A helical folded dipole antenna for implantable communication devices

Implantable devices have been investigated with a great interest as communication tools. These implantable devices are embedded into the human or animal body. The vital information (e.g., glucose, blood pressure, and temperature) can be transmitted from implantable devices to the external equipments through wireless communication link [1]– [3]. Figure 1 shows a one of the application for a human in a sickroom. By using an implanted device, patient's events can be detected immediately. Then the implanted device sends the alert wirelessly to the home appliance which is connected to a hospital information system via a secured network link. A physician receives the alert and can decide to check back with the patient. In general, the implantable devices is have a bidirectional radio that can communicate with a paired radio carried within an external appliance. The external appliance could be a home monitoring device or a portable equipment, such as a cell phone, that provides the patient with increased mobility and a short-range wireless communication [4]. Therefore, the antenna for implanted devices is a key components in these telemetry systems. There are several issues to be considered in the design of an in-body antenna, including power consumption, size, frequency, biocompatibility, etc. This paper proposes an implanted helical folded dipole antenna for a short-range wireless communication at 2.45 GHz. Moreover, the implantable device is supposed to be embedded into human body using a syringe. According to this demand, the proposed antenna has a circular cylindrical shape of 1-mm diameter and 17.7-mm length. The antenna performances were investigated by use of the finite-difference timedomain (FDTD) calculation.