In this work, a high-efficiency radio-frequency energy-harvesting system that takes use of the Portuguese Digital Television signal (750–758 MHz) to obtain DC power is proposed. To be useful, it is optimized to operate at low-power conditions. For the rectifier, three different solutions are presented: a single-series diode, a single-shunt diode, and a voltage-doubler configuration. The efficiency is similar for the three rectifiers – about 54% with a sine-wave excitation and −10.5 dBm of input power. Field measurements with the voltage-doubler have shown 63% efficiency for the same input power.