Bandwidth Analysis of a Broadband Amplifier with Two-Stage Matching System Using the Smith Chart

Abstract

This paper describes a novel trace structure for the analysis and design of two-stage Broadband Frequency Low Noise Amplifiers based on standard Smith chart procedures and program algorithm realization. The method allows to put the transistor's S-parameters and details of the source and load networks and to interactively explore the effects of these quantities on design variables such as gain, noise figure and stability. It also facilitates the design of two-element matching networks to transform the source and load impedances to optimum values to achieve the desired gain and noise performance. The extended Smith chart concept is proposed to enable the advanced graphical interpretation of devices containing complex properties. This methodology is based on the Smith chart concept, and makes it easy to deal with devices containing signal sources, nonlinearity, very high Q factors and negative resistances. The concept of explaining the use of the Smith chart in combination with using modern tools as MATLAB scripts is exemplified in graphical forms. Phyton-based program contains the algorithm for parameters calculation. It explains the procedure that must be used to solve the two-stage impedance-matching problem. The point of this proposal is using of Smith chart plane for the graphical processing for its application to oscillator analysis. To demonstrate the effective usage of this methodology an interpretation and analysis of the oscillator, especially in terms of gain, noise and stability, are provided. The practical relevance concludes results of multistage design using impedance matching LC networks for the intersection level. The values of the parameters of the integrated microcircuit confirm the possibility of using the calculation methodology considered in the paper. The proposed solution is validated with extensive RF measurements at 3.5 GHz and is benchmarked against several frequency ranges for noise, stability and gain values. The methodology shown in the paper can be used in the development and design of modern microwave amplifiers, as well as for research and analysis of the efficiency of existing devices.