Dual-Band Branch-Line Coupler Based on Crossed Lines for Arbitrary Power-Split Ratios

Area of Science:

• Electrical Engineering
• Microwave Engineering
• Electromagnetics

Background:

• Branch-line couplers are fundamental passive microwave components used for signal splitting.
• Existing dual-band couplers often lack flexibility in independently controlling power-split ratios for each band.
• Achieving wide variations in power division across different frequency bands presents a significant design challenge.

Purpose of the Study:

• To present a novel design for dual-band branch-line couplers.
• To enable independent and arbitrary power-split ratios for two distinct frequency bands.
• To enhance stopband performance using integrated open stubs.

Main Methods:

• Utilizing crossed lines at the center to facilitate independent power division for each band.
• Incorporating open stubs to improve the rejection levels in the stopband.
• Developing a complete design procedure with illustrative design curves.
• Fabricating and experimentally validating three dual-band coupler prototypes.

Main Results:

• Demonstrated dual-band branch-line couplers with independent power-split ratios for each band.
• Achieved significant power-split ratio differences, including a record -13.3 dB variation between bands.
• Experimental results show excellent agreement with theoretical and simulated designs.
• Validated designs at 1 GHz and 2.5 GHz with various power-split combinations.

Conclusions:

• The proposed design effectively achieves independent and arbitrary power-splitting for dual-band branch-line couplers.
• The use of crossed lines and open stubs provides a versatile and high-performance solution.
• The demonstrated capability for large power-split differences opens new avenues for dual-band microwave circuit design.