Rectifiers are important energy converters and henceforth crucial building blocks for RFID applications. In the first half of the work, we have presented a design methodology for matching the rectifier input impedance with the antenna to maximize the rectifier power conversion efficiency. The proposed design approach uses the fundamental transconductance (Gm(1)) analysis to estimate the rectifier input impedance. In the second half, a comparison between various possible single-stage rectifier topologies implemented in a CMOS 0.18 mu m technology operating at UHF-band is presented. Using voltage conversion efficiency as the FOM, the optimum rectifier topology for RFID application is determined.