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

Nur Nur

doi:10.3844/ajassp.2012.1158.1165

Abstract

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.

Highlights

The academia and industry put forth their interest in Ultra Wide Band (UWB) technology because this technology offers a promising solution to the Radio Frequency (RF) spectrum drought by allowing new services to coexist with other radio systems with minimal or no interference (Mir-Moghtadaei et al, 2010)
Power gain: The Low Noise Amplifier (LNA) is required to achieve a high power gain in order to reduce the effect of noise introduced by the subsequent stages at the receiver front end
In our circuit by using both current reuse and shunt-series peaking techniques, the power gain of higher than 17.3 dB is achieved over the entire bandwidth of 2-12 GHz while the peak power gain of 20.352 dB is achieved at the frequency of 7.5 GHz

Summary

INTRODUCTION

The academia and industry put forth their interest in UWB technology because this technology offers a promising solution to the Radio Frequency (RF) spectrum drought by allowing new services to coexist with other radio systems with minimal or no interference (Mir-Moghtadaei et al, 2010). A current re-used cascade amplifier is proposed in (Yousef et al, 2011) which offer a very high gain over a large bandwidth with a reduced noise figure but it consumes large power and suffers from poor linearity. The values of L1 and C1 are chosen in such a way that the effects due to Miller capacitances can be adequately compensated at and transformer is used in (Mehrjoo and Javari, 2011) This topology exhibits very good matching characteristics and consumes low power but its performance is severely degraded at the upper UWB band and it has poor linearity characteristics. It compensates for the low 3-dB bandwidth of the previous stage It further reduces the noise and non linearity at this level with the help of a local active feedback. The proposed LNA exhibits high power gain and linearity making it ideal for implementation in UWB receivers

DISCUSSION

CONCLUSION