Noise figure and impedance matching in RF cascode amplifiers

The noise figure in low-noise radio frequency cascode amplifiers using narrow-band input-impedance matching is exhaustively analyzed and accurate equations are derived which fit simulated results well. Moreover, the effect on noise performance of different impedance-matching approaches is discussed and fundamental limitations caused by specific matching networks are pointed out. Finally, an improved matching network is proposed which reduces dominant noise components, greatly improving noise figure. By using the same process parameters, calculations and simulations show that the proposed matching arrangement achieves a noise figure at 0.9 GHz, which is about 0.9-dB better than the state-of-the-art solution.