Design of folded half wave resonator

This paper presents the design of compact hairpin resonator operating at S-band. The chosen frequency is 2.45 GHz, suitable for wireless local area network (LAN) application. The resonator structure consists of internally coupled-line. Design parameters that affect the operating frequency and the first spurious frequency were investigated. The determination of impedance and length ratios are important prior to the design in order to achieve minimum resonator size. Investigations were performed to study resonator´s behavior for various sizes of internal coupled-line gap and length to the operating frequency. Bigger gap size and shorter coupled-line length caused the resonator to operate at a frequency higher than expected.