适用于802.11a的低噪声放大器设计

Design of low noise amplifier for 802.11a application

为实现802.11a接收单元,设计一款适用于802.11a协议具有镜像抑制功能的低噪声放大器（LNA）.电路采用源简并结构,对有源陷波滤波器加以优化,可极大地减小了滤波网络的功耗和芯片面积,提高镜像抑制比,替代传统超外差接收机片外实现滤波器方式.电路采用Jazz 0.18μm SiGe BiCMOS进行工艺仿真,结果表明：在5.15-5.35GHz的工作频段和3.5-3.7GHz镜像频段下,电路可以实现18.52dB的功率增益,小于-13dB的反射系数,3.1-3.4dB的噪声系数和33.75dB的镜频抑制比;5.2GHz频率下的输入3阶交调点为-9.58dBm,电源电压为1.8V,总功耗为13mW,有源滤波器功耗仅为0.57mW.

An image-rejection low noise amplifier（LNA）for 802.11 astandard was designed for realization of 802.11 areceiving unit.This circuit adopted source-degeneration structure with optimization in active notch filter,decreasing the power and die area in filter network dramatically.Image-rejection ratio was increased and traditional super heterodyne receiver with off-chip filter was replaced.Based on Jazz 0.18μm SiGe BiCMOS process,simulation results showed that at the band of 5.15-5.35 GHz and image frequency band of 3.5-3.7GHz,18.52 dB power gain and less than-13 dB reflection coefficient were achieved.Noise figure is 3.1-3.4dB and the image-rejection ratio is 33.75 dB,and the input third-order intermodulation point（IIP3）was-9.58 dBm at 5.2GHz.Total power dissipation was 13 mW draining from 1.8V power supply,and power in active filter was only 0.57 mW.