Abstract-Various rectenna designs have been investigated to deal with a big growth interest in wireless energy harvesting. This paper presents a rectenna design of dual frequencies operating antenna at microwave bands which are 1.9 GHz and 2.45 GHz. Tunable impedance matching is considered necessary to supply maximum power transfer from low energy source. Since power efficiency is such a main concern, the perfect matches are desired. The front-end of dual-band receiving antennas convert microwave input signal into alternating current (AC) form. The matching network and the load impedances of the rectenna design are in matched condition to decrease reflected power and to increase input power to rectifier. Then, the power is rectified by the CMOS rectifier to generate direct current (DC) voltage that required for the electronic load. Finally, the system performance is verified with PSpice simulation results. In dual frequency operation, with -20 dBm power source over 1M Ω resistance load, the harvester system is able to generate DC output voltage of 2.09 V and the efficiency reaches 43.68% which is indicate high efficiency for a lower power input level application. The stated results represent that a dual-band rectenna of the energy harvester system could produce 1.62% to 10.18% more efficiency over a single-band rectenna at 1.9 GHz and 2.45 GHz respectively. Index Terms-Dual-band antenna, rectifying, radio frequency, energy harvester, MOSFET, microwave band.