This paper presents a study of Schottky diode rectenna (rectifying antenna) for RF energyharvesting systems. These rectennas are suitable for wireless sensors with the rechargeablebattery technology especially at low power densities. A rectifying circuit is proposed withsingle high responsivity Schottky diode for RF-DC conversion. A matching circuit is optimisedto improve not only the power transfer between the antenna and the diode but also to rejectharmonic signals. The radiating part is a monopole antenna, with a large bandwidth in thefrequency domain and an omni-directional radiation pattern in the azimuthal plane. We showthat antenna frequency response takes part in the improvement of the efficiency. The rectifieris integrated with the antenna on a printed circuit board, leading to 30% of size reduction withthe same performance. The aim is to reach the highest efficiency with a single tone signal anda compact rectenna. This rectenna was simulated using both Agilent ADS and Ansoft HFSSsoftware. An output DC voltage of 210 mV was measured inside an anechoic chamber with areceived a single tone signal of 2 μW/cm2power density. The highest efficiency of 34 % wasobtained at a power density of 1.3 μW/cm2.