Compact dual-mode interdigital-loop resonator and filter application

A novel compact dual-mode resonator is proposed. This proposed dual-mode resonator was composed of the following features: the series capacitance is inserted for miniaturization and it´s effect was also analyzed, and open stub was applied on symmetric plan for dual-mode behavior. Using this dual-mode resonator, dual-band bandpass filter of 0.2 λ_g by 0.28 λ_g (at odd mode resonance) for WLAN application was designed and fabricated providing an excellent verification on the attractive features of the filter, such as compact size and extra transmission zeros without increase order of filter.