Capacitive-coupled resonator-based bandpass filter with controllable multiple transmission zeros at stopband

Abstract

This letter proposes novel design for a compact LTCC bandpass filter with high rejection over a wide stopband operating in the 3.4-3.6-GHz worldwide interoperability for microwave access band. The presented bandpass filter has feedback paths for the grounding inductor and the coupled capacitor to provide controllable multiple transmission zeros at 2.4/5-GHz wireless local area network band, which enhances the desired stopband rejection. The presented design derives simple formulas for synthesizing a bandpass filter to meet the specification requirement in the passband insertion loss and passband return loss as well as the stopband attenuation. The bandpass filter is designed and implemented using LTCC process and has an area of 2.0 × 1.25 mm 2. Experiments results are very agreement with the full-wave simulation results. © 2013 Wiley Periodicals, Inc.