In this paper, a methodology to design non-50 Omega antennas for energy harvesting is presented. Two prototypes are simulated and realized on an epoxy substrate: one operating at 433 MHz and 900MHz, the other at 900MHz and 2.4GHz. These antennas are designed to match the input impedances of an integrated radio-frequency harvester for an output voltage of 1V, value chosen considering the voltage needed to power the new generation of micro-controllers and electronic circuits for the Internet of Things. The measurement results indicate a reflection coefficient below -10 dB at the frequencies of interest, validating the methodology.