This paper presents a novel radio frequency (RF) energy harvester (EH) with improved RF-to-DC conversion efficiency towards implementing fully integrated single-chip in 130nm CMOS technology. The proposed energy harvester can drive low power wireless sensors, biomedical sensors and Internet of Things (IoT) devices without the need for any external DC supply. Utilizing -11.8 dBm (66μW) scattered RF signal from ambient, the proposed EH can generate 0.966V across 70KΩ load resistor with an RF-to-DC conversion efficiency of 20.198% at 900MHz. Similarly, for 1800MHz, results are 1.022V and 22.59% respectively. Moreover, simulated load currents for 900MHz and 1800MHz are 13.8 μA and 14.59 μA correspondingly. As a possible solution to achieve more power, the multiband energy harvesting approach is also proposed. The simulated output DC voltage is 1.406V with 21.39% conversion efficiency by combining both 900MHz and 1800MHz RF signals.