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

采用一种新的方法分析了铁氧体中微波传播的非线性和时间特性，该方法将旋磁方程在空间和时间域中进行微分，并结合时间域有限差分法。研究结果如下。(1)对一维铁氧体波导进行了时间域分析，发现在电磁模式下可以形成包络孤子。将孤子演化的模拟结果与仅考虑信号包络的薛定谔方程的解进行了比较。(2)将分析推广到二维模型，分析了静磁反向体积波(MSBVW)模在平板波导中的传播。首先计算了透过率的频率特性，并与原型铁氧体波导的实验结果进行了比较。其次，对脉搏波的时间域演化进行了数值模拟，发现了场分布的非线性修正以及时间域波形的非线性。(3)对非均匀偏置磁场下的脉冲调制进行了研究。(4)对MSBVW的参变放大进行了分析。结果表明，适当的激励换能器和接收换能器的位置可以提高系统的增益特性，并且可以补偿由磁损耗引起的信号衰减。(5)提出了一种基于新工作原理的垃圾混合器，并对其性能进行了分析。虽然传统的方法不能分析使用MSW的信号混频，但在本研究中对这种非线性操作进行了分析。文中还给出了一台原型垃圾混合器的实验结果。

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.