Three Folded U -Shaped Resonators with Good Harmonics Suppression for S-Band Radar Applications

A miniature bandpass hairpin filter using planar technology was described in this paper. It consists of three resonators folded in a U-shape and coupled with each other. The resonators have the same size $(40\ \times 2.3\times 0.035)$ mm 3, and they are printed on an RT/duroid-5880 dielectric substrate having a permittivity $\epsilon_{r}=2.2$, a loss tangent $\tan(\delta)$ equal to 0.0009, and a height h of 1.524 mm. A rectangular slot was etched on the ground plane under the substrate to optimize the results which were simulated using the Ansys HFSS (High-Frequency Structure Simulator) software. The obtained results showed that the filter performed well in terms of reflection coefficient $S_{11}$, Voltage Standing Wave Ratio (VSWR), and insertion losses $S_{21}$, which encouraged us to recommend it for S-band (2- 4GHz) applications used for air traffic control by airport surveillance radar, some satellites for communication, and meteorological radar, particularly, those used by NASA (National Aeronautics and Space Administration) to communicate with the ISS (International Space Station) and the (SC) Space Capsule.