Millimetre-wave balanced SIW bandpass filter with high common-mode suppression

Abstract

A balanced substrate-integrated waveguide (SIW) filter based on a virtual electric wall (VEW) is presented and studied in this Letter. By introducing VEW on the symmetry plane for replacing the metallic-via-array, conductor losses from metal sidewalls can be avoided. As proof-of-concept example, a six-pole balanced filter using asymmetric inductive windows is designed and fabricated with a measured centre frequency of 29.45 GHz, as well as fractional bandwidth of 7.2% to cover satellite ground terminal application. The measured response shows a good concordance with the simulated one, indicating that the proposed balanced filter has the advantages of high common-mode suppression and low insertion loss.