Key Technology Research On Implantable Nerve Simulator Powered By RF Energy

An implantable nerve stimulator powered by RF energy is proposed in this paper.It includes a RF energy harvester and an implantable nerve stimulator.The RF energy harvester consists of a number of antennas,and each antenna is cascaded by an impedence matching network and a multi-stage Villard doublers.The implantable nerve stimulator consists of a nerve stimulator and an external controller.The key technology of the RF energy harvester is how to improve both the output voltage and the energy conversion efficiency.A Multi-path Villard voltage doubler is designed for this purpose.The radio frequency signal received by the antenna is firstly fed to the impedance matching network and a two-stage voltage doublers,and then two of such paths are put into parallel to collect current,which is followed by a six-stage Villard voltage doublers to boost the voltage.Finally,the outputs of all the six-stage voltage doublers are paralleled to increase the overall current,and thereby improve the power conversion efficiency.The parameter of each component is determined by simulation with ADS.The RF energy harvester is tested both in air and in tissue.The key technology of the implantable nerve stimulator is the stimulus pulse generation circuit with high reability and stability.A bi-phase current stimulus pulse generation circuit is proposed.It can adjust the pulse amplitude by controlling the size of input H-bridge current.Both the duty cycle and frequency of the current stimulus pulse are adjusted by the PWM output from the MCU.A prototype is produced and tested.The test results show that for the RF energy harvester,when operating in the frequency with 2.4GHz with a transmitted RF power from 5dBm to25 dBm,the harvested voltage and the efficiency on a 1k?/ 10k?/ 90k? load are 0.05V-1.94V/ 4.73V/ 6.22 V and 0.005%-2%/ 1%/ 0.02%,respectively.While in the tissue(a piece of porch in this case),the harvested voltage and the efficiency on 1k? load is 0.01V-3.5V and 1.5%,respectively.The harvested voltage and efficiency of the proposed multi-channel RF energy harvester are about 2V and 1% higher than a single-antenna RF energy harvesting circuit,respectively.While for the implantable nerve stimulator,the stimulus pulse amplitude,frequency and the duty cycle are adjustable in the range of 10μA ~ 30 mA,1~300Hz,and 100μs ~1000μs,respectively.