RF MEMS Switches

RF MEMS devices developed at CSIR CEERI have shown great potential in strategic, mobile and medical applications. The compact, lightweight (micrograms) and highly energy efficient devices can be used in earth-bound communication stations (in Satellite Payloads), hand-held communication systems, missile communication or smart munition (in RF front ends for communication), medical diagnostics (in MRIs for Digital micro-switching to achieve Zero TE images) and mobile phones (Switch matrices and signal switching networks). Existing solid-state devices consume large power even in OFF state resulting in poor performance and coaxial switches are bulky and need large surface area. RF MEMS switches are hybrid miniaturised devices which have small size, low power consumption, and good RF response. Hence, RF MEMS have shown a great market potential of the order of billion dollars. CSIR-CEERI developed a wide range of RF switches (Fig. 1) that include capacitive (a), Ohmic (b), SPDT (d), SP4T (f) and various advanced hybrid SPDT (e) configurations. In accordance, the design and development of phase shifters (c) were also explored.

The capacitive RF switches have been developed for X & Ku-band communication applications. The size of a switch is reduced by the development of advanced dielectric materials like HfO2. For low frequency application in the DC-X band, Ohmic switches have been developed. Power and current handling capability are improved by the development of innovative materials like Ni-Au alloy and composites. Subsequent to the unit switch design, SPNT switch matrix has been developed.

Fig. 1: (a) Capacitive type MEMS switch, (b) Ohmic type MEMS switch, (c) 3-Bit DMTL Phase Shifter, (d) Ohmic Based SPDT Switch, (e) Hybrid SPDT Switch, (f) Ohmic Based SP4T Switch

Application Areas of RF MEMS Switches (Fig. 2)

Fig. 2: (a) Block Diagram of Satellite Payload; Green boxes are targeted areas where conventional switches can be replaced by RF MEMS switches or switch matrices. (b) MRI Scanner Cutaway; Control of switching between RF Coils ( X, Y & Z direction) can be done using ultra fast MEMS switches. (c) Smart Munition Control. Surveillance of missile activities can be done using smart MEMS circuits and accordingly action can be taken up