对Cohn直耦滤波器理论的推广

本文把Cohn的直耦滤波器理论推广到四分之一波长耦合滤波器,从而使这两种类型的微波滤波器在理论上统一起来。给出了低通到带通的频响变换式,这个变换式考虑了滤波器电纳随频率改变。实验结果表明,应用导出的设计公式进行设计,预示的带宽和阻带衰减更接近实际。最后,对频响特性不对称性的消除方法进行了一些讨论。

A DEVELOPMENT OF COHN'S THEORY ON DIRECTLY COUPLED RESONATOR FILTERS

In this paper Cohn's theory on directly coupled resonator filters is extended to one-quarter-wavelength coupled filters, thus theoretically unifying the two different types of microwave filters. The frequency response transformation from a lowpass to a band pass filter is given, the change of the filter susceptance with frequency being taken into account. Experimental results show that, using formulas derived in this paper for filter designing, the expected bandwidth and stop-band attenuation are in better agreement with practice. Finally, a method for eliminating asymmetry in frequency characteristics is discussed.