Design of a compact planar dual-band rat-race coupler using improved microwave C-Section

ABSTRACT

This work presents a compact planar dual-band rat-race coupler (RRC) using improved microwave C-section. The difference in even- and odd-mode phase velocity is compensated by using wiggly lines in the structure. The wiggle depth is tuned to obtain a characteristic impedance of 70.7 Ohm and phase of 90° at 2.1 GHz and 5.3 GHz. The size of the proposed structure is 0.42 λ_g × 0.26 λ_g. The measured and simulated responses are in good agreement. The 1 dB bandwidth of the first and second bands is 670 MHz and 210 MHz, respectively, covering the GSM and WLAN bands. The structure is compact, simple, single layer, and cheap.

KEYWORDS:

• Dual-band rat-race coupler
• Microwave C-section
• miniaturized rat-race coupler
• phase velocity compensation
• slow-wave structure
• wiggly lines

Acknowledgments

The authors are grateful to the reviewers for their precious and productive comments, which have been utilized to improve the quality of the manuscript. The authors also acknowledge Mr. Pratik Mondal (PhD scholar of IIEST Shibpur) for extending his help in the completion of the project.