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A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

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The schematic diagram of the bandgap voltage reference.
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f8-sensors-12-10292: The schematic diagram of the bandgap voltage reference.

Mentions: Bandgap voltage reference circuit uses the negative temperature coefficient of emitter-base voltage in conjunction with the positive temperature coefficient of emitter-base voltage differential of two transistors operating at different current densities to make a zero temperature coefficient reference. The structure [27] presented in this paper is depicted in Figure 8. The drain current of M1 and M2 is:(17)I=VEB1−VEB2R1+VEB1R3=VTln(n)R1+VEB1R3where VT is the thermal voltage, n is the area ratio of Q2 and Q1, R1 and R3 are the resistors shown in Figure 8, and VEB1 and VEB2 are the emitter-base voltage of the transistor Q1 and Q2, respectively. If the size of M3 is equal to the size of M2 and the effect of channel-length modulation is neglected, we can obtain the output voltage of the bandgap reference:(18)Vref=IR4=[VTln(n)R1+VEB1R3]R4=R4R3[VEB1+R3R1VTln(n)]where the temperature coefficient of VEB1 is negative and the temperature coefficient of VT is positive. The compensation of the temperature coefficientsVEB1 and VT is ensured by choosing values of n and of the R3/R1 ratio and the value of the output voltage is ensured by the R4/R3 ratio.


A wireless magnetic resonance energy transfer system for micro implantable medical sensors.

Li X, Zhang H, Peng F, Li Y, Yang T, Wang B, Fang D - Sensors (Basel) (2012)

The schematic diagram of the bandgap voltage reference.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472828&req=5

f8-sensors-12-10292: The schematic diagram of the bandgap voltage reference.
Mentions: Bandgap voltage reference circuit uses the negative temperature coefficient of emitter-base voltage in conjunction with the positive temperature coefficient of emitter-base voltage differential of two transistors operating at different current densities to make a zero temperature coefficient reference. The structure [27] presented in this paper is depicted in Figure 8. The drain current of M1 and M2 is:(17)I=VEB1−VEB2R1+VEB1R3=VTln(n)R1+VEB1R3where VT is the thermal voltage, n is the area ratio of Q2 and Q1, R1 and R3 are the resistors shown in Figure 8, and VEB1 and VEB2 are the emitter-base voltage of the transistor Q1 and Q2, respectively. If the size of M3 is equal to the size of M2 and the effect of channel-length modulation is neglected, we can obtain the output voltage of the bandgap reference:(18)Vref=IR4=[VTln(n)R1+VEB1R3]R4=R4R3[VEB1+R3R1VTln(n)]where the temperature coefficient of VEB1 is negative and the temperature coefficient of VT is positive. The compensation of the temperature coefficientsVEB1 and VT is ensured by choosing values of n and of the R3/R1 ratio and the value of the output voltage is ensured by the R4/R3 ratio.

Bottom Line: The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system.In addition, the output current varies with changes in the distance.The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

View Article: PubMed Central - PubMed

Affiliation: School of Electronics and Information Engineering, Beijing Jiaotong University, Beijing 100044, China. lixiuhan@bjtu.edu.cn

ABSTRACT
Based on the magnetic resonance coupling principle, in this paper a wireless energy transfer system is designed and implemented for the power supply of micro-implantable medical sensors. The entire system is composed of the in vitro part, including the energy transmitting circuit and resonant transmitter coils, and in vivo part, including the micro resonant receiver coils and signal shaping chip which includes the rectifier module and LDO voltage regulator module. Transmitter and receiver coils are wound by Litz wire, and the diameter of the receiver coils is just 1.9 cm. The energy transfer efficiency of the four-coil system is greatly improved compared to the conventional two-coil system. When the distance between the transmitter coils and the receiver coils is 1.5 cm, the transfer efficiency is 85% at the frequency of 742 kHz. The power transfer efficiency can be optimized by adding magnetic enhanced resonators. The receiving voltage signal is converted to a stable output voltage of 3.3 V and a current of 10 mA at the distance of 2 cm. In addition, the output current varies with changes in the distance. The whole implanted part is packaged with PDMS of excellent biocompatibility and the volume of it is about 1 cm(3).

Show MeSH
Related in: MedlinePlus