Dual-Band Compact Rectenna for UHF and ISM Wireless Power Transfer Systems.

A dual-band UHF/industrial, scientific and medical (ISM) compact rectenna with wideband UHF matching (855–935 MHz) covering all, EU, U.S., and Chinese UHF radio frequency identification (RFID), standards is presented. The proposed design consists of a compact single-port, dual-band antenna, a three-port dual-branch matching network, and two voltage doubler rectifiers implemented with Schottky diodes and terminated with a common 10 kΩ load. For each band, the measured RF-to-dc efficiency is around 60% for a −5 dBm unmodulated signal. The wideband behavior of the rectenna supports harvesting of multitone signals. The use of a six-tone signal increases the maximum RF-to-dc efficiency of the dual-band rectifier, from approximately 60% for a single-tone UHF signal (890 MHz) to 80% for a six-tone signal for a received RF power of −5 dBm in both cases. A signal generator is used to generate a six-tone signal of equally weighted and equally spaced (10 MHz separation) monochromatic tones, with a total bandwidth of 50 MHz. The measurement results demonstrate that the dc voltages rectified from the two separate RF signals are effectively superimposed on the load, providing a clear advantage compared to single-band rectennas. The single-layer, compact design with a size of 80 × 45 mm2, with a high RF-to-dc efficiency, is an excellent candidate for wirelessly powered RFID tags. [ABSTRACT FROM AUTHOR]