A tunable gain and tunable band active balun LNA for IEEE 802.11ac WLAN receivers

Abstract

A tunable gain and tunable band low-noise amplifier (LNA) for IEEE 802.11ac WLAN standard is proposed, with low noise figure and high linearity. The LNA is based on an active balun cascode topology with buffered negative feedback to achieve a differential signalling at the output. The unique feature of the proposed LNA includes highly linear, continuously tunable gain from 3 dB to 23 dB, in addition to a tunable frequency band from 4.5 GHz to 5.5 GHz, while meeting other critical LNA parameters such as noise figure and third order input inter-modulation point (IIP3). Tunable gain is achieved with the help of active CMOS resistors (ACR) at the core LNA load and also in the active negative feedback path, while tunable frequency band is achieved by a tunable LC tank load. The buffered negative feedback with cascode active balun provides the low noise figure and competitive IIP3. The LNA is implemented in 1.2V, 65nm CMOS technology. Measured LNA performance shows a noise figure of 2 dB and IIP3 of -6.5dBm at the highest gain of 23 dB and a noise figure of 6 dB and IIP3 of +10dBm at the lowest gain of 3 dB. The active chip area of the LNA is 0.043mm2 with a moderate power consumption of 16mW.