Covert Body Area Network Using Electro-Quasistatic Human Body Communication

The transmitter (microcontroller) is excited with a pseudorandom binary sequence (PRBS) at 1 MHz, and using an oscilloscope and a telescopic antenna, the auto-correlation (\(\rho \)) between the known PRBS data sequence and the QSL signal is measured with varying distances (d) away from the body and two angles (\(\theta =0^\circ \): parallel to the antenna, \(\,\theta =90^\circ \): perpendicular to the antenna) between the device hand and the antenna, as shown in Fig. 2(a). From Fig. 2(c), it can be seen that while the QS leakage from the hand with unshielded EQS-HBC device is detectable up to ~0.5 m, EQS-HBC signals contained in the free hand does not leak beyond ~0.01 m, although both the hands contain the same amount of EQS-HBC signal (Fig. 3 – green curve). As the EQS-HBC transmitter on the device hand is brought in close proximity to the antenna (d  = 0+), the QS leakage is significant (−\(40\,dBm\)), as seen from Fig. 4.

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