Dual-Mode Dual-Band Filter Using Steppedimpedance Resonator with Outer Tuning Plus-Sign

This article introduces a dual-band filter employing a folding structure of stepped-impedance resonator with an outer tuning plus-sign. The design integrates a meandered square loop resonator (SIR), with patches positioned at each corner of the square loop to induce a dual-mode response. Furthermore, the second frequency can be fine-tuned by adjusting the outer tuning plus-sign located outside the meandered loop. A dual-mode dual-band filter is designed with the first frequency at
$2.4\text{GHz}$
, featuring a loss of insertion of
$1.58{{\ dB}}$
. The first frequency exhibits transmission zeroes beside the upper and lower frequencies of the middle frequency, resulting in a sharp skirt. The second frequency, designed at 5.2
$\text{GHz}$
, has a loss of insertion of
$1.59{{\ dB}}$
and a return loss better than
$- 15{{\ dB}}$
. The design and analysis are validated using the IE3D simulator.