A CMOS variable gain LNA for UWB receivers

A CMOS variable gain low noise amplifier (LNA) is presented for 4.2-4.8 GHz ultra-wideband appli- cation in accordance with Chinese standard. The design method for the wideband input matching is presented and the low noise performance of the LNA is illustrated. A three-bit digital programmable gain control circuit is ex- ploited to achieve variable gain. The design was implemented in 0.13- m RF CMOS process, and the die occupies an area of 0.9 mm 2 with ESD pads. Totally the circuit draws 18 mA DC current from 1.2 V DC supply, the LNA exhibits minimum noise figure of 2.3 dB, S.1;1/ less than -9 dB and S.2;2/ less than -10 dB. The maximum and the minimum power gains are 28.5 dB and 16 dB respectively. The tuning step of the gain is about 4 dB with four steps in all. Also the input 1 dB compression point is -10 dBm and input third order intercept point (IIP3) is -2 dBm.