I. Introduction
With the rapid development of the biomedical systems recently, many researchers are interested in designing the implantable bioelectronics devices such as cochlear implant, retinal prostheses, and muscular stimulation. Among the implantable bioelectronics devices, the demodulator block plays an important role to retrieve a serial bit stream along with a reference clock. Because of the implantationg consideration, all systems have external parts and internal parts in order to delivery the desired signals. The signals are designed to be modulated in the external parts.