Energy harvesting (EH) circuits are expected to be key modules for future battery-constrained electronic devices such as mobile phones and wearable devices. Radio-frequency (RF) harvesting is one of the promising EH technologies, which converts RF signals into direct-current (DC) voltage. This paper proposed an efficient design for the voltage doubler subsystem for an RF-EH module using different types of Schottky diodes, namely HSMS-2822, HSMS-2850, and HSMS-286B. Greinacher voltage doubler circuits for multi-bands including 915 MHz (GSM), (2.4, and 5.2) GHz (WI-FI) bands are scrutinized. Up to 10 stages of Schottky diode voltage doubler circuits are investigated, where the performance is evaluated using Agilent ADS software. The results showed that the HSMS-286B Schottky diode reveals a better performance with GSM band sources, while HSMS-2850 is the Optimum choice for the WI-FI band.