A 3-5GHz frequency tunable ultra wideband LNA for OFDM applications

In this paper, a frequency tunable differential input differential output low noise amplifier (LNA), used for 3-5 GHz OFDM applications, is proposed and analyzed. The LNA has a wideband input matching and a tunable output matching. The digital controlled capacitor arrays in the output matching networks allow the LNA to be switched smoothly in the frequency range of 3 to 5 GHz with output return loss less than -15 dB. The overall LNA is designed with TSMC 0.18 mum technology, and the simulation result shows that the input return loss is less than -12 dB and the noise figure is less than 4.5 dB in desired frequency range. At 3.3 V power supply, the LNA achieves an 8-12 dB transducer gain in the frequency range with the power consumption of only 20 mW.