Energy harvesting technologies are required for autonomous applications, like sensors, for which a long-time power sourcing from a battery is infeasible. An energy harvester converts different forms of environmental energy into electricity. It can replace, totally or partially, the batteries of certain micro-systems that have low-energy requirements. Therefore, the authors exploit the use of electromagnetic waves from broadcasters to power wireless sensors. The authors propose to realize harvesting operation at typical ambient radio frequency power levels found within urban environments. To explore the potential for ambient RF energy harvesting, an RF spectral survey was undertaken from outside in Paris. The average RF power in the frequency range 0.9-3 GHz is about −12 dBm. The harvester includes an antenna, an impedance-matching network, and a rectifier; it was designed to cover two frequency bands from the largest RF contributors (GSM1800 and UMTS Band 1). A prototype is designed, fabricated, and measured. The RF-to-DC rectifier and the choice of the load to optimize the amount of DC power are presented. An efficiency of ∼45% was observed experimentally for the UMTS Band 1 and 33% for the GSM1800, whenever the incident power is −7 dBm. Numerical and experimental data are reported and discussed