RF/Microwave Filters with Beyond-Transmission-Band Flat Group Delay for Advanced Digital Communications

RF/microwave filter design typically prioritizes high selectivity, sharp rejection, and flat in-band amplitude response. However, these features often cause large group-delay variations, which can severely affect applications like digital communications by introducing inter-symbol interference. This talk presents recent advances in developing filters that maintain quasi-flat group-delay responses beyond the 3dB transmission band while also incorporating transmission zeros in out-of-band regions. Such designs improve signal integrity without sacrificing selectivity. Experimental validation through proof-of-concept prototypes demonstrates the practical feasibility and effectiveness of these innovations, highlighting their potential for advanced communication systems requiring both stringent filtering performance and minimal group-delay distortion.