Widely Tunable MEMS LC Tank for Multi-band applications

This paper presents the modeling and simulations of compact multi-band MEMS based LC tank resonator suitable for very low phase-noise VCO. The resonator is based on a high-Q spiral inductor and high capacitive ratio varicap fully integrated in FBK-irst MEMS manufacturing process. The design of the varicap is based on double actuation mechanism with a mechanical central bond that inhibits the pull-in allowing for a theoretically infinite tuning ratio. The measurements show a total capacitance ratio (Cr) of 5.2 with two continuous tuning range with a Cr* = 1.6 and 2.6. The spiral inductor consists of a suspended gold membrane thick 5μm in circular shape. The simulations show that the MEMS based resonator allows for an overall tuning range of 60% in the frequency range 2.15-3.85GHz. Two separate regions of continuous tuning range (9.5% and 30%) allow one to cover the whole frequency spectrum of WiMAX and IEEE802.11a/b/g/n. The simulated quality factor (Q) is about 60. A preliminary design of the MEMS based Voltage Controlled Oscillator (VCO) was performed using Advanced Design System (ADS®). Bonding wire interconnections have been also considered and optimized for improved performance. The VCO prototype is being fabricated on Surface Mount Technology (SMT) on RO4350 laminate.