This paper presents a study of Schottky diode rectenna (rectifying antenna) for radiofrequency (RF) energy-harvesting systems. These rectennas are suitable for wireless sensors with the rechargeable battery technology especially at low-power densities. A rectifying circuit is proposed with single high responsivity Schottky diode for RF–DC conversion. A matching circuit is optimized to improve not only the power transfer between the antenna and the diode, but also to reject harmonic signals. The radiating part is a monopole antenna, with a large bandwidth in the frequency domain and an omni-directional radiation pattern in the azimuthal plane. We show that antenna frequency response takes part in the improvement of the efficiency. The rectifier is integrated with the antenna on a printed circuit board, leading to 30% of size reduction with the same performance. The aim is to reach the highest efficiency with a single tone signal and a compact rectenna. This rectenna was simulated using both Agilent ADS and Ansoft HFSS software. An output DC voltage of 210 mV was measured inside an anechoic chamber which received a single tone signal of 2 µW/cm2 power density. The highest efficiency of 34% was obtained at a power density of 1.3 µW/cm2.