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Description
The traditional wireless communication based on electromagnetic waves face difficulties when functioning in the harsh environments like underground, submarine or biological tissues. These difficulties are due to the rapid attenuation of the radio wave in these media. The communication method based on the magnetic field is the alternative solution for such scenarios because the magnetic field can penetrate the non-magnetic materials such as water, sol.
A conventional magnetic communication system is based on the magneto-induction principle. It is typically composed of transmitting and receiving coils that ensure the communication by magnetic coupling. At relatively low frequencies (a few tens of kilohertz) and for a small size of the receiving coil, the sensitivity of the receiver decreases. In this case, a dedicated high sensitivity magnetic sensor could advantageously replace the receiving coil. Under some conditions, it is expected that such magnetic sensors should allow better sensitivity than a conventional coil. This improvement in the sensitivity offers an increase in the communication distance while ensuring reduced dimensions of the device. These characteristics are favorable for integration into numerous mobile applications.
The aim of this paper is to present a proof of concept of using a high sensitivity digital Giant Magneto-Impedance (GMI) sensor as a receiver in a magnetic communication system. The architecture of the system is presented in Fig.1. The transmitter is composed of a solenoid which creates a modulated On-Off-Keying magnetic field signal h at a carrier frequency $f_m$ = 60 kHz. This field is measured by an off-diagonal GMI sensor with a working frequency $f_0$ = 1 MHz. The induced voltage $v_{coil}$ across the pick-up coil of the sensitive element is modulated twice at $f_0$ and $f_m$.
Fig. 1 Structure of the communication system.
A double amplitude-demodulation is digitally performed in real time to recover the binary sequence of the transmitted message. The first demodulation, at $f_0$, is based on a synchronous detection and the second, at $f_m$, involves a digital envelope detector.
The experimental results showing the reliable functioning of the system, through the transmission of ASCII codes, will be presented. A second study will provide a comprehensive comparison of performances between this system and conventional magnetic communication systems. These performances include sensitivity, bandwidth, transmission distance, signal to noise ratio, etc.
References
[1] M. Muzzammil, N. Ahmed, G. Qiao, I. Ullah and L. Wan, "Fundamentals and advancements of magnetic-Field communication for underwater wireless sensor networks", IEEE Transactions on Antennas and Propagation., vol. 68, no. 11, pp. 7555-7570, Nov. 2020. doi:10.1109/TAP.2020.3001451
