Chapter 6 Conclusion and Future Work
6.2 Future Work
This paper introduces a telemetry which transmits data and power using one pair of coil. Our demodulator is design for low power consumption. We did not optimize the power efficiency, so in the future this system which is connected to a higher power efficiency rectifier will be a good issue.
Figure 72 shows the external and internal coils quality factor, we assume that the primary power is fixed. According to the power we want to receive and the rectifier input peak voltage to make VDC 1.8 volts, RAC is derived. Efficiency and channel capacity are estimated. For example, the primary power is set up to be 100mW. The rectifier efficiency is 85%, and the implant circuit power consumption is 40mW. The received power must be greater than 47.06mW=40mW /0.8. The other assumption is
that the distance of external and internal coil is fixed to be 1cm. The coupling coefficient is assumed to be 0.098. After these assumptions are set, we can run a MATLAB program to estimate the relation of Q1, Q2 and channel capacity by our equation in section 2.1.
Figure 72. (a) Relation of the Q1, Q2 and capacity (b) Relation of the Q1, Q2 and power efficiency
0
In order to reach higher power efficiency, the efficiency calculation must to be taken into account. The other MATLAB program is the relation of Q1, Q2 and power efficiency. After these two programs are obtained, we enter a threshold to run this program. If we want to make the power efficiency greater than 70%, and capacity is up to 500 kbps. This program will show the Q1 and Q2 value as shown in Figure 73, and two quality factor values are obtained. The only thing we have to do is choosing the coil size and material to meet the condition.
Figure 73. Reasonable Q1, and Q2 value with 500 kbps data rate and the 70% power efficiency 0
50
100
150
200
0 50 100 150 200
0 0.2 0.4 0.6 0.8 1
Q1=161, Q2=36 Efficiency > 70 Capacity > 500 kbps
Received power = 47.06mW
Q1 Q2
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