This paper presents a new time-efficient modelling approach for UHF Dickson rectifiers. Due to the very low computation time, the approach can provide a quick and effective alternative to the standard transient simulations. The presented approach results in better estimation of the generated DC voltage and power conversion efficiency compared with the similar works in the literature. For the first time, an accurate mathematical relationship, including the non-zero reverse current, is expressed for finding the open load voltage of the Dickson rectifier while covering the broad range of RF amplitudes. The model uses the relation between the peak forward current and the load current to develop an input-to-output formula. Unlike the previous works, the channel length modulation is taken into consideration for the first time making the proposed model ideal for UHF Dickson rectifiers implemented with submicron CMOS transistors. Moreover, the proposed model takes secondary effects, such as the body effect and short-channel effects into account resulting in a more accurate estimation of the generated output DC voltage. Using the presented approach, a Dickson rectifier working at 900 MHz is implemented in a 0.18 mu m CMOS process. Good agreement between simulation results, predicted results, and measurement results is observed.