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Fig. 7.
Effect of load impedance on the eciency of 5
th
stage of harvester circuit
Fig. 8.
Effect of load impedance on the eciency of 7
th
stage of harvester circuit
shown that eciency is better for input power -10 to 10dBm over[3]. Optimum
eciency is for input power -5 to 5dBm for 3-stage and 5-stage as shown in
Fig.6, 7 and for input power 0 to 10dBm for 7
th
stage as in Fig.8. From Fig.4
it is clear that output voltage is nearly equal to[3], but the output power is
increasing over[3] due to increased current arised at output terminal.
4 Conclusions
This paper introduces an RF energy harvester with tuned
ˀ
-matching circuit
for different stages and load variations. Simulation result of eciency and power
shows the improvement over existing harvester circuit. To obtain more improve-
ment in output voltage and power, multiple antenna or array of antenna can
be used but it will increase the size or cost of the circuit so for future work a
feedback circuit can be proposed that will improve the power and eciency.
