T here are many ways of modeling field effect transistor (FET) devices. Physics-based models do not require any kind of measurements. They are completely based on the physics of the FET and simulate its behavior solving semiconductor equations for different geometries and doping profiles. Although these models are very flexible, they are (to date) not useful to circuit design engineers because of their huge amount of computing time. The most common way in modeling FETs is the use of an equivalent circuit. The elements of the circuit are extracted using different kinds of measurements and afterwards described using either mathematical equations or look up tables. Both equations and tables must allow interpolation between nonmeasured DC values.This article describes an efficient method for FET modeling that requires a minimum number of measurements, namely only a set of small signal scattering parameters at different bias points. The proposed method is based on spline functions, takes into account thermal and noise effects, allows a scaling of different FET device geometries, and is available in commercial CAD software like Agilents Series IV or ADS. Equivalent CircuitsThe equivalent circuit of a FET can be divided into two parts: constant and bias independent extrinsic elements and a bias dependent intrinsic part. Each element has a physical meaning. The extrinsic elements, for example, describe pad capacitances or resistivity of the transistor lines whereby the intrinsic charge zone of the FET is represented by the gate-source and gate-drain capacitances ( Figure 1).We propose an equivalent circuit [1] based on the well known 15 element circuitry [2], [3]. Some changes (Figure 1), however, are required for the nonlinear modeling:q All intrinsic elements are extracted bias dependent (both voltages) q The current source I DS is replaced by measured IV-curves I DS (V GS , V DS ) q Two Schottky diodes, which can be determined from the measured scattering parameters, describe its compression behavior September 2000 49

This paper describes the design of a novel test-set for single-ridged waveguides in the 28.5 GHz band. The test-set composes of three main parts: a waveguide transformer with a 900 bend,a part of an antenna array (slots) represented by a ridged waveguide transmission line and a load. The transformer provides a single-ridged-waveguide-to-standard-WR-28 transition and vice versa. This transition forms the interface to the measurement equipment and parts of its design will also be applied to the original design of the antenna. The load can be tested by connecting it to the singleridged output port of the adapter or to the waveguide transmission line. This saves precious development time and costs, and enables also an accurate verification of the adapter design. The waveguide transmission line can be used to test different slot configurations. Some simulations have been performed to investigate the tolerance values required for manufacturing the test-set.

Abstract-In this paper the influence of the backside metallization on a coplanar X-band low noise amplifier MMIC is described. First, we demonstrate the selection of transistor devices including the modelling especially with respect to the extraction of RF noise parameters. After that the simulation results and the layout of the LNA are presented, neglecting backside effects on coplanar circuits. Completing measurements on the fabricated LNA show the influence of the backside metallization in comparison with simulation results.

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As MMICs become more widespread in commercial appllcations the costs of production gain increased attention. For the MMIC-Designer it is important to reduce the chip size, while keeping the electrical characteristics. To demonstrate which size reduction is possible using lumped elements, this paper documents the comparison of a distributed and a lumped element MMIC K-band amplifier in coplanar line technique. The distributed element amplifier is a two-stage design and needs a size of 3 mm2. In the frequency range from 18 to 20 GHz the gain is more than 12 dB. The lumped element amplifier is a three-stage design, which has a size of 1 mm2. For the same frequency range the gain is more than 23 dB.