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一、前言宽频带超高频通讯机中所用可调滤波器,多半是分段设计的,主要是因为通常使用的耦合元件的耦合系数是随频率的升高而加强的函数。例如,在使用电感耦合元件时,耦合系数k与频率f的1.5次或2次方而变化。将设计好的滤波器由低频向高频调整时,滤波器的三分贝带宽与频率成1.5次或2次方的比例而加
I. INTRODUCTION The tunable filters used in wideband UHF communication systems are mostly segmented designs, mainly because the coupling coefficients of commonly used coupling elements are a function of increasing frequency. For example, when an inductive coupling element is used, the coupling coefficient k varies with 1.5 times or twice the frequency f. When the designed filter is adjusted from low frequency to high frequency, the ratio of the filter’s three dB bandwidth to the frequency is 1.5 times or 2 times