Abstract
A new balun bandpass filter (BPF) designed in the form of the substrate integrated waveguide is proposed in this article. To achieve 180° phase difference, two balanced output ports are placed on both sides of the substrate, respectively. To realize the BPF performance with high-frequency selectivity, a two-pole filter with the source and load coupling is introduced. A prototype was fabricated and measured. Both simulated and experimental results are provided with good agreements. The measured results indicate that the proposed balun BPF has nice balance performance with less than 0.2 dB amplitude imbalance and better than 3.5° phase imbalance, along with compact size and high selectivity.
Disclosure statement
No potential conflict of interest was reported by the authors.