微波滤波器的耦合矩阵诊断调试法

Coupling matrix method for diagnosis and tuning of microwave filters

传统的微波滤波器诊断模型构建方法不适用于严格的滤波器综合.提出了一种改进方法,对广义Chebyshev滤波器的传输函数和反射函数分子多项式系数均做了合理限制,继而求出响应对应的耦合矩阵,并与理论综合结果比较,确定出滤波器调试的方向和幅度.最后用该方法分别对四阶开环微带滤波器和八阶波导滤波器进行诊断调试,调试后回波损耗和群时延均满足预期指标,调试时间缩短了一半.

The traditional model-conformation method for microwave filter diagnosis is not suitable for the exact synthesis, so a modified method for the general Chebyshev filter is proposed, i. e. , a reasonable restriction has been imposed on the coefficients of the numerator polynomials in both transfer and reflection functions. Afterwards, the coupling matrix of the filter can be evaluated. Thus the tuning direction and magnitude of corresponding physical structures can be determined by comparison with the designed coupling matrix. Finally, two processes of diagnosing and tuning a four-order microstrip square open-loop filter and an eight-order waveguide filter are demonstrated with the help of the modified diagnosis method, and the response of the filter tuned is fine. The return loss and group delay specification are both achieved, and the consumption of the tuning time is also shortened by a half.