A novel tunable water-based RF MEMS solenoid inductor

This paper proposed a novel tunable MEMS solenoid inductor. This tunable solenoid inductor benefits from a liquid-injected core which varies the permeability of the core corresponding to the level of injection of the liquid; hence, the change in permeability of the core causes the change in the inductance. In this work, HFSS is used for 3D EM simulation. The proposed Solenoid inductor is simulated in Silicon substrate with Copper metal as the coil and injected salted water (CaCl₂ solved in water) as the solenoid core. The similar previous works for tunable MEMS inductor employing ferromagnetic cores and liquid-based spiral inductors could not exceed an operating frequency of 2 GHz and a Q factor of 12. Here, a maximum Q factor of 18 and tuning range of 60% were achieved at 18 GHz. Also, the implementation procedure of the proposed variable solenoid inductor is simpler and more cost-effective than the other works.