Micro-fabricated multi-resonant capacitive switch for UWB applications

In this study, a micro-fabricated multi-resonant capacitive switch with high isolation was successfully designed and fabricated for ultra wide band (UWB) system ranging from 3- to 10-GHz. To achieve the high isolation and wide frequency bandwidth, three capacitive shunt membranes and meander inductors were utilized to design the switch with three LC resonant switching circuits. And also, aluminum nitride film (AlN) was applied to increase on/off capacitance ratio of the micro-fabricated capacitive switch. The dielectric constant and tangent loss of the AlN film were 8.8 and 0.008, respectively. The measured on-state and off-state capacitances of each capacitive shunt switch were approximately 52 fF and 3.1 pF. The capacitance ratio was approximately 59. The fabricated resonant switch exhibited the high isolation of over 30dB at the frequencies ranging from 5- to 10-GHz and 70 dB at 6.5GHz. The size and volume of the fabricated switch were approximately 1.4 × 1.7 × 0.0083 (H) mm³.