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An improved RF-dc converter based on a class-E rectifier with wide-dynamic-range input matching is presented. The input impedance is controlled by two varactor diodes to compensate for impedance changes with RF input power and dc loading conditions. The RF-dc converter achieved a peak efficiency of 60% and an S11 less than - 20 dB over an input RF power range of 12 dB and an operating battery voltage of 2.5-4.2 V at 800 MHz. An analytical model for input impedance and efficiency was developed and shown to match simulation and measurement results.