A Hybrid CMOS-Polyimide Adaptive Force Radiometric Array With 3–5-GHz Wireless Connectivity

To bridge the gap between force sensing technologies and wireless communication systems, this letter introduces a hybrid force radiometric array with direct analog force-to-radio-frequency (RF) radiation conversion. The design comprises a thin-film force sensor array, a flexible printed circuit board, an array of four class-D low-power voltage-controlled oscillators (VCOs) in 65-nm CMOS technology for voltage-to-frequency conversion, and a broadband multiport loop antenna for RF radiation. Class-D VCOs consume less than 2 mW of dc power and the system presents a linear force-to-frequency relationship. The measured radiometric array can achieve a force dynamic range of 105 N, a resolution of 0.1 N, and confirmed wireless connectivity of more than 5 m (limited by the laboratory dimensions).