This article presents a high-efficiency dual-band rectenna, for RF energy harvesting in GSM bands (900-1800 MHz).The rectifier used is a dual-diode rectifier topology based on a Delon voltage doubler. To ensure, the highest efficiency as possible, source-pull simulations are used to determine the optimal diodes input impedance. The antenna is a spiral planar structure, where two slots ring resonators have been added to expand bandwidth at low frequencies without increasing its initial size. It is associated with a broadband balun to transform its impedance into the desired 50-Ω rectifier input impedance. The antenna and balun are sized for broadband operation to cover the main wireless communication bands. Measurement results show high RF-DC conversion efficiencies of 28% and 20% at 890 MHz and 1780 MHz, respectively,for a low RF input power of −20 dBm and with a 10 kΩ DC load. Efficiency reaches 43.5% with a dual-tone signal at −20 dBm.