A Reconfigurable Dual-Frequency Narrowband CMOS LNA Using Phase-Change RF Switches

This paper presents a dual-band low-noise amplifier (LNA) that can be reversibly configured between 3 and 5 GHz using a phase-change (PC) RF switch. Simultaneous noise and conjugate input matching is achieved at the two frequencies using a single PC RF switch and coupled source inductors, thereby minimizing integration complexity and enabling a compact design roughly equal in size to a single-band design. The PC switch has extremely low on-state resistance (1.5– $4\Omega$ ) and parasitic capacitance (12–16 fF), and has a compact footprint ( $\sim 50~\mu \text{m}^{2}$ ). A chip containing the PC switch is fabricated in-house while the rest of the LNA is fabricated in a 0.13- $\mu \text{m}$ CMOS technology. The two chips are combined using an in-house flip-chip integration process. Characterization from five prototypes fabricated in two batches is presented. The integrated LNAs achieved peak gain greater than 20 dB and minimum noise figure less than 2.9 dB in both the frequency bands while consuming a peak power of 7.2 mW from a 1.2-V supply. Comparison of the CMOS-PC prototypes with carefully designed control LNAs demonstrates the effectiveness of the PC switch for RF reconfiguration, which allows the reconfigurable LNA to achieve performance comparable to its nonreconfigurable counterparts.