DC-to-50 GHz compensation structure for flip-chip assembled SPST MEMS switch

A new structure is proposed which simply compensates the flip-chip mounting effect. As an example which shows the mounting effect and the validity of the compensation structure, a discrete RF MEMS SPST switch is used. The degraded frequency response of the RF MEMS SPST switch when it is flipped into a coplanar transmission line is successfully recovered simply by adding the proposed compensation structure. It consists of inserting the proper sizes of CPW series stubs. Whereas conventional wire bonding of discrete MEMS switches in MIC circuits prevents the realization of very low loss characteristics of the switch, models of a flip-chipped MEMS switch show it is possible to retain the low loss characteristics by using some of the novel characteristics of coplanar transmission lines. The principle of achieving such high-quality compensation structure is detailed and is also confirmed by experimental results up to at least 50 GHz. It is shown that a return loss better than 18 dB in the frequency range up to 50 GHz is achievable. Finally, applying this simple compensation structure, the frequency range of operation can be further extended.