Ultra low power transceivers for wireless sensors and body area networks Abstract: A transceiver suitable for devices in wireless body area networks is presented. Stringent requirements are imposed by the high link loss between opposite sides of the body, about 85 dB in the 2. The receiver is fully integrated. The modulation is frequency shift keying, chosen because transmitters can be realized with high efficiency and low spurious emissions; a modulation index 2 creates a midchannel spectral notch.
The above observations infer that there exists an optimization between the size of the shield plane that can be directly connected to the transmitter ground, and rest of the shield plane connected to the ground plane through the high resistance R SN. Depending on the application and device form factor, the optimum shield sizes, pattern and ground plane size can be customized based on the fundamental understanding and models developed in this work.
Although auto-correlation serves for a fair comparison, it is an exaggerated attack model, since it only holds good for a known bit sequence. The distance is defined from the device hand. For WBAN, a 2. The closed loop in case of capacitively-coupled electro-quasistatic human body communication EQS-HBC is formed by the return path capacitance C gsh between the transmitter and receiver which is in the order of hundreds of femtofarads estimation of the return path capacitance C gsh is performed by connecting several known value capacitances C expt between the identical transmitter and the receiver device ground and measuring the loss for each case.
Since the return path capacitance has the highest impedance, the closed loop current is primarily determined by its value and is very weakly dependent on the forward path components.
Also, the received voltage is measured across the load, which is primarily capacitive C L due to the very high resistive component R L of the receiver input impedance. Variation of body impedance in the range of tens of Kiloohms does not affect the EQS-HBC received voltage since the load impedance Z L and the return path impedance values are orders of magnitude larger than the forward path body impedance.
Hence, the received EQS-HBC signal across the body will have the same value irrespective of the body conditions edematous or cachectic or different skin thickness, as long as it is terminated by a high impedance load. To conclude, this work for the first time, analyzes the security of electro-quasistatic human body communication EQS-HBC using the human body as the communication channel. The source of the information leakage is the EQS-HBC transmitter device aided by the human body that provides a low resistance closed path through the earth ground.
The Faraday cage, which acts as the shield for the transmitter, reduces the effect of the QS leakage from the standalone transmitter, but it serves as a ground plane to increase both the EQS-HBC received potential as well as the information leakage. A fascinating observation was that although the capacitive EQS-HBC signals from the device hand suffer low loss and maintain similar amplitudes at the receiving end, the QS leakage is negligible even very close to the receiving free hand, proving that the human body does not leak information.
De-coupling the shield and the ground of the transmitter using a high resistance reveals that both the QS leakage as well as the EQS-HBC received potential gets reduced.meoheajeswild.ga
An ultra low power baseband transceiver IC for wireless body area networks - Semantic Scholar
Hence, there exists an optimization between the area of the shield plane that connects directly to the transmitter ground potential, and rest of the shield connected to the ground plane through the high resistance R SN. In order to emulate a wearable device, the transmitter is battery-powered. A rechargeable Lithium ion battery is used as power supply.
The transmitter device was shielded using a copper-coated box to eliminate the QS leakage due to the standalone transmitter. The QS leakage from the device arm is measured with the device arm extended towards the antenna, and the distance d is measured between the antenna tip and the body-worn EQS-HBC device.
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The extension of the free arm towards the antenna during the leakage measurements ensure that any QS leakage from the device arm do not affect the measurements. Distance d is measured between the antenna and the device. Note that during the free hand leakage measurement, it is away from the body as well as the device hand to ensure that the leakage from the EQS-HBC device arm do not affect the free arm leakage measurements. It consists of the interfacing band with the copper electrode signal electrode which couples the transmitted signal into the body.
For safety analysis, only the transmitter is considered as the current distribution is mostly independent of the receiver high impedance termination. The transmitted signal needs to be biphasic to avoid any harmful electrochemical reactions A series coupling capacitor at the output of the transmit device, along with the interfacing copper electrode band capacitance C band formed between the transmit device and the human body provides the AC coupling, as shown in Fig. Hence, the signals are converted to AC, and contains both positive and negative phases.
D Tx is the on-body distance for signal transmission from the transmit device to the feet, which gives the voltage drop across the body V body. C band refers to the series coupling capacitor at the output of the transmit device along with the interfacing copper electrode band capacitance formed between the transmit device and the human body, D Tx denotes the on-body distance for signal transmission from the transmit device to the feet, which would give the voltage drop across the body V body. The safety limit analysis for the developed electric field across the human body is shown in Fig.
Also, the amount of current which is perceptible to a human is 1mA ac 25 , The ventricular fibrillation threshold is mA and a current of 2 A can cause a cardiac standstill and internal organ damage 25 , Hence, the current through the body during EQS-HBC is at least three orders of magnitude lower than the perceptible threshold.
The authors also confirm that informed consent was obtained from all participants for the experiments. Chen, Z. Stretchable conductive elastomer for wireless wearable communication applications. Huang, X. Rabaey, J. Hessar, M. Enabling On-body Transmissions with Commodity Devices. Yanagida, T. Human body communication system and communication device Hachisuka, K.
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- Ultra Low Power Transceiver For Wireless Body Area Networks Delgado Restituto Manuel Masuch Jens.
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