CMOS voltage-controlled oscillator with high-performance MEMS tunable inductor

Abstract

LC CMOS voltage-controlled oscillators (VCOs) with tunable inductors are essential for high-performance, multi-band communication systems, such as IoT applications and 5G communication. However, VCOs that use CMOS tunable inductors have difficulty in achieving high RF performance due to the low Q-factor of the inductor. In addition, previously reported CMOS VCOs integrated with MEMS inductors have used CMOS switches for tuning frequency bands, but they also had large signal losses on the switch. Herein, we propose a CMOS VCO that is integrated with a MEMS tunable inductor that tunes the frequency band with three MEMS switches. The proposed MEMS tunable inductor enables us to achieve high RF performance due to the suspended structure, and RF MEMS switches enable lower signal loss than CMOS switches. In this work, we successfully fabricated the proposed CMOS VCO integrated with a MEMS tunable inductor using the flip-chip bonding process, and we measured oscillation frequencies according to the actuation of the three switches. The oscillation powers were measured as − 3.03 dBm @ 1.39 GHz, − 5.80 @ 1.98 GHz, − 7.44 dBm @ 2.81 GHz, and − 8.77 dBm @ 3.68 GHz.