Design of a Compact Balanced Bandpass Filter based on CSRR-loaded Substrate Integrated Waveguide Structure

摘要

A compact balanced bandpass filter (BPF) based on complementary split ring resonator (CSRR) -loaded substrate integrated waveguide (SIW) structure is reported in this paper. Both TE102 and T-201 modes of the SIW cavity can be excited under differential-mode (DM) operation with the proper positions of the balanced feeds. Meanwhile, the CSRR etched on the top layer of the substrate can also be excited by the axial electric excitation. Then, three transmission poles and two transmission zeros (TZs) have been obtained which improve the selectivity of the DM passband. To verify the above design concept, an X-band prototype operating at 8 GHz has been fabricated and measured. A good agreement is observed between the simulations and the measurements.