An NLTL-Based Harmonic Backscatter System for 6-DoF Sensing

This paper presents a real-time sensing system for full 6 degree-of-freedom (6-DoF) recognition based on a harmonic backscatter (HBS) tag with a nonlinear transmission line (NLTL) passive harmonic converter. The proposed approach is applicable to motion capture and human-machine interaction in healthcare and rehabilitation scenarios, providing a practical and low-power radio frequency (RF) perception framework with integrated posture recognition capability. An analytical model of the RF link’s harmonic generation is developed, and both theoretical and experimental results validate the millimeter-level ranging accuracy via HP-SFCW processing and enhanced 6-DoF posture sensing capabilities. Implemented on an FPGA-based in-sensor computing architecture, the system achieves real-time posture perception at 15 Hz within an indoor environment