T. Sporkmann

A comprehensive evaluation of quasi-static 3D-FD calculations for more than 14 CPW structures-lines, discontinuities and lumped elements

This paper reports on the on wafer evaluation up to 67 GHz of a complete library of coplanar elements for application in MMIC design. The elements under consideration were fabricated on GaAs and simulated utilising a quasi-static 3D-FD tool and measured by a state-of-the-art measurement system. This library covers the range from transmission lines over discontinuities/junctions to lumped elements like inductors, resistors (TFR) and capacitors (MIM). Transmission line effects of TFRs with high DC values and MIMs with relative large geometries are also discussed in this paper.<<ETX>>

New types of MMIC circulators

Circulators can be used to separate transmit/receive (T/R) signals and for two-port tuners. Conventional ferrite devices are not applicable for MMICs. Two new types of electronic circulators are presented in this paper covering the frequency range from 1.8 GHz up to 80 GHz.<<ETX>>Circulators can be used to separate transmit/receive (T/R) signals and for two-port tuners. Conventional ferrite devices are not applicable for MMICs. Two new types of electronic circulators are presented in this paper covering the frequency range from 1.8 GHz up to 80 GHz.<<ETX>>

Active CPW MMIC Circulator for the 40 GHZ Band

For the first time, several active coplanar circulators have been designed and fabricated for the 40 GHz band. The technology for these circuits is the PM-HFET technology from Daimler Benz in Ulm. The introduced designs utilize the new CPW model library in the CAD package LIBRA. The return loss of the electronic circulator is better than ¿15 dB and the insertion loss is typically ¿3 dB for a bandwidth of about 6 GHz at a center frequency of 40 GHz. The isolation between the ports is better than ¿20 dB in the frequency band. New designs on InP and GaAs have been made for frequencies up to 80 GHz.

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

The 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 capacitors - a 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.

A Combined On-Wafer Measurement Stand for Linear and Nonlinear Microwave Measurements

A novel approach is presented for a measurement system which is able to investigate the most relevant specifications of microwave circuits and components. The test stand is configured for on-wafer measurements up to 60 GHz, but can also be used for connectorized device measurements. The current capabilities of the system are power and gain measurements including harmonic power and harmomc impedances. Other capabilities include active load-pulling, the spectrum and phase noise of oscillators and noise figure measurements. Furthermore, a new calibration method has been developed which allows the measurement of absolute values of all power waves at the device under test without using frequency converting standards in the calibration.

A Combined Measurement Stand for Linear, Nonlinear and Noise Measurements of Microwave Devices and Circuits

A novel approach is presented for a measurement system which is able to investigate the most relevant specifications of microwave circuits and components. The test stand is configured for on wafer measurements up to 60GHz, but can also be used for connectorized device measurements. The main measurement capabilities of the system are: Two and three port scattering parameters, noise figure and noise parameters of two port devices, power and gain measurements including harmonic power and harmonic impedances, all mixer parameters including conversion noise, active load pulling and the spectrum and phase noise of oscillators. Furthermore, a new calibration method has been developed which allows the measurement of absolute values of all power waves at the device under test without frequency converting standards. The system operates in combination with an automatic wafer probing system. The control software for the prober can be integrated in the measurement system software giving the capability of performing wafer mapping of MMICs.

Accurate new scaling routines for any table/function based FET model including temperature and noise behaviour

In this paper we present new scaling routines for any table/function based nonlinear FET model. These measurement based routines are very accurate and can also be used to calculate temperature behaviour. Also the prediction of noise behaviour is possible for scaled devices.

Vector Corrected On-Wafer Power Measurements of Frequency Converting Two-Ports

In this paper a universal nonlinear measurement system is presented. The On-Wafer approach described here is commercially available and utilizes a modified vectorial network analyzer (Wiltron 360 B) and a special software package developed at the IMST. The system determines the complex quantities of all power waves at all ports of the DUT. Since measurements are carried out at all interesting hamionics, the system is ideal for the complete electrical characterization of a frequency multiplier for instance. In contrast to other power and harmonic measurement approaches using VNAS, the technique proposed here does not need an additional microwave synthesizer for locking the receiver to the harmonics. The described system exhibits a power sweep range of more than 80 dB.

Foundry Cell Oriented Design of Active Coplanar Power Dividers and Combiners for MMIC Applications

New types of active three ports, based on conventional foundry devices, are presented. Utilising these new devices, active power combiners, dividers and switches may be realised. The modelling of these new type of devices is simply possible by networking individual HEMTs. Measurement and simulation are in excellent agreement. Three different devices will be compared and scaling results are demonstrated. Results of a SPDT-switch are shown. Depending on the device periphery the application frequency may easily go beyond 40GHz.

Coplanar Hybrids based on an Enhanced Inductor Model for Mixer Applications up to mm-Wave Frequencies

A designer of up-converters for mm-wave frequencies faces a problem, in that the LO frequency and RF frequency are spaced very close together. Therefore, the suppression of the LO signal is not automatically achieved with the matching networks. In order to suppress the LO signal at the output port, a filter with narrow bandwidth has to be applied or the mixer has to be set up as a balanced mixer. Normally, the second solution is more convenient. A balanced mixer can be set up by utilising 90° or 180° hybrids in conjunction with two identical single mixer stages. These hybrids consist of transmission line couplers or lumped elements. For a high packing density design lumped hybrids are the preferred solution since they utilise less chip area. Circuit design based on coplanar technique offers several advantages compared to microstrip technique as outlined by Pogatzki and Kramer (1). Accurate models for coplanar rectangular inductors which are suitable for interactive CAD were not available for mm-wave frequencies in the past. Therefore, large hybrids like Lange couplers or rat-race couplers were used to achieve the required phase conditions for balanced mixers. This paper introduces an enhanced inductor model based on Naghed and Wolff (2), Naghed et al (3), Kulke and Sporkmann (4), Pogatzki et al (5), which is valid for a wide range of geometries up to mm-wave frequencies and therefore, can be used to design 90° and 180° hybrids. These hybrids require only about 10% of the chip area that standard couplers occupy.