At present, there are still two important trends to be observed in the development of complex electronic systems, namely miniaturisation of components and integration of multiple functional modules into one device. The goals are to achieve more mobile and even portable systems which are less expensive at the same time and to implement di®erent sensing or actuating functions, respectively. In this perspective the growth of dielectric, piezoelectric, pyroelectric and ferroelectric materials in the form of thin ¯lms has attracted a lot of attention in the last years. Practical applications for mobile communication systems are for example miniaturized antenna duplexers, multiplexers for cellular base stations and voltage controlled oscillators. The continuous growth of wireless communication networks is causing an ever increasing crowding in the herztian spectrum and it is quite intelligible that a high demand for increased bandwidth exists in order to allow for an accurate transmission from one device to the other. The market volume of cellular and cordless phones is immense and new markets of technically similar products, e.g. Bluetooth, wireless local area networks (WLAN), systems including navigation are emerging today. All these products have in common that they rely on key-functional elements such as high-frequency ¯lters, ampli¯ers, mixers and antennas. Combining ampli¯ers and ¯lters into an integrated package would be the ideal solution to make wireless phones smaller, lower cost and more smart.weiterlesen