Research And Design Of Wireless Communication Systems In Low-power Low-noise Amplifier

This thesis studies and designs the low power low noise amplifier (LNA) of the wireless communication systems. In the RF receiver systems, the low noise amplifier (LNA) is the first stage, which amplifies the useful signal from the antenna. LNA must have low enough noise figure, and also have a certain power gain to enlarge the useful signals, if the LNA can provide big enough power gain, it can depress the noise figure from back stages. So the performances of low noise amplifier directly affect the performance of the entire system.In the circuit designs of LNA, the input matching condition which achieves the minimum noise figure is not equal to the condition which can get the maximum power gain, so it is difficult to realize the simultaneous noise and input matching, thus the circuits often have good power gain and input matching condition, but cannot achieve the theoretical minimum noise figure. Also the low power consumption is required in the wireless communication systems, and if we reduce the power consumption, the performance of low noise amplifier will be deteriorated. In this paper, we will study and design low power LNA to solve the above problems.This paper firstly introduces the basic design theory of low noise amplifiers, including the noise basic theories,the classical noise analysis theory and the requirements of LNA, then discusses several basic topologies, as well as the advantages and disadvantages of these structures.Then this paper has a detailed analysis of various optimization techniques of LNA, especially has a systematic discussion about the low power consumption and the simultaneous matching at input port. This paper proposes an improved optimization method based on the theory of optimization techniques, that can be achieved the simultaneous noise and input matching under low power conditions. A 1.5GHz LNA using improved optimization method is designed under CHRT 0.35μm CMOS processing with Cadence IC 5.0 SpectreRF simulator. The simulation results show that the noise figure is 0.43dB, only 0.04dB higher than the minimum noise figure, input and output have good matching conditions, the gain is 14.6dB, the power consumption is only about 22.4mW. The results verify the design theory.Finally this paper has a discussion of wideband LNA design. It focuses on the analysis of how to design the wideband low noise amplifier using the matching structure of band-pass filter type, particularly on the choice of the filter bandwidth and the application of power constrained noise optimization technique. A 3~5GHz wideband LNA in ultrawideband (UWB) application is designed under TSMC 0.18μm CMOS processing with Agilent ADS2006A simulator, the LNA with about 28mW power consumption achieves the 1~1.3dB noise figure and good input and output broadband matching conditions, and better than 14.6dB power gain with the ripple of 1.7dB.