Ultra-Wideband Bandpass Filter Based on Composite Right/Left Handed Transmission-Line Unit-Cell

This paper presents a novel high performance ultra-wideband (UWB) bandpass filter that satisfies FCC UWB specifications. The filter is based on a composite right/left handed (CRLH) structure consisting of an asymmetric unit-cell with a short circuited inductive stub that exhibits stopband rejection level greater than 25 dB at both the lower and upper band edges while maintaining an insertion-loss of less than 0.5 dB across its passband. In addition, a simple and effective technique is proposed to create and control sharp rejection notch-bands within the filter's passband in order to provide interference immunity from undesired radio signals, such as wireless local area networks (WLAN) that co-exist within the UWB spectrum. The proposed technique was verified practically to validate the design methodology. The experimental results of the prototype circuit are presented and compared with the simulation results. The dimensions of the proposed filter are 0.37λ × 0.10λ (i.e., 16.4 × 4.8 mm²). The filter's characteristics and compact size make it suitable for UWB systems.