A new multiband circular polarized rectenna is implemented as a radio frequency (RF) power harvesting system tuned for the quad bands of 1.8 GHz (GSM 1800), 2.4/5.8 GHz (WLAN), and 3.6 GHz (WiMAX). An innovative monopole antenna is made for the rectenna; consisting of an octagonal shaped microstrip patch, loaded with an I-shaped rectangular slot and three L-shaped stubs so that the antenna creates circular polarization at the quad bands. The second part of the rectenna is a multi-frequency impedance matching network (IMN) set between the antenna and the rectifier circuit. The IMN includes some parallel shunt stepped impedance stubs (SIS), which provides eight-band matching network and connected to the rectifier, functioning at the frequencies of 0.84, 1.29, 1.68, 3.08, 3.45, 4.31, 5.11, and 5.49 GHz. Simulation and experimental results verify that the system operates well and deliver proper DC power. For input power of 0 dBm, the peak RF-to-DC power conversion efficiencies are 62.69%, 63.28%, 46.94%, 30.23%, 45.69%, 16.42%, 8.13%, and 19.61% at the eight frequency bands, which is higher than the recently reported rectennas.