In this paper an energy harvester at 35GHz has been developed which known as rectenna. An array of rectangular microstrip patch antenna with 16 elements was used to efficiently convert RF to DC signal. A step impedance low pass filter is used between antenna and rectifier circuit to suppress second order harmonic generated by diode. A GaAs Schottky diode MA4E1317 was used in parallel with load as half wave rectifier circuit. The fabrication process is based on conventional optical photolithography to obtain an integrated circuit. The maximum RF to DC conversion efficiency of 67% was successfully achieved with input RF power of 7mW at 35.7GHz.