A Miniaturized Conductor-Backed Slot-Line Resonator Filter With Two Transmission Zeros

In this letter, a miniaturized planar two-pole microwave filter with two transmission zeros is presented. The building block of this filter is a high-Q double spiral slot resonator backed by a conductor plane. The provision of a float back conductor plane allows vertical integration of this filter with other passive and active RF electronic components usually found in miniaturized wireless transceivers. The conductor plane also provides a coupling mechanism between the input and output of the filter giving rise to transmission zeros. It is shown that the location of transmission zeros can easily be adjusted and significant out-of-band rejection be achieved using only two miniaturized double-spiral resonators. The design procedure and fabrication of a two-pole filter operating at 2.11GHz is demonstrated and a very good agreement between measured and simulated results is shown