In this work the operation of a MOSFET based rectifier, composed of multiple stages of voltage doubler circuits used for radio frequency (RF) energy harvesting, is investigated. Analytical modeling of the input stage of the rectifier consisting of short-channel diode-connected transistors is carried out, and the equivalent input resistance obtained is used along with simulation results to improve impedance matching in the harvester. The criteria for voltage boosting and impedance matching, that are essential in the operation of energy harvester under low ambient RF levels, as well as the design considerations for a pi-match network to achieve matching to 50 Ohms, are elaborated on. In addition their application is demonstrated through simulations carried out using Advanced Design System (ADS) simulator. Furthermore, measurement results of an already fabricated dual-band RF harvester are presented, and the approach taken to improve the antenna design from the harvester chip measured input impedance is discussed. The integrated antenna-harvester system tested was capable of harvesting ambient RF power and generating DC output voltage levels above 1 V.