Synthesis method for the parallel-coupled stub-loaded resonator filters

This paper describes a synthesis method for parallel-coupled filters based on short-circuited stub-loaded resonators. Synthesis formulas were derived for homogeneous medium. Simulations are presented to validate the theory for three relative bandwidths 2, 4 and 8 %. For a proof-of-concept a third-order stripline bandpass filter was designed with a passband ripple of 0.01 dB and a relative bandwidth of 4.5%. Theory, simulations and measurements are in good agreement and thus validate the theory.