Enhancing Long-Range Battery-Free Communication: A Passive Lens-Enabled Broadbeam Harmonic mmID for Emerging IoT Systems

For the first time, the authors propose a novel 3D lens-enabled, fully-passive harmonic retrodirective mmID with wide spherical angular coverage and ultra-long-range capabilities. The mmID features a bi-convex dielectric lens for high gain and solid angular coverage, paired with an RF front-end comprised of 25 capacitive-coupled dual-polarized ‘pixel’ antennas and a fully-passive frequency-doubling circuit. The proposed system achieves a solid angle coverage of 2.68 sr and a peak RCS of -31.9 dBsm, representing the highest detectability across solid angles among harmonic RFIDs. The mmID was tested up to 150m at incident angles of 0° and 55°, to demonstrate its ultra-long range capabilities even at highly oblique angles. With 5G/mm-Wave EIRP of 75 dBm, the mmID is projected to reach ranges of 2.7km at boresight and 1.6km at 55°. With its fully-passive design and high detectability, this mmID offers a transformative solution for next-generation ultra-long-range 5G/mmWave IoT applications.