Image rejection low noise amplifier for WLAN 802.11a application

This paper presents a novel low noise amplifier (LNA) topology with image rejection (IR), called IRLNA. It achieves a high IR ratio using on-chip inductors with low quality factor. Two IRLNAs based on a standard 0.18-μm CMOS technology are designed with L- and π- resonant network, respectively. They have the same power consumption of 8 mW with one 1.8 V power supply. At the signal frequency of 5.25 GHz in the band of WLAN 802.11a, and with the image frequency at 3.25GHz, the simulation results show that the IR ratios achieve 71dB for L-resonant network and 92dB for π-resonant network with on-chip inductors, and their noise figures are 1.4 dB and 1.7 dB, respectively.