高功率脉冲技术领域的变阻抗传输线研究

As the pulsed power of a pulsed power system grows higher and higher, radial impedance transformers are usually needed to combine the the outputs from many pulsed accelerators to a load. The non-uniform transmission lines had been entensively investigated in the field of microwave transmission. However, the results obtained in the field of microwave transmision were based on the analysis of tranferring continuous sine waves and it is not known yet whether these results are applicaple to the non-uniform transmission lines used in the field of pulsed power technology where a single pulse is transferred. Aiming at this problem, the non-uniform transmission lines transferring a single pulse will be investigated by theoretical analysis, electric circuit simulation, electromagnetic field simulation and experiment. The investigation will be focused on the efficiency of the power transfer as well as its optimization. The main factors influencing the efficiency of the power transfer will be determined. The power transfer for the non-uniform transmission lines with different impedance profile will be compared and the reasons for the difference in the power transfer will be analysed. All the above mentioned research will be helpful in understanding the power transmison of the non-uniform transmission lines along which a single pulse is tranferred, and helpful in extending the knowledge of non-uniform transmission lines to the field of pulsed power technology.

随着脉冲功率系统功率的不断增大，人们通常采用径向变阻抗传输线将多台脉冲加速器的功率汇聚到负载上，并达到阻抗变换的目的。以往对变阻抗传输线的研究主要集中在微波通讯领域，其研究结果几乎都是在连续正弦波的基础上分析得到的，尚不清楚这些结果能否适用于脉冲功率系统中的变阻抗传输线。针对这个问题，本项目拟对单脉冲波形驱动下的变阻抗传输线进行理论分析、电路模拟、电磁场模拟和缩比实验，着重关注径向变阻抗传输线的功率传递效率及优化方法，研究影响功率传递效率的主要因素，比较不同线型的变阻抗传输线的传输特性并分析其差异的原因。这些研究工作将有助于了解单脉冲波形条件下变阻抗传输线的功率传输特性，有助于将现有的变阻抗传输线理论拓展到脉冲功率技术领域，促进脉冲功率技术的发展。

提出了一种变阻抗传输线电路模拟的分段方法–等阻抗分段法。相对于通常使用的等长度分段法，等阻抗分段法所需的分段数减少并且收敛速度加快。通过电路模拟，发现指数线的功率传递效率高于高斯线，并基于傅立叶频谱分析和变阻抗传输线的高通特性，对此结果进行了解释。基于多段级联变阻抗线电路模型，推导了适用于任意线型变阻抗线输出电压的解析解，其结果和Pspice电路模拟的结果完全一致。对该解析解进行数学推导，从数学上证实了变阻抗线的首达波特性、脉冲压缩特性和高通特性。对指数型、高斯型、线性线和双曲线等变阻抗整体径向传输线(monolithoic radial transmission line: MRTL)进行了三维电磁场数值模拟，结果表明指数线的功率传输效率是最高的。但是，不论何种线型，电磁场模拟得到的功率传输效率比电路模拟得到的至少低15%，这说明电路模拟的基础假设（电磁波以准TEM模传播）是不正确的。另外，研究了驱动源数目、首末端阻抗、变阻抗线型、开孔等对MRTL功率传输效率的影响。若综合考虑功率传输效率和实际加工安装，双曲线型MRTL是最佳选择。设计和研制了MRTL的缩比实验模型。利用脉冲形成线技术和匹配电阻网络分路器，产生20路方波脉冲（30V、10ns），同时从外圆周驱动双曲线型的MRTL，从MRTL圆心处向匹配负载输出脉冲电压。基于上述MRTL的缩比实验模型，进行了MRTL缩比实验。实验得到的输出电压波形和三维电磁场数值模拟得到的电压波形完全重合，说明三维电磁场数值模拟结果是正确的。当输入电压为方波时，输出电压明显畸变，基于变阻抗线的高通特性对此畸变进行了解释。实验研究了多路输入故障模式（某些路短路或开路、各路注入时间分散性）对输出电压的影响。