Research and Development towards Wirelessly Powered Bidirectional Chip for Biomedical Applications

Medical-use-motivated wireless energy transfer via coupled resonances has been one among the hot topics in bioelectronics. Making breakthrough in either avoiding battery replacement of next-generation invasive medical therapy or harvesting surrounding natural power sources relies on its improvement. Truly light-weight and wireless capabilities are of primary importance in portability, where fully integrated circuits techniques are essential to advance ultimate goal- “single-chip” system(s). Unfortunately, known AC-DC conversion core used for medical systems, the rectifier, requires low dropout diode(s) implemented in custom-made devices to enhance conversion efficiency, unfavorable for System-on-a-Chip (SoC) purpose. Such a technical problem creates possibility of further circuit design optimization without non-standard CMOS devices. On the other hand, in addition to achieve both the SoC purpose and good conversion efficiency, it is important to have back telemetry mechanism to send real-time recorded physiological information outside body and real-time electrode-tissue interfacing information to examiner. For invasive applications, such a mechanism can be used to let physician know the internal status, thereby avoiding regretable matter. For noninvasive applications, it can be used to monitor device-skin connection in a way real-time. Known low-complexity electrical back telemetry mechanism uses so-called “load” modulation technique. The technique is disadvantageous to system energy efficiency. In addition, it is unavoidable to cost considerable silicon area to realize the technique so far, no matter what kind of loading variation being considered for the back telemetry. As a result, the technique is not suitable for avoiding the battery replacement and being applied to portable light-weight body area network (BAN). Finally, one should consider the receivability of wirelessly incoming command data which is important to medical applications such as implantable systems. For low-power design aspect, low-complexity binary modulation has been widely adopted. It is, however, the area required to implement the filter is considerable, as a result of restricted carrier frequencies for medical applications. In view of the above, this project aims at investigating the best design of the rectification core fulfilling optimal technical combination of achieving low loss, low cost suitable for on-chip implementation, and energy-efficient back telemetry with robustness for the AC-DC conversion.

Project ID:PB10210-0078
External Project ID:NSC102-2218-E182-003