Design of Low Noise Amplifiers through Flow-Graphs and their Optimization by the Simulated Annealing Technique

Design of Low Noise Amplifiers through Flow-Graphs and their Optimization by the Simulated Annealing Technique

M. Fakhfakh (University of Sfax, Tunisia), M. Boughariou (University of Sfax, Tunisia), A. Sallem (University of Sfax, Tunisia) and M. Loulou (University of Sfax, Tunisia)
DOI: 10.4018/978-1-60566-886-4.ch004
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Abstract

This chapter presents the optimal design of Low Noise Amplifiers (LNAs). The basic idea consists of optimizing performances of LNAs by a direct action on the scattering parameters. A symbolic approach, namely the Coates Flow-Graph technique, is used to automatically generate symbolic expressions of the impedance parameters and, thus, those of the scattering parameters. The Simulated Annealing optimization technique is applied to determine the optimal sizing of the LNA. ADS simulation results are given to show the viability of the proposed approach.
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A Brief Overview On The Scattering Parameters

The definition of the Scattering Parameters, noticed S-Parameters, is based on the theory of the incident and reflected waves (Kurokawa, 1965; Kurokawa, 1969). Thus, S-parameters describe the relationship between the different waves of a system. Figure 1 represents a network with two ports including the incident and reflected microwaves.

Figure 1.

A two-port network with incident and reflected waves

With (Scott, 1993):

  • a1: the electric field of the microwave signal entering the network input,

  • b1: the electric field of the microwave signal leaving the network input,

  • b2: the electric field of the microwave signal leaving the network output,

  • a2: the electric field of the microwave signal entering the network output.

Therefore, the S-parameters are defined by expressions (1)-(4):

(1)
(2)

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