UWB harmonic-suppressed miniaturized ring bandpass filter using artificial transmission lines.

This letter presents a whole UWB band suppressed ring resonator bandpass filter with small LUCs (Lowpass filter unit cells) [Lee W-K, Hwang H-Y. J Electromagn Eng Sci. 2014;14:387-392.] based on artificial transmission lines [Martin F. Artificial Transmission Lines for RF and Microwave Applications. 1st ed. New York: Wiley; 2015]. Two LUCs are used as building blocks for miniaturization and harmonic suppression of the ring resonator of the filter. Design equations for proper characteristic impedances of the ring and for proper stopband transmission zeros of the LUCs are newly presented. Fabricated filter shows insertion loss of 2.3 dB at center frequency of 2.55 GHz, fractional bandwidth of 2.5%, and good harmonic suppression about 20 dB in whole ultra-wide band, which agreed well with the simulation results. The ring area of the proposed bandpass filter has 36% of that of the conventional one. [ABSTRACT FROM AUTHOR]