Rectenna with a High Quality-Factor Short-Circuited Transmission Line

This paper presents the criteria for designing a high quality-factor (Q) inductor based on a short-circuited transmission line (SCTL). The SCTL is used in the matching network of a rectenna to increase its power efficiency. The proposed rectenna operates at 868 MHz and consists of an L-matching network and a half-wave rectifier. An analytical study shows that Q increases for substrates with higher thickness, lower relative permittivity and lower loss tangent. Moreover, it reaches a maximum for an optimum width and length of the SCTL. Some of the theoretical results were checked with simulations. Simulations of the rectenna were performed using a Rogers 5880 substrate with thicknesses (d) of 1.57 mm and 3.175 mm. The simulated rectennas were fabricated and tested for input powers of -10 dBm, -20 dBm and -30 dBm, achieving efficiencies of 57.7%, 36.7%, and 12.1% for d = 1.575 mm, and of 57.1 %, 37.5 % and 13.0 % for d = 3.15 mm, respectively. Efficiencies rank among the highest reported in literature.