Single-ended low noise multiband LNA with programmable integrated matching and high isolation switches

This paper describes a novel 90nm single-ended multiband input LNA preceded by RF input switches connected to an on-chip balun intended to drive a differential mixer. The architecture achieves a low noise figure of 1.8dB. The advantage with the proposed architecture is that it is fully single-ended with on-chip programmable narrow-band matching eliminating the need of off-chip components. Especially in multiband integrated radios a single-ended LNA is highly desirable since the pin-count for the LNAs is reduced by half compared with a differential architecture. The PCB routing of the RF input signal is simplified. Narrow-band matching is advantageous compared to common broadband matching since this adds attenuation of out of band interferers and suppresses conversion of 3^rd LO harmonic. This is important for the coexistence of cellular systems with e.g. WLAN 802.11a operating in the 5GHz band.