Improved performance of flip chip assembled MMIC amplifiers on LTCC using a photonic bandgap structure

Further cost reduction in today's microwave frontends is strongly related to assembly technology as well as module technology. Depending on the particular mix of technologies, specific problems and chances can he addressed. In case of tlip-chip on LTCC, various effects of performance degradation of tbe MMICs can be observed, some of which can be related to unwanted internal coupling of the microstrip IC due to the floating groundplane. For some MMICs a periodic structure below the chip can help to improve the characteristics of the assembled chip due to its ability to suppress a particular class of unwanted modes behveen the chip groundplane and the module ground. The periodic structure is proposed and measured results are given and discussed.