A monolithic SiGe 5 GHz low noise amplifier and tuneable image-reject filter for wireless LAN applications

This paper presents a monolithic RFIC consisting of a low noise amplifier (LNA) and tuneable image-reject filter (IRF), for wireless local area network applications at 5 GHz. The LNA uses a cascode topology with on-chip matching to provide a simultaneous noise and power match The tuneable third-order filter alters the transfer characteristic of this LNA to achieve filtering of the image signal. The filter is varactor tuned using an external voltage source. The LNA and IRF are designed for operation between 5.15-5.35 GHz, targeted at the lower two bands of the recently allocated unlicensed national information infrastructure (U-NII) frequency bands. The circuit reported here makes use of Motorola's silicon-germanium process technologies.