Implanted Antennas Designed to Monitor the Human Body

In-body medical devices such as pacemakers that use radiofrequency (RF) transmission may in future be equipped with implanted fiberoptic antennas.

Researchers from Queen Mary University (London, UK) and the UK National Physical Laboratory (NPL; Teddington, UK) have developed a prototype implantable radiofrequency identification (RFID) tag made up of a Planar inverted F antenna (PIFA) microstrip antenna that has been optimized to operate while embedded inside the human body. The device, which in essence is a very small RF-optical converter that reproduces the RF signal in full, has a minimal effect on the antenna performance. The antenna was tested in an artificially fabricated three-layer structure representative of skin, fat, and muscle; when comparing a hookup to both a standard coaxial cable and a fiberoptic set-up, the results showed that the use of the fiberoptic system could significantly decrease measurement errors by as much as 18 decibels (dB), by removing the effects of cable reflections, most notably the radiation of common mode current. The system was put to the test by the body-centric wireless sensor lab (BodyWiSe) at Queen Mary University. The breakthrough was achieved via a collaborative partnership with the optical communications company Seikoh-Giken (Matsudo City, Japan).

"This breakthrough could help the development of the next generation of miniature in-body technology designed to save even more lives," said NPL's principal research scientist Martin Alexander, Ph.D. "A miniature RF-optical transducer enables an optical fiber connection to the antenna, thereby eliminating the large distortion associated with the unwanted radiation from a coaxial cable."

Electrically small antennas for wireless communications applications can excite common mode currents on coaxial cables, producing unwanted radiation and with it distorted transmission results.

Related Links:
Queen Mary University
UK National Physical Laboratory
Seikoh-Giken