ADVANCEMENTS IN DUAL-BAND AND WIDEBAND RF CIRCUIT DESIGN: APPLICATIONS IN 5G AND ELECTROCHEMICAL SENSING ENSURING FOOD SAFETY

. Ahammad

doi:10.7273/000007309

The increasing demand for high-performance RF circuit components and advanced electrochemical sensors has driven significant innovations in wireless communication and food safety monitoring technologies. As food safety concerns grow globally due to contamination risks from pesticides, antibiotics, heavy metals, and pathogens, there is an urgent need for real-time, accurate, and scalable monitoring solutions. RF circuit components—including power dividers, branch-line couplers, and RF energy harvesting systems—play a pivotal role in enabling wirelessly monitored sensors for food safety. Traditional electrochemical sensors, while highly sensitive, are often limited by wired data transmission, power constraints, and real-time applicability. The integration of RF technology into these sensors allows for wireless, remote monitoring, and IoT-enabled data transmission, significantly enhancing the efficiency, scalability, and automation of food safety monitoring systems. This thesis systematically investigates dual-band RF branch-line couplers (BLCs), wideband RF power dividers, and electrochemical sensing technologies, following a structured approach that begins with fundamental theoretical modeling and progresses toward practical applications. This research critically examines the potential enhancements RF techniques could offer to electrochemical sensing applications. The thesis begins by deriving a generalized equation for the Diagonal Crossed Dual-Band Branch-Line Coupler (DBBLC) to establish a fundamental theoretical framework. The power division characteristics of DBBLC are formulated using a systematic approach that considers even-even, odd-odd, odd-even, and even-odd mode analysis. The generalized susceptance equations derived in this study help in accurately determining the admittance transformation necessary to achieve arbitrary power division and impedance matching. By setting S11 = 0 and S41 = 0, the study obtains relations for equivalent conductance and susceptance, denoted as Geq and Beq, and expresses the power division ratio k in terms of characteristic impedances of the BLC core transmission lines. The findings demonstrate that DBBLC designs can achieve high-frequency operation with an output phase imbalance of only 1.95°, making them highly suitable for 5G FR2 applications operating at 28 GHz and 40 GHz. . Following the derivation of the generalized equation, the thesis advances toward handling complex structures by incorporating perturbation techniques alongside the previously established framework. The perturbation methodology is employed to optimize the design of Mid-Section Crossed Dual-Band Branch-Line Couplers (MBLCs) by introducing impedance-matching networks that minimize reflection and maximize isolation across dual bands. The proposed MBLC is capable of supporting an exceptionally wide band ratio of up to 11 and is fabricated on Rogers RO4003C substrates, with measurement results showing a magnitude imbalance of less than 4. Extending the principles of power division, the thesis then explores the design and miniaturization of a three-way power divider (3PD) to increase the number of output terminals while maintaining high performance. The proposed 3PD employs an eight-transmission-line structure, achieving up to 69.75. The results validate the proposed methodology as an effective means of achieving high-isolation and low-loss signal distribution in RF communication networks. In the final stage, the research expands beyond RF circuit design to explore the applicability of these findings in electrochemical sensor systems. While a direct integration of RF and electrochemical sensing is not proposed, the study conducts a critical review of electrochemical sensors for food safety and traceability. Electrochemical sensors, leveraging nanomaterials and conductive polymers, provide portable, real-time detection of contaminants such as pesticides, antibiotics, and heavy metals. However, existing sensor technologies face challenges in power efficiency, wireless transmission, and scalability. By reviewing the existing literature, this research identifies areas where RF techniques could enhance electrochemical sensor performance, particularly through RF energy harvesting for power-efficient sensing, microwave-assisted detection to improve signal transduction, and wireless transmission for RF-based monitoring systems. The proposed RF DBBLC and three way power dividers can wirelessly excite multiple electrochemical sensors simultaneously through near field/far field loop antenna and are able to extract and monitor useful sensing information through a RF signal reader such as Vector Network Analyzer (VNA) connected with the DBBLC or Power dividers. By following a structured progression from generalized theoretical modeling to advanced circuit design, miniaturization, and practical applications, this thesis presents a comprehensive framework for the development of multi-functional RF circuits while also identifying potential optimization strategies for electrochemical sensors. The findings contribute to the advancement of RF circuit technologies and offer valuable insights into the future possibilities of RF-assisted sensing systems. Through a combination of theoretical derivation, analytical modeling, perturbation-based design methodologies, and experimental validation, this research lays the foundation for future innovations in wireless communication and food safety monitoring offering solutions that are real-time, scalable, and highly efficient. This progress is crucial for ensuring global food security, improving human health, and reducing the burden of foodborne diseases, ultimately leading to a safer and healthier future for all.

ADVANCEMENTS IN DUAL-BAND AND WIDEBAND RF CIRCUIT DESIGN: APPLICATIONS IN 5G AND ELECTROCHEMICAL SENSING ENSURING FOOD SAFETY

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