Multi-resonant capacitive microelectromechanical system switch with high isolation for ultra-wideband applications

A multi-resonant capacitive microelectromechanical system switch with wide bandwidth and high isolation has been successfully designed and fabricated for ultra-wideband applications. To achieve high isolation and wide operation frequency bandwidth, three capacitive shunt-connected membranes and meander-shaped inductors with several inductances were utilised in serial connection. Moreover, for achieving a large `ON´/`OFF´ capacitance ratio, a high dielectric aluminium nitride (AlN) film was applied. The measured dielectric relative constant and tangent loss of the AlN film were 8.8 and 0.008, respectively. The capacitive switch has the `ON´/`OFF´ capacitance ratio of 59.6 with the measured capacitances of 52 fF and 3.1 pF at `ON´ and `OFF´ states, respectively. The three resonant frequencies were formed at 4, 5 and 6.5 GHz, and the isolation performances were over 30 dB at the frequencies ranging from 5 to 10 GHz and 70 dB at 6.5 GHz. The size of the fabricated switch was ~1.4 × 1.7 × 0.0083 (height) mm³.