Multi-layer RF filter and balun

摘要

A filter-balun combination for filtering an RF input signal and balancing output RF signals is provided. The filter-balun combination is formed in a multi-layer planar substrate having multiple dielectric layers and multiple planar device layers having conducting material. The filter section includes first and second symmetrical inductors formed in the substrate. The inductors provide filtering for an input signal. The balun section includes a balun central transmission line connected to an output of the filter, and two output structures for providing the output from the filter-balun combination. The central transmission line follows a path through the substrate that includes first and second coil areas. The input line is sandwiched between upper and lower transmission lines in the first and second coil areas. The output of the filter-balun combination is a filtered, balanced signal at each of the two balun output structures.