Efficient RF-to-DC Converters for Biomedical Implantable Devices

The power management section associated with the biomedical circuit is very crucial and should be optimally designed for optimal utilization of power. This work discusses the different power shaping or conversion circuits that had been taken for their performance analysis. The two-performance metrics power conversion efficiency and susceptibility against the wireless power transfer have been taken to investigate the operational performance of the biomedical circuits against the input signal strength and operating frequencies. Simulated results confirm the CNFET-based circuit performance is very good at a small value of input voltage 0.6V and a broad range of operating frequency (953 MHz). Therefore, a CNFET-based circuit can be used suitably in implantable devices with optimum power utilization and a remote powering mechanism over the RF link

RF energy harvesters for wireless sensors, state of the art, future prospects and challenges: a review

The power consumption of portable gadgets, implantable medical devices (IMDs) and wireless sensor nodes (WSNs) has reduced significantly with the ongoing progression in low-power electronics and the swift advancement in nano and microfabrication. Energy harvesting techniques that extract and convert ambient energy into electrical power have been favored to operate such low-power devices as an alternative to batteries. Due to the expanded availability of radio frequency (RF) energy residue in the surroundings, radio frequency energy harvesters (RFEHs) for low-power devices have garnered notable attention in recent times. This work establishes a review study of RFEHs developed for the utilization of low-power devices. From the modest single band to the complex multiband circuitry, the work reviews state of the art of required circuitry for RFEH that contains a receiving antenna, impedance matching circuit, and an AC-DC rectifier. Furthermore, the advantages and disadvantages associated with various circuit architectures are comprehensively discussed. Moreover, the reported receiving antenna, impedance matching circuit, and an AC-DC rectifier are also compared to draw conclusions towards their implementations in RFEHs for sensors and biomedical devices applications

SIMULATION ANALYSIS AND EXPERIMENTAL VALIDATION OF ULTRASOUND ENERGY TRANSFER IN THE NEAR FIELD TO CHARGE MEDICAL IMPLANTS

Acoustic power transfer technology is a method for wirelessly transfer energy to implantable medical devices. The advantage of ultrasonic power transfer over inductive power transfer is in the longer-distance range between the transmitter and receiver. Inductive power transfer is more powerful and even has high efficiency if the distance is in the order of the transmitter diameter orless. Nevertheless, in some cases short-distance ultrasonic power transfer may be employed; consequently, their operation may be complicated by the near-field aspects of acoustic energy transfer. Rapidly varying characteristics of the near-field region present challenges to experimental investigation.A piezoelectric energy transfer system consisting of two lead zirconate titanate (PZT) transducers is analyzed and tested, focusing on the near-field in this work. To facilitate this study, simulation analysis was used to investigate the effects on the voltage output of simultaneous variations of multiple pairs of physical parameters, such as changing the diameters of both receiver and transmitter. These physical parameters have been used to model, analyze, and simulate the performance of a piezoelectric ultrasonic energy transfer system using COMSOL Multiphysics software then validate experimentally. Moreover, the effect of the thickness ratio and diameter ratio on the power transfer efficiency was observed to be significant when the transmitter thickness was 1 mm. The simulation results indicated that changing multiple parameters simultaneously was more effective for energy transfer than changing individual parameters. The effects of operating frequency on power transfer efficiency at various distances between transmitter and receiver were also studied. It was found that the frequencies below 1 MHz showed almost zero power transfer efficiency regardless of the distance between two PZT transducers. The rotation angle that represents the misalignment between the PZT receiver and transmitter can make the power transfer efficiency change significantly by a few degrees. Finally, simulation analysis for influence of perfect match layers in terms of material and thickness on power transfer efficiency is provided