Blocker filtering low-noise amplifier for SAW-less Bluetooth receiver system

Abstract

A 2.4 GHz CMOS blocker filtering low-noise amplifier (BF-LNA) suitable for Bluetooth™ application is presented. The circuit employs a differential amplifier topology with a current mirror active load and a notch filter. Each path amplifies differentially with the common mode input signal, but there is a notch filter rejecting only the wanted signal at one path. By subtracting the two signals from each path, the large interferers are rejected and only the wanted signal is amplified. Therefore, it becomes a narrow-band amplifier with blocker filtering capability, realizing a receiver system without need of the off-chip SAW filter. The BF-LNA is designed using a 0.13-μm CMOS process. The measured performances are a gain of 11.4 dB, and a noise figure of 1.85 dB. Attenuation levels at 400 MHz apart from the target frequency are −13 and −29 dBc at each sideband. The P1dB,in and IIP3 are −8.2 and 1.46 dBm, respectively. The proposed BF-LNA can reject large interferers at the front-end of the receiver system with a good noise figure.