A 4-bit RF MEMS phase shifter monolithically integrated with conventional CMOS

This paper presents the design and characterization of the first RF MEMS phase shifter to be monolithically integrated with conventional CMOS using maskless post-CMOS etching. The phase shifter consists of a micromachined transmission line periodically loaded with 4-bit MEMS digital capacitors, which are controlled using a combination of vertical electrothermal and lateral electrostatic actuation. MIM capacitors are embedded in the transmission line in series with MEMS capacitors to trade tuning ratio for increased capacitor Q. Measured results of the phase shifter at 32 GHz show an average insertion loss of 2.9 dB and a maximum phase shift of 337.5° in 16 steps.