Antennas for the latest implanted medical devices are being developed by Queen Mary University of London and tested through a unique piece of kit at the UK's National Physical Laboratory (NPL).
In the near future in-body medical devices such as pacemakers will use radio frequency (RF) technology to improve healthcare for patients. A low-powered, two-way wireless communications system linking an in-body device to a monitoring system can provide up-to-the minute patient data to allow doctors to adjust treatment as soon as it is needed. Devices will read data every night when the patient is asleep and send reports to the physician at the hospital, via the telephone system or Internet.
Antennas are vital to the operation of these systems. They need to be small, light, high performing but low-powered, have limited radiation directed at the wearer and be built into the implant. They also need to be made of a material that is biocompatible as well as a good electrical performer.
To ensure the wireless implants work with monitoring systems we need to be able to measure how the radio waves behave when transmitted. Coaxial cable is traditionally used to measure the performance of small electric antennas. However, electrically small antennas for wireless communications applications are can excite common mode currents on coaxial cables - producing unwanted radiation of common mode current and with it distorted results.
NPL , the UK's National Measurement Institute, has achieved a breakthrough in the non-invasive measurement of electrically small antennas. By connecting omni-directional antennas, to an optical fibre instead of a coaxial cable they were able to remove the effects of cable reflections and 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 of London led by Professor Yang Hao. Researchers Dr Marie Rajab, Dr George Palikaras and Andrea Sani have developed an implantable Radio Frequency Identification (RFID) tag made up of a PIFA antenna type that has been optimised to operate whilst embedded in an artificially fabricated three-layer structure representative of skin, fat and muscle.
The device was tested by both a standard coaxial cable and NPL's fibre optic set-up and the results were compared. The result showed that the use of the fibre optic system can significantly decrease measurement errors caused by flowing common mode currents, in this case by as much as 18 dB.
NPL's Martin Alexander, Principal Research Scientist, said:
"This breakthrough could help the development of the next generation of miniature in-body technology designed to save even more lives. NPL achieved it through a collaborative partnership with optical communications company Seikoh-giken. Together we developed a very small RF-optical converter which reproduces the RF signal in full and has a minimal effect on the antenna performance. A miniature RF-optical transducer enables an optical fibre connection to the antenna, thereby eliminating the large distortion associated with the unwanted radiation from a coaxial cable."
Joe Meaney, 0845 680 1864 firstname.lastname@example.org
Notes to Editors
National Physical Laboratory
The National Physical Laboratory (NPL) is one of the UK's leading science facilities and research centres. It is a world-leading centre of excellence in developing and applying the most accurate standards, science and technology available. NPL occupies a unique position as the UK's National Measurement Institute and sits at the intersection between scientific discovery and real world application. Its expertise and original research have underpinned quality of life, innovation and competitiveness for UK citizens and business for more than a century:
- NPL provides companies with access to world leading support and technical expertise, inspiring the absolute confidence required to realise competitive advantage from new materials, techniques and technologies
- NPL expertise and services are crucial in a wide range of social applications - helping to save lives, protect the environment and enable citizens to feel safe and secure. Support in areas such as the development of advanced medical treatments and environmental monitoring helps secure a better quality of life for all
- NPL develops and maintains the nation's primary measurement standards, supporting an infrastructure of traceable measurement throughout the UK and the world, to ensure accuracy and consistency.