We can use radio frequency energy in order to fuel autonomous sensors. This energy can be which is radiated into the environment or directly from a source dedicated to it. For this we will use antennas which will receive low signal powers, in this case 0 and -10 dBm with 868MHz of frequency, that through an adaptation network, (formed by a capacitor and a coil), and a rectifier-filter signal (using diode HSMS2850 and a capacitor of 1nF) will make that power transference delivered to the sensor it will be the maximum possible. We decided that the antenna resistance (R_s) was 50Ω (a typical antenna value) because at the moment to measure real results we will use a signal generator with a 50Ω output. This project is based on impedances adaptation of LC network to obtain high efficiencies of the circuit. In simulation section with ADS-2006 program we obtained efficiencies around 70% where the circuit was fuel at 0dbm. Meanwhile the circuit was fuel at -10 dbm the efficiency didn't overcome the 60%. In this case the components were a 0.6pF capacitor and a 31.3nH coil. In implementation of PCB section with an input power of 0 dBm (with a 0.6pF capacitor and a 33nH coil) the circuit overcame the 50% and with -10dBm it overcame a performance upper than 40%, but all this with an unwanted frequency.