Publication: Studies on Substrate Integrated Coaxial Line (SICL) Based Microwave & Millimeter-Wave Active Circuits
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2024-08-28
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Indian Institute of Technology, Jodhpur
Abstract
Microwave and Millimeter-Wave (mmWave) active circuits are pivotal in modern communication systems, and other emerging technologies. The research work in this thesis is focused on implementing the microwave and millimeter wave active circuits such as bias tee circuits, amplifiers, SPDT switches, oscillators, and mixers. Various circuit technologies have been available to implement active circuits for the past thirty years. Bulky air-filled waveguides and planar circuit technologies such as microstrip, GCPW, and SIW are well-established in microwave and millimeter-wave circuit design. Air-filled waveguides offer lower loss, but they are bulky, while the aforementioned planar technologies provide compact size at the expense of higher loss. In recent decades, a technology known as substrate-integrated coaxial lines (SICL) has emerged as a bridge between coaxial lines and other planar technologies. SICL has gathered considerable attention from microwave and millimeter-wave circuit designers due to its compact size, lower loss, and electromagnetic shielding capabilities. This planar form of the coaxial line structure can be fabricated using printed circuit board (PCB) technologies and can be seamlessly integrated with other planar circuits. In this work, the design of various microwave and millimeter wave active circuits based on SICL technology is presented. The study of RF and DC blocks in the SICL environment, the design of broadband SICL-based bias tee network with butterfly stubs with improved RF isolation, and the innovative approach of interconnecting pads for mounting SMD capacitors are presented. The SICL technology offers a viable solution to integrate SMD components in a low-profile PCB design approach with good insertion loss and isolation. Additionally, the detailed study of designing and implementing an amplifier using SICL technology highlights a novel low-cost PCB-based approach for the mmWave ISM band (23.35- 24.05 GHz). This design also includes the mounting pads for transistors and capacitors and introduces a novel matching network to enhance amplifier gain, demonstrating the potential of SICL technology in high-frequency applications. The study also presents a Ka-Band (27-28.5GHz) SPDT switch for duplexer applications using SICL technology. The switch incorporates an innovative RF isolation network in an asymmetric stripline environment, achieving optimal isolation and performance, as validated by an equivalent circuit model. Further, a high-performance reflection oscillator for Ku-band applications is designed using SICL technology, achieving low phase noise and high output power. Lastly, the research work introduces a compact mmWave downconverter mixer utilizing a SICL-based rat-race coupler, offering cost-effective, compact, and reliable performance with a low conversion loss. This mixer is ideal for high-performance mmWave integrated circuits in communication and radar systems. This research showcases the viability and effectiveness of SICL technology in various highfrequency applications, providing innovative, cost-efficient solutions for modern communication systems.
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Shukla, Saurabh (2019).Studies on Substrate Integrated Coaxial Line (SICL) Based Microwave & Millimeter-Wave Active Circuits (Doctor's thesis).Indian Institute of Technology, Jodhpur