Compact Balanced Bandpass Filter Based on Equilateral Triangular Patch Resonator

Abstract

In this brief, a new balanced bandpass filter based on equilateral triangular patch resonator (ETPR) is presented. By introducing rectangular slot in the middle of the ETPR, TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode can be controlled for miniaturization of design and separated away from disturbed mode near the passband for decent performance. Furtherly, based on the developed coupling topology, six adjacent slotted ETPRs are elaborately arranged to construct a fourth-order balanced BPF with a good differential-mode (DM) passband, sharp frequency selectivity, as well as high common-mode suppression (CM). To validate the design concept and method, a balanced BPF operating at 5.7 GHz with a 3-dB fractional bandwidth of 12% is designed and fabricated. Good agreement between simulated and measured results validates the proposed design concept.