• Proposes a novel isomeric resonator configuration combining two ridge waveguide resonators and a half-wavelength resonant slot within a single cavity.
• Embedding a tuning post in the ridge reduces the TE101 mode frequency by up to 45% without affecting the TE102 harmonic, enabling simultaneous miniaturization and wide stopband.
• The HWRS introduces adjustable cross-coupling, allowing independent control of a transmission zero in the upper stopband via slot thickness.
• Measured prototype achieves ~90% size reduction and superior upper stopband rejection relative to traditional ridge waveguide filters.