Design of Cross-Coupled Duplexers Based on Substrate Integrated Waveguide Hexagonal Resonators.

Area of Science:

• Electromagnetic Engineering
• Microwave Engineering
• Materials Science

Background:

• Traditional waveguides face integration challenges, while microstrip lines suffer from high-frequency radiation loss.
• Substrate Integrated Waveguide (SIW) technology offers a solution by combining waveguide properties with planar fabrication.
• Hexagonal resonators in SIW provide a unique geometry for improved performance characteristics.

Purpose of the Study:

• To propose a novel bandpass duplexer design overcoming limitations of existing technologies.
• To leverage SIW hexagonal resonators for enhanced integration and reduced signal loss.
• To achieve high performance in terms of isolation and out-of-band rejection for duplexer applications.

Main Methods:

• Design of a bandpass duplexer utilizing substrate integrated waveguide (SIW) hexagonal resonators.
• Integration of rectangular resonator flexibility with circular cavity quality factor.
• Implementation of a three-cell cascaded structure with cross-coupling theory to introduce transmission zeros.
• Fabrication and measurement of a duplexer prototype operating at 6.8 and 7.9 GHz.

Main Results:

• The fabricated duplexer demonstrated excellent isolation between passbands (-55 and -43 dB).
• Out-of-band rejection exceeded -40 dB, indicating effective signal filtering.
• Measured results closely matched simulation predictions, validating the design approach.
• The design achieved relative bandwidths of 3.5% and 7.5% for the respective center frequencies.

Conclusions:

• The proposed SIW hexagonal resonator duplexer effectively addresses the trade-off between integration and radiation loss.
• This design offers low radiation loss, high power handling, and planar integration advantages.
• The developed scheme presents a promising new approach for high-performance duplexer design in microwave and millimeter-wave frequencies.