In recent years, it is one of the biggest disadvantages of wireless sensors have vital importance that they are supplied by batteries. It is possible to overcome this deficiency by RF energy harvesting systems. In this work, the system generating electrical energy efficiently from two different RF signals have different frequencies is presented. Compared with conventional single frequency RF energy harvester, with the proposed dual band RF energy harvester, an increase is achieved 39% and 78% for 575 MHz and 900 MHz input frequencies at 0 dBm signal level, respectively. In a wide range of frequencies in the range of 400 MHz to 1000 MHz, the efficiency is obtained over 50% from the proposed system. Thus, the system can be used efficiently in an environment including any one or more DTV and GSM signal. The proposed circuit can be used effectively on the RF signals have the level of more than -15 and -10 dBm.