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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. 

Electrochemical sensors have become a pivotal tool in ensuring the safety and security of the global food supply chain, which is crucial for public health, economic stability, and environmental sustainability. Modern food systems, with their complex global distribution and varied processing methods, require advanced solutions for detecting contaminants and maintaining food quality. This review delves into recent advancements in electrochemical food sensor technology, highlighting their operating principles, types, cutting-edge materials, and methods enhancing their effectiveness. These sensors are adept at identifying a broad range of foodborne pathogens, chemical contaminants, and adulterants while monitoring food freshness and quality. Innovations include using nanomaterials and conductive polymers and shifting towards miniaturized, portable devices for on-site and real-time analysis. The review also addresses challenges such as sensitivity, selectivity, and matrix effects, pointing out emerging trends and future research avenues to overcome these hurdles. Regulatory and standardization issues relevant to adopting these technologies in food safety protocols are also considered. Highlighting the last three years, this review emphasizes the indispensable role of electrochemical sensors in boosting food safety and security and the need for ongoing innovation and cross-disciplinary cooperation to advance this area. 

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