Antenna concepts for ceramic multilayer modules

LTCC (Low Temperature Cofired Ceramics) dielectrics have a higher permittivity than most of the common organic circuit boards. Combined with their good RF-performance and their nearly arbitrary layer count, these are excellent prerequisites for high packaging density. Thermal conductivity is ten times higher than that of organic substrates, which is very helpful when semiconductors need to be cooled either for power dissipation or for better noise performance at lower operating temperature. The well-established screen-printing process used in LTCC is a further benefit in the volume production of such modules. Over the last decade, low loss LTCC material systems have become available, which are very suitable for microwave and millimetre wave applications. Integrating the antenna into such microwave front-ends is a consequent step in order to avoid phase and amplitude uncertainties associated with connectors and cables. Yet, higher permittivity is not always an advantage. It allows reducing size in some antenna designs, but at the cost of limiting the bandwidth. However, LTCC, with its inherent possibilities of complex three-dimensional structures, facilitates entirely new antenna concepts, which do more than just make up for this drawback. In this paper a few of these solutions for different frequencies and radiation characteristics shall be presented, along with their principle of operation and measured performance.