A 2-12 GHz Low Noise Amplifier Design for Ultra Wide Band Applications

Problem statement: The Low Noise Amplifier (LNA) is a core block of an Ultra Wide Band (UWB) receiver since it amplifies a very weak signal received at the antenna to acceptable levels while introducing less self-generated noise and distortions. The LNA design poses a unique challenge as it requires simultaneous optimization of various performance parameters like power gain, input matching, noise figure, power consumption and linearity over the entire UWB band. Approach: In this study, a three stage LNA is proposed with a resistive current reuse network as a first stage, a cascode amplifier with shunt-series peaking and a local active feedback as a second stage and a voltage buffer as a third stage. A resistive current reuse network is used to achieve better linearity, low noise figure, better input matching with lesser power consumption. A cascode stage with shunt-series peaking and a local active feedback is used to enhance the bandwidth and reverse isolation. A voltage buffer is used as an output stage to achieve better output matching. Results: The proposed LNA is designed using 0.18 µm CMOS technology and is simulated to verify its performance. It achieves a power gain of greater than 17.3 dB, a noise figure less than 2.45 dB with an input matching less than -11.2 dB over a 3-dB bandwidth of 2-12 GHz. The achieved output matching is below -12 dB, the reverse isolation is below -68 dB with a Rollet’s stability factor is greater than 1000 to ensure better stability. This LNA also ensures better linearity with an IIP₃ of 3 dBm at 7.5 GHz with low power consumption of 10.7 mW. Conclusion/Recommendations: From the simulation results it is evident that the presented LNA claims the advantages of very high gain, better input matching with low noise figure and less power consumption.