任意节数切比雪夫阶梯阻抗变换器的计算机辅助设计

THE COMPUTER AIDED DESIGN OF CHEBYSHEV STEPPED IMPEDANCE TRANSFORMER WITH ARBITRARY SECTION NUMBERS AND ARBITRARY IMPENDANCE RATIO

已经发表的切比雪夫阶梯阻抗变换器设计的严格公式和数表仅适用于N≤4节,本文由网络级联理论,利用计算机辅助设计对任意节数、任意阻抗比和任意带宽的切比雪夫阻抗变换器实现了最佳综合。当给定阻抗比尺、带宽 W_q 和带内最大驻波比ρ,程序即可确定变换器所需的节数和各节的阻抗值。利用这个方法,本文计算给出了5—8节这种阻抗变换器的详细设计数表,并计算了所综合的变换器的特性与标准切比雪夫响应的偏差,结果表明,两者符合得很好,比已有文献的结果更精确或至少相当,最后还讨论了各节阻抗值精度对变换器性能的影响.

Although data on the Chebyshev stepped impedance transformer are widely ■tsted in literature,accurate design formulae and tables are available only for N≤4,thus necessitating various approximations for other cases.In this paper, the reflection is calculated rigorously for a cascade network which consists of sections of arbitrary numbers and transfoms an arbitrary impedance.A general purpose computer program is thegn written to ootimize the whole structure in the sense that the frequency depedance of the reflection is a Chebyshev one. As a result,for any given impedance ratio R and any specified VSWR over a specified bandwidth,the section number N and the impedance of each section can be obtained easily and accurately. In this paper,detailed design tables obtained by using this method for N=5 to 8 are given.We also use the computer program to calculate the deviation of the synthesized performance from the Chebyshev one.The results show that it agrees well with the latter.Comparod with the results given by previous methods,they turn out to be better,or at least equally good.Finally, the influence of each impedance accuracy upon the performance of the trans- former is discussed