From the previous sections, the comparisons between the coil system and Hall Effect sensor system clearly points out the deficiency of Hall Effect sensor system.
Even through the coil system takes the advantages on the measured receiving power for it has bigger area to sense the magnetic flux, its volume is bigger than Hall Effect sensor.
There is a limit of application scenario in coil system for its huge volume.
The problem of Hall Effect sensor applied to communication system is that Hall Effect sensor generate too many noise to sense the signal. Reducing the noise, increased the sensitivity of Hall Effect sensor, and increasing the magnetic flux are possible methods to solve the problem.
First, reduce the noise generated from Hall Effect sensor. The noise of Hall Effect sensor is mostly generated from the power amplifier. For the current applications of Hall Effect sensor do not care about the noise as much as communication system. If the Hall Effect sensor can be customized for communication uses, its noise level may decrease a lot.
Second, increase the sensitivity of Hall Effect sensor. From the equation (30), received power is proportional to the squared sensitivity voltage. Increasing the magnetic sensitivity can increase the received power, but it may increase the noise as well. There is a tradeoff between received power and noise to get the best SNR.
Third, increase the magnetic flux. From equation (30), the more magnetic flux received, the higher received power. However, there is also a tradeoff between received power and noise, too. Because the more magnetic flux also means the more noise will be caught in receiver.
In the end, all the improving methods are based on the improvement of SNR. The best win-win situation is that increasing the received signal. Because the intensity of
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signal is high enough, there is no need for so many power amplifier. Then the noise generated from power amplifier can be reduced. In this way, the SNR of Hall Effect sensor may be rise sharply.
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Chapter 5 Conclusion
In this thesis, we investigated the feasibility of Hall Effect sensor applied in NFMIC systems. Hall Effect sensor system’s performance was measured to compare with coil systems. The received power equation of Hall Effect sensor system was derived for estimation. The measured results include the signal to noise ratio, power transfer function, and channel capacity. The deviations between measured results and derived equations are smaller than an order.
According to measurement results, the performance of Hall Effect sensor system is worse than coil system. The measurement results show that the noise in coil system is dominated by the back-end behind the coil, but the noise in Hall Effect sensor system is dominated by the Hall Effect sensor. It also shows the gap of received power between coil system and Hall Effect sensor system. Besides, the equation of the received power decay over distance in Hall Effect sensor system was derived to estimate how much power should be increased to reach the desirable transmission distance.
The limit of channel capacity of current Hall Effect sensor system is one tenth of coil system in the same transmission situation. Currently the existing Hall Effect sensor is not mainly used in communication applications, and there is still plenty of room for improvement of existing Hall Effect sensor. Hall Effect sensors can be improved by reducing the noise level and increasing sensitivity, operation frequency and sensed magnetic flux to have better performance.
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