Compact LTCC-Integrated Fully Decoupled Biasing for Wireless Sensors

This paper presents the design, simulation, fabrication, and measurement of a compact bias-tee fully embedded in an LTCC substrate suitable for wireless sensor applications. The structure features two parallel-plate capacitors, one at each RF port, and a centrally placed inductor for DC injection, providing complete DC isolation while maintaining RF continuity. Unlike conventional bias-tees, this configuration isolates both RF ports from DC bias, making it ideal for sensitive RF front-ends and embedded sensor systems. Simulated and measured S-parameters confirm excellent RF performance with low insertion loss and high isolation. The device was fabricated using DuPont 951 LTCC, and its internal structure was validated using X-ray imaging. This embedded bias-tee enables reliable, compact integration in multi-functional sensor systems, supporting co-packaged RF components and minimizing interference in high-density multi-layered devices and circuits.