Design Challenges and Performance Parameters of Low Noise Amplifier

Wireless communication system is an integral part of day today communication. For effective wireless communication, faithful transreceiption of the signal is required. It can be achieved by careful design of the receiver circuit. Hence there is wide scope of improvement in different blocks of the receiver. LNA is the first block of any receiver in communication system. At the receiver side in communication link weak signal should be amplified for further processing at minimum noise level. Amplification of weak signal and attenuation in noise level is a key role of LNA. LNA design meets different challenges because of its simultaneous requirements like good transistor selection, suitable DC biasing network, high gain, low noise figure, good input-output matching circuits, high linearity and good stability. All these design parameters are equally important and always independent on each others. To simplify the design and analysis of analog circuits, it is useful to abstract circuit blocks into two-port networks. System analysis for two port network can be achieve using Impedance (z), Admittance (y), Hybrid (h) or Scattering parameters (s). Scattering parameters (s) are more applicable at RF due to its ability to express in terms of powers, are suitable for high frequencies and possibility of complete transmission. This paper highlights the design challenges, performance parameters or all the necessary steps for LNA design. IndexTerms-ADS(Advanced Design System), Conditional Stability, Impedance Matching, LNA(Low Noise Amplifier), Smith Chart, S-parameters.