An ultracompact CRLH-TL bandpass filter for VHF applications

Abstract

This article proposes a new design approach to an ultracompact composite right-/left-handed transmission line (CRLH-TL) bandpass filter with good passband and very broad stopband performances. In order to reduce the size, a series connection of the interdigital capacitor and shorted spiral inductor for realizing CRLH-TL is adopted and optimized to create the target Terrestrial-Digital Multimedia Broadcasting (T-DMB, 174-216 MHz) bandpass filtering. T-DMB was developed in South Korea. The results of a Bloch impedance analysis suggest that the proposed approach generates good impedance matching. The proposed filter has overall dimensions of (g)/19 by (g)/34 in terms of a center frequency of 180 MHz, a 3 dB fractional bandwidth of over 28%, an insertion loss of much lower than 2 dB, and a good return loss performance in the predicted and measured results.