K. Beilenhoff

Improved finite-difference formulation in frequency domain for three-dimensional scattering problems

The finite-difference method in the frequency domain is a powerful tool for analyzing arbitrarily shaped transmission-line discontinuities and junctions. An improved formulation based on Maxwells equations in integral form is presented. It corresponds to the Helmholtz equation and reduces the numerical efforts in solving the large linear equation system considerably. The method is verified by comparison to previous work on microstrip. >

Open and short circuits in coplanar MMIC's

Coplanar MMIC stub configurations are investigated by means of the finite-difference method in the frequency domain. The open end, the short end, and a capacitively loaded short end (MIM-short) are analyzed. Their parasitic effects are described in terms of the effective length extension l/sub ext/. The influence of the different line parameters is discussed and simple design rules are given. >

GaAs monolithic integrated microwave power sensor in coplanar waveguide technology

We present the fabrication technology, theoretical and experimental results of a novel MMIC compatible broadband power sensor. With a 50 /spl Omega/ coplanar waveguide design, integrated AlGaAs thermoelectric sensor and GaAs bulk micromachined membrane for increased sensitivity this sensor is capable of detecting RF power with a sensitivity of 1.1 V/W without any waveguide coupling structure.

Unified model for collector charge in heterojunction bipolar transistors

The base-collector capacitance and the collector transit-time in GaAs-based heterojunction bipolar transistors depend not only on base-collector voltage, but also on collector current. This has to be taken into account in a large-signal model. However, since collector transit-time and capacitance are both caused by the charge stored in the collector space-charge region, it is not possible to model them independently of each other. This paper investigates the interrelation between collector capacitance and transit-time due to transcapacitance effects, and presents an analytical unified description for both quantities, that is derived from measurement-extracted small-signal equivalent circuits. The model is verified by comparison of simulation and measurement data.

Treatment of field singularities in the finite-difference approximation

Due to the discretization of space, the finite-difference method cannot exactly resolve singularities of the electric and magnetic fields at metallic edges. A simple method which reduces the corresponding error without increasing the numerical efforts is presented. The novel edge formulation is tested by calculating the line parameters and the field pattern of a homogeneous MMIC (monolithic microwave integrated circuit) coplanar waveguide. This improved formulation, developed by incorporating a correction factor depending on the field singularity at the edge, reduces the errors by a factor of about one half.<<ETX>>

Scalable GaInP/GaAs HBT large-signal model

A scalable large-signal model for heterojunction bipolar transistors (HBTs) is presented in this paper. It allows exact modeling of all transistor parameters from single-finger elementary cells to multifinger power devices. The scaling rules are given in detail. The model includes a new collector description, which accounts for modulation of base-collector capacitance C/sub jc/ as well as for base and collector transit times due to temperature effects and high-current injection. The model is verified by comparison with measurements of GaInP/GaAs HBTs.

FDFD full-wave analysis and modeling of dielectric and metallic losses of CPW short circuits

A finite-difference method in the frequency domain (FDFD) is used to analyze the influence of lossy materials on the scattering behavior of CPW short ends. Not only dielectric losses but also realistic metallic losses are taken into account for the first time in an FDFD method. Both, the numerical results for the three-dimensional structure and the complex propagation constants of the homogeneous waveguide are presented. These are compared with those yielded by an analytical method and shown to be of good agreement. Finally, a simple model is presented, which describes the CPW short end with good accuracy.

Finite-difference analysis of open and short circuits in coplanar MMICs including finite metallization thickness and mode conversion

Open and short circuits as used in MMICs (monolithic microwave integrated circuits) are investigated by means of a finite difference method in the frequency domain. Both mode conversion and finite metallization thickness are accounted for. For the open stub, noticeable mode conversion is observed, whereas the short circuit behavior shows a significant dependence on metallization thickness.<<ETX>>

Fully monolithically integrated feedback voltage controlled oscillator [using PHEMTs]

A fully monolithically integrated voltage controlled oscillator (VCO) using feedback technique is presented here. The circuit provides oscillation within the frequency range of 6.3-7.0 GHz. The corresponding tunable relative bandwidth is 10%. The feedback topology proves to provide a good linearity of the oscillation frequency dependence versus tuning voltage. The maximal deviation of the frequency behavior from its linear fit is /spl Delta/f=39 MHz. It is shown in the following that the feedback technique can be used for broadband VCO design.

Analysis of T-junctions for coplanar MMICs

T-junctions are basic elements for each coplanar MMIC. This paper presents a comprehensive analysis of the scattering behavior of three different junction types. Useful information for circuit design is provided as well as simple models describing the parasitics.<<ETX>>