Analysis of Transmission Line Models with Non Linear Elements for Opposite Phase and Group Velocities

Abstract

The use of nonlinear transmission lines in microwave engineering has been increased tremendously in recent years. They find extensive applications in high power microwave generation shaping a broader pulse to narrow pulse in the realization of metamaterial and so on. A nonlinear transmission line comprises a transmission line periodically loaded with varactor diodes. The nonlinearity in the transmission lines comes from the nonlinear capacitance of the varactor diode. In literature most of the nonlinear transmission lines are designed with the help of varactor diodes. newlineBecause of the recent advances in the inductor design at high frequencies on microstrip realization the use of inductors at microwave frequencies increased considerably. Hence the nonlinear transmission lines can also be realized using the nonlinear inductors at high frequencies. This thesis aimed at theoretical analysis of the conventional transmission line models with a nonlinear inductor and nonlinear capacitors. newlineIn this thesis the capacitor and inductor are assumed to be nonlinear in their constitutive relationships. Initially the frequency response of the nonlinear element is obtained in the time domain and frequency domain. Then the uses of these elements in the conventional transmission line models are analyzed with the main emphasis on phase velocity and group velocity. The main requirement of this thesis is to analyze the transmission line models with opposite phase and group velocities. newlineThis thesis presents the behavior of different transmission lines with different combinations of nonlinear elements and presents the general conclusion of nonlinear transmission lines with the help of nonlinear inductors. Along with this this thesis also presents a simpler equivalent circuit model to obtain opposite phase and group velocities. newline newline newline