Design of microstrip tri-mode balun bandpass filter with high selectivity

作者：Lin Shanming; Wang Jianpeng^*; Zhang Gang; Hong Jiasheng

来源：Electronics Letters, 2015, 51(13): 998-999.

DOI：10.1049/el.2015.1047

• microstrip filters
• baluns
• band-pass filters
• microwave resonators
• coupled circuits
• coplanar waveguides
• microstrip transitions
• strip lines
• microstrip trimode balun bandpass filter
• balun BPF
• filter-type function
• balun-type function
• multimode stepped-impedance resonator
• SIR
• parallel coupling
• phase difference
• transition structure
• coplanar waveguide
• microstrip-CPW-microstrip transition
• microstrip-CPS-microstrip transition
• coplanar stripline
• balanced output port design

A new microstrip tri-mode balun bandpass filter (BPF) with good filter-type and balun-type functions is presented. To realise the tri-mode BPF performance, the multimode stepped-impedance resonator is introduced and parallel coupled to both the balanced and the unbalanced ports. To achieve 180 degrees phase difference, two types of transition structures, i.e. the microstrip-coplanar waveguide-microstrip transition and the microstrip-coplanar stripline-microstrip transition, are adopted for the two balanced output ports design, respectively. A balun BPF operating at 2.6 GHz is designed and fabricated to validate the feasibility of the new approach. Results indicate that the proposed balun BPF exhibits not only high selectivity with two transmission zeros locating at 1.7 and 3.7 GHz but also good balance performance with 0.5 dB magnitude imbalance and 5 degrees phase imbalance between the balanced outputs.

• 出版日期2015-6-25
• 单位南京理工大学