This paper presents a compact high-efficiency broadband microwave rectifier for free-space Radio Frequency (RF) energy harvesting. Lumped-element components and voltage-doubling circuits are used to improve output efficiency and power, widen frequency bandwidth, and reduce circuit size. The theoretical model and numerical model of the rectifier circuit are established, and the mechanism of the microwave voltage-doubling rectifier is revealed by using Advanced Design System (ADS) EM simulator. The simulated results exhibit that the rectification efficiency is larger than 60% with the highest efficiency of 84% under the input power of 16 dBm–30 dBm and the frequency of 600 MHz–1600 MHz. Moreover, the overall size is 4 cm × 2 cm, smaller than some recently published literatures, proving the circuit structure’s superiority. On this basis, for the lower operating frequency band, the circuit structure is further simplified without reducing bandwidth and efficiency by reducing the number of circuit components, and the overall size is only 2 cm × 2 cm. For validation, two broadband rectifiers fabricated by utilizing FR4 dielectric substrate and Printed Circuit Board (PCB) technology, are implemented and tested using Vector Signal Generator (VSG), DC resistance, and multimeter. The measure results are in good agreement with simulation ones within the measuring range of the equipment.