Design of Compact Tri-band Bandpass Filter Based on Stub-Loaded Resonators

A compact tri-band bandpass filter with controllable passband and low loss is proposed. The filter is composed of resonators A and B. Resonator A is a quad-mode stub-loaded resonator(SLR) that controls the second and third passbands; The resonator B is a dual-mode stub-loaded resonator that controls the first passband; Finally, a tri-band bandpass filter with a size of
$\mathbf{15}.\mathbf{90}\mathbf{mm}\times \mathbf{18}.\mathbf{42}\mathbf{mm}(\mathbf{0}.\mathbf{13}\boldsymbol{\lambda}_{\mathbf{g}}\times \mathbf{0}.\mathbf{15}\boldsymbol{\lambda}_{\mathbf{g}})$
is designed.