Input voltage levels are low; so threshold voltage
modulation scheme is needed.
External bias voltage is not available.
The frequency of operation is high; therefore parasitic
capacitance of MOSFETs is major source of loss in the
circuit.
The circuit should be dissipating minimum power to
increase the overall system efficiency.
Schottky diode has a low threshold voltage, less series
resistance and junction capacitance, compared to P-N diodes.
However it is not available in standard CMOS processes due
to the particularity in manufacturing process, which causes a
fabrication overhead. Many rectifier topologies [6-7] have
been proposed using MOS transistors. However there are
major issues for RF energy harvesting applications, some of
these are as follows.