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 3rd LO harmonic. This is important for the coexistence of cellular systems with e.g. WLAN 802.11a operating in the 5GHz band.