The Research And Design Of Dual Band Low Noise Amplifier

Thanks to the wireless communication system's fast developing,RF receiver is developing towards the miniaturized,highly integrated and high frequency selectivity direction,and showing the situation that coexistence of multiple criteria and multiple frequency bands.The multiple criteria and multiple working systems promote the study of low noise amplifier,which can work simultaneously in multiple frequency point.Based on the fundamental theory and analysis method,here two different kind dual-band low noise amplifiers are proposed: concentrated parameters of dual-band low noise amplifier and the distribution parameters of dual-band low noise amplifier.The specific content can be described as below:First of all,having finished a large number of theses and articles,the history and present research situation of low noise amplifier are reviewed and summarized,several main existing scheme of multi-band LNA are also introduced.Then this paper explains the performance index definition of the low noise amplifier and its implementation scheme,how to design an amplifier according to the specific requirements of the gain,noise figure and bandwidth.This chapter provides the essential theory basis for the design of the dual band low noise amplifier.Secondly,a dual-band low noise amplifier is devised by adopting lumped parameters method,its working frequency is 900 MHz and 1.8GHz.The dual band low noise amplifier is built by Avago's ATF54143 transistor,and the design can divide into two parts: one part is the DC bias circuit design,it is constructed after selecting the appropriate static working point.The other part is the matching circuit design,the frequency selective network can be achieved by using of discrete components on the basis of LC resonant circuit's transmission characteristics.After that,the entire amplifying circuit is simulated in Advanced Design System.The physical production and test results demonstrates the effectiveness of the implementation scheme.The amplifier that we design is working at 900 MHz and 1.8GHz,return loss of input and output is bigger than 10 dB,the gain is larger than 21 dB,the noise figure is less than 1dB.Finally,we propose another dual-band low noise amplifier by the method of distributed parameter,and its working frequency is 1.8GHz and 2.4GHz.The DC bias part still use the circuit that we have designed in the third chapter.The design of matching circuit can be distributed to microstrip frequency selective circuit,input and output microstrip circuit.Among them,the microstrip resonant circuit uses stepped impedance resonator(SIR)structure to achieve.Smith chart is taken into input and output impedance matching design.Then we use ADS software to simulate the amplifying circuit.After physical production and physical test,The results show that a single dual-band low noise amplifier's performance indexes are as follows: input and output return loss is more than 10 dB,the gain is larger than 12 dB,the noise figure is less than 1.5dB.More research and improvement is needed in the cascaded dual-band low noise amplifier in the future.