superconductor on the slowing factor and on the characteristic impedance.<>     

A comparative analysis of substrate current generation mechanisms in tunneling MOS capacitors

This paper presents a critical analysis of the origin of majority and minority carrier substrate currents in tunneling MOS capacitors. For this purpose, a novel, physically-based model, which is comprehensive in terms of impact ionization and hot carrier photon emission and re-absorption in the substrate, is presented. The model provides a better quantitative understanding of the relative importance of different physical mechanisms on the origin of substrate currents in tunneling MOS capacitors featuring different oxide thickness. The results indicate that for thick oxides, the majority carrier substrate current is dominated by anode, hole injection, while the minority carrier current is consistent with a photon emission-absorption mechanism, at least in the range of oxide voltage and oxide thickness covered by the considered experiments. These two currents appear to be strictly correlated because of the relatively flat ratio between impact ionization and photon emission scattering rates and because of the weak dependence of hole transmission probability on oxide thickness and gate bias. Simulations also suggest that, for thinner oxides and smaller oxide voltage drop, the photon emission mechanism might become dominant in the generation of substrate holes.     

Two-layer interdigital transducer for acoustic-surface-wave devices

Using photomasks with the same resolution as for conventional transducers, it is shown that a 2-layer interdigital transducer doubles the operating frequency of acoustic-surface-wave devices, at the sacrifice of some increase in conversion loss. The origin of the increased loss is attributed to a geometrical factor and a dielectric loss in the insulating layer.