Enhancement of Coplanar Capacitor Models and Verification Up to 67GHz for (M) MIC Circuit Design

Abstract

ABSEACTThe IMST has recently built up a library with recently more than 18 coplanar elements for CAD applications (2), (3). The theory of the parametric models is based on a quasi static 3D Finite Difference formulation (1). Naghed also introduced in (1) the model of a coplanar interdigital capacitor and presented the verification of this element up to 25GHz. Beyond 40GHz and for long fingers these simulation results diverge from measured data. This paper will report on the enhanced coplanar IDC model and 2 new types of coplanar capacitorsa serial and a parallel MIM capacitor, where line effects are taken into account. The equivalent circuit elements are determined in units per length. The simulated results will be compared with measured data from test circuits on a GaAs wafer up to 67GHz. Parts of these activities are supported by the European Community within the ESPRIT CLASSIC project. IITRQDUCTIONOne goal of the research activities within the IMST is the development of a comprehensive library with all coplanar structures, which are necessary for (M)MIC design. This library consists of one ports like open and short, a coplanar transmission line, discontinuities like bend, tee and cross (with different kinds of airbridges) as well as lumped elements and coupled lines. The focus of (2) lies on the evaluation of the line and discontinuity models. The coplanar spiral inductor and its application in (M)MIC is presented in (4). This paper will complete the investigations of the coplanar catalogue: an improvement of the IDC model of (1) and the development of a serial and parallel MIM capacitor. Within the ESPRIT Classic project a GaAs wafer has been fabricated at the Daimler Benz foundry in Ulm. The design and evaluation of the test circuits is the task of the authors within Classic. These test structures are simple coplanar circuits, especially developed for the verification of the models. On the wafer are structures for measuring the IDC and MIM models, too. The results have been utilised for the verification of the new models and will be presented within this paper. Up to now capacitor models in CAD programs show poor results at high frequencies. Some models have been extracted from experiments (5). Another possibility is the full wave analysis, presented in (6), which is not suitable for the circuit design with optimisation. The capacitor models presented in this paper have a parametric interface and are integrated and tested into a CAD tool. COPLANAR 1NTERDIGITAL CAPACITOR MAG(S1 1) [dB] _ 0 0MAG(S 12) [dB] 0 -20' -0,5~~~~~~~-15 -,

CAD modeling of coplanar waveguide interdigital capacitor

“…Most of these studies concentrated on the design and analysis of microstrip interdigital capacitors. Very few tried to study CPW IDCs [15][16][17]. A 3D static finite-difference method (FDM) was used in [15] to characterize the CPW IDC and other CPW discontinuities.…”

“…A -network of three capacitors was used to model the CPW IDC. A modified model that consists of Ncoupled lines in a coplanar environment was used to model the CPW IDC in [16]. Full details of this technique are not available in the literature.…”

“…A more general CPW IDC is shown in Figure 2 [16,17], in which the reference planes will still be at both ends of the IDC, while the rest of the structure (to the left and right of the IDC) can be modeled as CPW transmission-line sections along with CPW step discontinuities.…”

Growth and high frequency characterization of Mn doped sol-gel PbxSr1−xTiO3 for frequency agile applications

“…The configuration used to characterize the microwave properties of our PST films is based on the design proposed by Kulke et al,20 shown in Fig. 2.…”

“…3, is similar to that used by Kulke et al 20 but includes the impedances due to overlap of the top and bottom electrodes and also a resistance in parallel with the PST capacitance to account for the dielectric loss. R TE , R BE , L TE , and L BE are the resistances and inductances of the top and bottom electrodes in the MIM stack, while R PST and C PST are the resistance and capacitance of the PST thin film.…”