传输矩阵法在行波管内部反射引起的增益波动计算中的应用  

Application of transfer matrix method to calculating th effect of multiple internal reflections on the small signal gain ripple of TWT

作　　者：易红霞[1] 肖刘[1] 苏小保[1] 

机构地区：[1]中国科学院电子学研究所,北京100190

出　　处：《物理学报》2016年第12期296-306,共11页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:61401427)资助的课题~~

摘　　要：本文分析了由于行波管慢波结构制造误差引入的多个不连续点对小信号增益的影响.行波管内部反射对增益波动的影响,须采用考虑反射波的四阶模型进行分析,用传输矩阵法对节点处的自左至右入射和自右至左入射两种散射类型建立传输矩阵,研究在不同空间电荷参量下,慢波电路的单个反射节点以及慢波电路的皮尔斯速度参量b和增益参量C的多个随机分布不连续性对行波管小信号增益的影响,计算结果与Chernin模型具有很好的一致性.并以G波段行波管为例分析了慢波结构周期长度分布有两个不连续点和周期长度的多个随机分布不连续性带来的小信号增益波动.结果表明,制造误差越大,周期长度分布的两个不连续点相距越远,小信号增益波动越大,多个小的不连续性可以引起较大的增益波动.The low-signal-gain versus frequency slope is often a highly desirable property of traveling wave tube （TWT） used in a communication system. The gain ripple is usually caused by internal reflexions of forward and backward waves in the TWT. Random fabrication error may have a detrimental effect on the performance of TWT. The quartic equation including backward wave models the effect of reflection to analyze the effect of Gain ripple from many small circuit errors in a TWT operating under small-signal condition. We present a transfer matrix method （TMM） to correctly calculate the transmission and reflection of the wave incident respectively from left and right at a single isolated joint. The TMM, which links the input signal to output signal that includes the feedback signal from the reflections at multiple joints to the output end, can calculate the gain ripple of multiple internal reflections. Appling this method to several numerical examples, we look at how small signal gain is affected by a single isolated discontinuity and many small randomly distributed discontinuities. In particular, we investigate the effects of random perturbations of Pierce velocity detuning parameter b and Pierce gain parameter C on the small signal gain at different values of space charge 4QC . The computed result agrees with that from Chernin＇s model. We find that reflections may significantly increase the statistical effects on the gain. A further conclusion is that the standard deviation of gain, σdgain, increases with σb gradually, but the ratio of the backward wave power to the forward wave power at x=0 decreases with σb when standard deviation of pierce velocity detuning parameter, σb, is more than 1.5. In another example, the effects of two discontinuities of pitch distribution and many small random pitch errors on gain ripple are reported for a G-band TWT. We find that larger pitch error and longer distance for the discontinuities may produce a larger ripple in the small-signal-gain versus frequency. Many small dis

关 键 词：传输矩阵法 小信号增益 反射 行波管 

分 类 号：TN124[电子电信—物理电子学]