一种改变交叉耦合极性的新方法

提出了一种用传输线在微带交叉滤波器和腔体交叉滤波器中实现交叉耦合极性改变的新方法。在微带交叉耦合滤波器中运用180°电长度的传输线实现源与非相邻谐振器的耦合,可使交叉耦合极性由容性变为感性。在腔体交叉耦合滤波器中,使用180°左右电长度的传输线,可使传输零点从阻带高端移动到阻带低端。讨论了不同电长度的传输线对交叉耦合的影响,通过调节传输线的电长度,控制传输零点的位置,提高滤波器的带外抑制。这种改变耦合极性的方法,可以用同一耦合方式获得任意位置的传输零点,给滤波器设计提供了更大的自由度。

A new method of changing the polarity of cross-coupling

This paper proposes a new method to implement change of polarity of cross-coupling in microstrip cross-coupling filter and cavity cross-coupling filter by the use of transmission line.To realize the cross-coupling between the source and a nonadjacent resonator by using a transmission line with an electrical length of 180°in microstrip cross-coupling filter,can make the polarity of cross-coupling change from capacitive to inductive.Using a transmission line with an electrical length about 180°in cavity cross-coupling filter,transmission zero can be shifted from upper stopband to lower stopband.A discussion of the effects of different electrical length transmission line on cross-coupling is presented.The positions of transmission zeros can be controlled by adjusting the lengths of transmission lines to improve the rejection level.With this proposed method,transmission zeros can be positioned arbitrarily using the same coupling structure,which makes the filter design more flexible.