Studies on microwave pulse compression using the nonlinearity of a magnetic material

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The nonlinear and the time domain properties of the microwave propagation in a ferrite are analyzed using a new approach in which the gyromagnetic equation is differentiated in the space and time domains and combined with the finite difference time domain method. The results are as follow. (1) The time domain analysis is carried out on a one-dimensional ferrite waveguide, and it is found that the envelope soliton can be formed for the electromagnetic mode. The soliton evolution simulation is compared with the result by the solution of Schrodinger equation which treats only the signal envelope. (2) Extending the analysis to a two-dimensional model, magnetostatic backward volume wave (MSBVW) mode propagation in a slab waveguide is analyzed. First the frequency characteristics of the transmittance are calculated and compared with the experimental results of a prototype ferrite waveguide. Next the numerical simulations have been carried out for the time domain evolution of a pulse wave, and a nonlinear modification of the field profile is found as well as the nonlinearity in the time domain waveform. (3) Pulse modification is examined under nonuniformly applied bias magnetic fields. (4) Parametric amplification using the MSBVW is analyzed. It is found that the gain characteristics can be enhanced with the appropriate positions of the exciting and the receiving transducers, and that the signal attenuation due to the magnetic loss can be compensated. (5) An MSW mixer based on a new operation principle has been proposed and its characteristics are shown. Though signal mixing using the MSW could not be analyzed by conventional approach, such nonlinear operation has been analyzed in this study. Experimental results are also shown for a prototype MSW mixer.