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This paper introduces a novel design methodology for a dual-band branch-line coupler (DBBLC) that, for the first time, facilitates practically unlimited band ratio, enhanced flexibility in power division, and arbitrary port termination impedance concurrently. This approach ensures precise power distribution, matching, and isolation requirements by utilizing a generalized coupler core paired with an L-section impedance-matching network. This paper details an innovative and comprehensive analytical strategy for DBBLC design, which overcomes the limitations noted in prior research by deriving a generalized formula for the power division ratio (k) and simplifying the design equations to decrease complexity. This method enables the simultaneous realization of varied power division ratios, frequency ratios (r), and port impedances ( Zp ), thus offering remarkable design versatility. The effectiveness of this new analytical design methodology is corroborated through several design examples. Moreover, two prototype models operating at 1 GHz/2.5 GHz ( r=2.5,k=0 dB) and 1 GHz/2 GHz ( r=2,k=4.77 dB) frequencies, constructed on Rogers’ RO4003C substrate, exhibit >22 dB return loss, <0.64 dB amplitude imbalance as well as <1° phase imbalance of the transmission parameters and >25 dB isolation at all the targeted frequencies. Therefore, the development and validation of this new DBBLC structure, as demonstrated by the strong correlation between our simulated and experimental findings, not only surpasses the capabilities of existing models, but also broadens the applicability of dual-band couplers in modern wireless communication systems.
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This content will become publicly available on January 1, 2026
On the Design of a High Band-Ratio Mid-Section Crossed Dual-Band Branch-Line Coupler With Arbitrary Power Division Ratio Using Perturbation Factor
This article presents a Mid-section crossed dual-band Branch-Line Coupler (MBLC) with port extensions, along with a new design methodology for both complex and conventional structured branch-Line couplers. The proposed MBLC structure features a conventional branch-line coupler with a crossed line at the center, as well as an L-section impedance matching network at all four ports, which facilitates analysis and design. A comprehensive theoretical analysis is performed to derive closed-form design equations for determining the design parameters of the coupler using a perturbation factor. The analysis demonstrates that the proposed MBLC can support a wide band ratio of up to 11, indicating a broad operating frequency range. To evaluate the performance of the proposed MBLC, two prototypes were fabricated on a 62 mil Rogers 4003C substrate, operating at 1 GHz and 2 GHz for equal and unequal power division cases. The simulated and measured results for both prototypes showed an excellent match, with a magnitude imbalance of less than 4% and a phase imbalance of less than 2%. Overall, the proposed MBLC with port extensions in conjunction with the new design methodology demonstrated promising results for the development of efficient and effective dual-band branch-line couplers
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- Award ID(s):
- 2104513
- PAR ID:
- 10639954
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- IEEE Access
- Volume:
- 13
- ISSN:
- 2169-3536
- Page Range / eLocation ID:
- 4609 to 4620
- Subject(s) / Keyword(s):
- Branch-line coupler, dual-band, impedance matching, microwave circuits, power divide
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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