M. Mayer

Load Pull Characterization of GaN/AlGaN HEMTs

This work presents a large signal characterization of a high power GaN/AlGaN HEMT transistor utilizing a harmonic load pull setup. Two different methods for passive automated tuners have been compared to synthesize the load impedances

A novel low loss microwave multiplexer design based on directional filters

A novel design method for directional filters is presented which reduces transmission loss and insertion loss. The theoretical background of directional filters is given, the frequency characteristics and transmission loss are discussed and parameters responsible for the requirements of a low loss application are worked out. A 50 /spl Omega/ multiplexer was built to act as a bandpass filter bank to separate the fundamental, second and third harmonic frequencies at the input and at the output of a digital audio broadcast (DAB) power amplifier. Finally, measurement results are compared with simulations and the improvements with respect to multiplexers previously presented are pointed out.

Time Synchronization in the Eurobalise Subsystem

The ETCS standard was released by the European Union to reach interoperability in European railway signaling systems. This standard uses so called Eurobalises to send locally stored information to the passing train. Eurobalises are track mounted devices that operate on transponder technology. In order to support the standard for the European train control system (ETCS), a subsystem on the train called balise transmission module (BTM) was developed. The duty of the BTM is to tele-power an Eurobalise as the train passes and to receive the information sent by the Eurobalise. This data has to be demodulated and passed to the European vital computer (EVC), which is the control unit of the locomotive ensuring safe operation. To be able to locate a Eurobalise independent of received telegrams, a Balise Detect signal has to be additionally created by the BTM and sent to the EVC as demanded by ETCS standard. This signal is generated if the received field strength exceeds a given reference level. All components within the ETCS are operating in different time domains. In order to be able to calculate correct timing and odometric data, different time domains have to be synchronized. This has even effect on the safety critical operations within the system. ETCS requires the whole system fulfilling the SIL4 criteria. Considering modularity, it was decided that the BTM has to fulfill SIL4 criteria on its own, too. The crucial aspect is combining safety demands and time synchronization. It affects the communication between the BTM and the EVC. This paper focuses on the synchronization mechanisms within the components of the BTM and the synchronization between BTM and EVC.

Analysis of RF-Power Amplifier Modeling Performance using a 16-QAM Modulation over AWGN Channels

This paper presents the black-box modeling of a microwave power amplifier (PA) and its performance in the nonlinear operation region - low input back off (IBO). As input signal a rectangle 16-QAM corrupted by different levels of additive white Gaussian noise (AWGN) was used. The nonlinearities caused by the amplifier in low IBO operating conditions can change the output constellation and lead to difficulties in finding the correct model parameters, as the black-box identification procedure is based on measured input/output signals. These signals can be altered by different types of noise. The AWGN degrades the signal to noise ratio (SNR) and can lower the model accuracy that should ideally not be influenced. In this paper the models were first estimated using noise-free data (NFD) and secondly with different levels of noisy corrupted data (NCD). NFD was also applied to the models calculated with NCD and vice versa. An investigation of the loss of accuracy caused by the noise in the identified models is presented. Three situations were considered: 6dB IBO, 4dB IBO, and 2dB IBO. It is shown that the pseudo-inverse based models present reasonable results for PA modeling when AWGN is incident

The Eurobalise subsystem — a technical reflection

This article focuses on the Eurobalise Subsystem that is part of the European train control system ETCS, which enables interoperable rail traffic all over Europe by a standardized track and train equipment (ERTMS/ETCS). Based on an example implementation the critical points of the standard are pointed out and solutions are discussed. Concepts for an easy application in the train as well as transmitter and receiver solutions which fulfill the high safety standards for railway equipment are shown.ZusammenfassungDieser Artikel beleuchtet das Eurobalisen Subsystem, welches ein Teil des europäischen Zugsicherungs-systems ETCS ist. ETCS ermöglicht durch standardisierte Strecken- und Fahrzeugkomponenten interoperablen Zugverkehr in ganz Europa. Anhand einer Prototypimplementierung werden die kritischen Aspekte des Standards und mögliche Lösungsansätze diskutiert. Darüber hinaus werden Konzepte für eine einfache Anwendung im Zug und Lösungen für die Sende- und Empfangseinheiten, welche die hohen Sicherheitsanforderungen im Bahnbereich erfüllen, gezeigt.

Design of a Brewster-angle broad-band waveguide window with ghost-mode suppression for the Ku-band

SummaryA broad-band waveguide window for the Ku-band using Brewsters angle is shown both theoretically and experimentally to suffer from a ghost-modes interference. From the knowledge of the field distributions, the ghost-mode can be suppressed by short circuits which do not hamper the transmission of the fundamental waveguide mode. Experiments prove the principle.ZusammenfassungTheoretisch und experimentell wird nachgewiesen, dass ein breitbandiges, mit dem Brewster-Winkel eingebautes Hohlleiterfenster durch Geisterwellen beeinträchtigt wird. Aus der Kenntnis der Feldverteilungen heraus können die Geisterwellen durch Kurzschlüsse, welche den Wellendurchgang nicht beeinflussen, unterdrückt werden. Experimente belegen die prinzipielle Wirkungsweise.

Messmethoden zur Charakterisierung von Mikrowellenleistungstransistoren

ZusammenfassungZum treffsicheren Entwurf von Mikrowellenleistungsverstärkern ist es unumgänglich, das physikalische Verhalten der verwendeten Bauelemente möglichst genau und vollständig zu kennen. Besonderes Augenmerk ist dabei auf das zentrale Element dieser Schaltungen, den Leistungstransistor, zu legen, der durch seine nichtlinearen Eigenschaften das Verhalten des endgültigen Verstärkers wesentlich beeinflusst. Dieser Artikel zeigt im Überblick aktuelle Methoden zur messtechnischen Erfassung dieser Eigenschaften. Im Weiteren wird ein Messystem vorgestellt, mit dem das Verhalten eines Leistungstransistors in einem Frequenzbereich von 30 kHz bis 8,7 GHz bei Biasströmen bis zu 7,5 A unter Berücksichtigung der Eigenerwärmung ermittelt werden kann.AbstractFor first try designs of microwave power amplifiers it is necessary to know the entire physical behaviour of the used components with high accuracy. The attention should be directed especially to the center component of these circuits, the power transistor, whose nonlinear characteristics have an essential impact on the behavior of the whole amplifier. This article gives an overview of current methods of measurement for microwave power transistor characterization. Furthermore a measurement system is presented, capable of characterizing microwave power transistors within a frequency range from 30 kHz to 8.7 GHz at bias current up to 7.5 A including self heating effects.