1. IntroductionNowadays, digital electronic devices have been used to make many things easier and better. Personal computers have successfully managed to help people in their work and provide entertainment, so it is not surprising if now people are thinking about further incorporating electronic systems into the medical field, so that their service can be cheaper, easier accessible and of better quality to use. Some patients with chronic diseases sometimes need to be monitored closely by the medical team. By connecting patients to appropriate sensors capable of transmitting data over a network, it is possible for patients to have long-term monitoring without the need for a long and expensive stay in hospital. For long-term and long-distance monitoring, implantable sensors are desirable. Implantable sensors are inserted into the human body so that they do not disturb patients' activities. Of course, implanted devices should be able to communicate with the outside world without using wires because “wires passing through the skin are a source of infection, can cause injury (if pulled or hit), and are often uncomfortable for the patient” [ 1]. In addition to the monitoring purpose, implantable devices can also be used for more complex prescription applications, such as implantable drug delivery systems, implantable insulin pumps, and so on. Figure 1.1 Wireless Body Area Network The network for medical applications around the patient's body is defined as Wireless Body Area Network (WBAN), visible in Figure 1.1. A WBAN is composed of sensors (implanted or wearable) and a gateway node. The gateway node in the figure is called a Personnel Control Unit (PCU), although other terminologies such as Body Control Unit... in the center of the article... Nieto, Fundamentals and Applications of RFID Design. London: CRC Press, 2010.[7] Z. Yang et al, “Wireless Energy and Data Telemetry for Wearable and Implantable Electronic Devices,” Wireless Body Area Network: Technology, Implementation, and Applications (eds. Mehmet R. Yuce and Jamil Y. Khan), ISBN 978-981 -4241 -57-1. Singapore: Pan Stanford Pub., 2012.[8] W. Liu et al, “A neuro-stimulus chip with telemetry unit for retinal prosthetic device,” IEEE Journal of Solid-state Circuits, vol. 35, no. 10, October 2000.[9] MS Wegmueller et al, “Galvanic Coupling Enabling Wireless Implant Communications,” IEEE Transactions on Instrumentation and Measurement, vol. 58, no. 8, August 2009.[10] MS Wegmueller, Intrabody communication for biomedical sensor networks. (Doctoral thesis). 2007. Source: http://e-collection.library.ethz.ch/eserv/eth:29911/eth-29911-02.pdf