Electrical Power Transfer with “No Wires” - Energy Harvesting Autonomous Sensor Systems - page 201

Eciency vs. Frequency

120.00%

100.00%

80.00%

60.00%

40.00%

20.00%

0.00%

0.000001 0.0001 0.01 1 100 10000

Frequency (MHz)

FIGURE 6.16
Efficiency of a WPT system for various operating frequencies.

6.2.2.2 Simulation of Efficiency versus Coil Radius
Like the previous simulation, the same basic configuration of the two coils
was used except that the radius of the coils was changed between 5 and 100
cm. The range of different radii was chosen in conjunction with the needs
of various commercial applications, like miniaturized biomedical devices to
electric vehicles. For each coil radius, the efficiency curve is swept across a
frequency range of 1 to 1000 MHz as shown in Figure 6.17 .
Referring to Figure 6.17 , as the radius of the coil increased, it is observed
that the optimum efficiency band shifted towards the left of the figure and
widened. From this observation, it is notable that for any frequency between

Eciency vs. Coil Radius

120.00%

100.00%

80.00%

0.075 m
0.05 m
0.1 m
0.5 m
1 m

60.00%

40.00%

20.00%

0.00%
0.000001 0.0001 0.01 1 100 10000

Frequency (MHz)

FIGURE 6.17
Efficiency of a WPT system for various coil radii.