Mobile phones have become the most popular and the fastest means of communication as a result of the substantial reduction in their prices in recent years. However, these mobile phones use rechargeable battery which requires recharging, this is challenging because of the insufficient electricity supply and alternatives. In Uganda, only 28% of the population is currently having access to electricity and less than 7% of the rural population has electricity service. Telecommunication companies have provided network coverage to almost the entire country with GSM 2G coverage at 93%. The mobile phone users in the rural areas are however few because of inadequate electricity and burden of long distance travelling to town centers in order to charge the phone batteries. This study opts for a power source alternative based on using microwave harvesting. The approach is to convert the microwave signal of 900MHz frequency band from the existing telecommunication downlink frequency into DC voltage. The design is based on the spiral antenna for receiving the 900MHz frequency band. The design is divided into two main parts, namely antenna and charge pump voltage doubler. The spiral antenna is used to harvest and convert the microwave signals into electrical signals; the charge pump helps to convert the low AC to DC voltage capable of charging the battery. The simulation design is tested with Multisim simulation software and the results revealed 5V of DC power generated by means of seven stages voltage doubler. Thus, an alternative source of power for mobile phone battery charging.