Abstract :
Many aspects of medicine now require monitoring of vital body functions and the stimulation of muscles or other organs. There is a limit to what can be detected from outside of the body, with ultrasound or X-rays so an implanted sensor is preferred that can monitor vital signs over a long period of time. Also restoring control to paralyzed muscles or helping an organ to function, such as the heart, can make a very big difference to the quality of life of otherwise ill or disabled patients. To get the best from these implants wireless communication is essential that can transfer data reliably, quickly and with least inconvenience to patents. Communication using an RFID technique has been used for some time but this has a limited data rate and requires a "wand" to be in close proximity to the patient. Using wireless communication a high data rate is possible, in both directions, enabling sensor data to be extracted and the performance of therapeutic implants to be optimised. For any in body system space and power are very limited so the communication system must fit into a small envelope. This make the implant antenna design critical with care being taken over the choice of materials. The electronics must also be very small to fit in with the primary implant function and its average current drain must be very low. The choice of frequency is defined by international agreement such that a patient with an implant will not encounter problems when he/she travels abroad. The communication system must be capable of large scale reliable manufacture in significant volumes to be of use to the many that it could benefit.
