Near-Field Focusing mmWave Leaky Wave Antenna for Enhanced Wireless Power Transfer

A near-field focusing millimeter-wave (mmWave) leaky wave antenna (LWA) using non-periodic rectangular slots for wireless power transfer application is presented in this paper. The proposed design is based on a rectangular substrate integrated waveguide and fed by two coaxial probes. The phase distribution in the near field and slot positioning are derived by a theoretical approach. By skillfully manipulating the slot positions, the uniform slot elements facilitate an in-phase superposition within the desired near-field region, resulting in a significant focusing effect. To explore the performance of the antenna, the focusing effect is examined at a 2D focal distance of (10$\lambda$, 10$\lambda$). Here, $\lambda$ represents the free space wavelength at 28 GHz. While maintaining a beam steering from 27.5 GHz to 30.5 GHz, an impressive 69% enhancement compared to the traditional far-field LWAs is obtained at 28 GHz. This breakthrough design not only offers a substantial enhancement in focusing capability but also opens the door to an emerging transmitting system with a notably high beam efficiency for wireless power transfer (WPT).