Folded quarter-wave resonator filters with Chebyshev, flat group delay, or quasi-elliptical function response

This paper presents the design and realization of a new class of miniaturized microstrip filters using folded quarter-wave resonators. Various kinds of filter response are realized by proper arrangement of the resonator. The design rules for cross-coupled filters with quasi-elliptical function and flat group delay response are provided. The measured results match theoretical predictions well.