Fabrication and modeling of an SP3T RF MEMS switch

Most of the research effort on RF MEMS switches reported in the literature has been directed toward the development of single-pole-single-throw (SPST) switches. The SPST switch is a two-port device, which acts as a simple RF relay. In today's communication systems, switches are typically used in the form of switch matrices. The use of multiport switches as the basic building blocks can considerably simplify the integration problem of large switch matrices. In our knowledge, very limited work has been reported on integrated multiport MEMS switches. We present a novel integrated SP3T MEMS switch. RF simulation, along with circuit modeling, is used to design the switch. Three beams with narrow-width tips are integrated on top of a coplanar transmission line. The junction where the three beams interact is inherently a wide band junction, which makes it possible to design a wideband SP3T switch with 30 dB isolation up to 20 GHz. Theoretical and measured results demonstrate the validity of the proposed design. Even though the concept is demonstrated using flip-chip technology, the SP3T switch can potentially be realized by integrating the beams and the substrate on one chip.