H.L. Hartnagel

The Design and Performance of Three-Line Microstrip Couplers

An analysis is presented of microstrip-coupler circuits consisting of three parallel lines. The analysis is based on the existence of three mode impedances. Design equations describing the performance of this type of coupler are derived and allow the prediction of its matching and transmission properties. Numerical results using finite difference methods are presented for a three-line microstrip coupler made on an alumina substrate (k = 9.8). Experimental results for a 10-dB tbree-line coupler with a center frequency of 4 GHz show that its performance can be reasonably well predicted by the developed theory.

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. >

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.

A piezoresistive GaAs pressure sensor with GaAs/AlGaAs membrane technology

This paper reports on the technology and performance of piezoresistive pressure sensors that utilize GaAs/AlGaAs membranes for pressure transduction into stress to induce resistance changes of p doped GaAs resistors. We have tested the sensor to differential pressure up to 8*104 Pa and in a temperature range of room temperature up to 433 K.

Experimental Analysis of Passive Intermodulation at Waveguide Flange Bolted Connections

In this paper, the generation of passive intermodulation at rectangular waveguide flange bolted connections is investigated. An exhaustive series of tests has been performed in order to provide understanding on the physics lying behind such a phenomenon. In particular, the intermodulation response of the system has been studied as a function of the applied torque to the flange screws. It has been found that, in some situations, the intermodulation response differs from its expected behavior. An interpretation of such discrepancies is given, and practical guidelines for the design of waveguide flanges free of passive intermodulation are provided as well

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>>

A new GaAs power MESFET structure for improved power capabilities

A GaAs microwave power MESFET structure is described that achieves a significant improvement of the gate mode attenuation by incorporating a suitably terminated transmission line parallel to the gate. The reduced attenuation allows a much wider single gate (a factor of 4 is possible) and a corresponding improvement of the total output power. It is shown that this approach leads to higher gain and cutoff frequency. An additional advantage of this MESFET structure is its higher input resistance relative to a device with equal total gate width but more gates in parallel. This results in simpler matching circuits of greater bandwidth. The single-gate structure can be connected in parallel to further increase the total output power. The results of an electrical characterization of the devices are presented, and its advantages and potential application are discussed. >

A physics-based temperature-dependent SPICE model for the simulation of high temperature microwave performance of HBT's and experimental results

A new temperature-dependent physical-based SPICE model has been developed. The simulated and experimental results for the microwave performance of HBTs up to 240/spl deg/C ambient temperature are given. Fabrication of high temperature stable HBTs is demonstrated. The origin of the deterioration of RF performance at increased ambient temperatures is investigated.<<ETX>>

Ultra-small quantum devices for memory and logic

A two-dimensional matrix of either a memory or of a logic processor can be fabricated by using a system of two double metal bridge conductors at right angles to each other over a semiconductor structure. The potential wells are the troughs of the conduction bands created by the conduction band offset of heterostructures. Thermionic transfer of the signal charge (around 100 electrons) occurs by 2 transverse pairs of 2 neighboring lines reducing the potential barrier between neighboring wells. The simultaneous signal applied to a pair of y-lines and x-lines defines a single well that can then diagonally transfer its charge to the next well. The matrix of heterostructure potential wells operates like a two-dimensional CCD. There are also signal transfer arrangements with suitable electrode configurations to operate this as a logic network.

AlGaAs/GaAs anti GaInP/GaAs HBT for high temperature microwave operation

In this paper the basics of high temperature HBTs are described. Starting from the wafer structure, and ending with obligatory technological requirements. The paper is completed by a comparison between two very promising HBT material systems in terms of high frequency and high temperature performance.