Design and construction of a broadband fixture for high power devices

3 Introduction During the last decade, the technological environment has experienced an impressive growth in wireless communications. Applications like Digital Terrestrial Television (DTT), UMTS, GPS and WLAN modules are only few but important examples of the rise and the spread of this kind of technology. The constant request for improving performances of these applications, is often transposed into efforts devoted towards research into developing smaller active devices that meet higher power, higher linearity and lower noise requirements. Designers have to face more stringent specifications, given by customers and regulating agencies, and the need to reduce the time to market. In this scenario, traditional empirical methods based on experience and measurements or the ‘cut and try’ approach have become inefficient. Consequently the success of design techniques based on the use of modern CAD, such as ADS by Agilent and AWR Microwave Office has increased. Such programs allow the performance simulation of transmission line circuits with a good level of confidence if accurate models to simulate the behavior of the devices are provided. A lot of effort has been dedicated to improving the fidelity of such models in order to reduce the gap between the design expectations and the circuits produced. These models are obtained by a device characterization process, performing a set of measurements, operated in appropriate benches, for extrapolating some parameters that describe the transistors. The accuracy and the repeatability of these measurements hence represent the basic step for modern RF and Microwave designs.