title: RF communication with implantable wireless device: effects of beating heart on performance of miniature antenna.
abstract: The frequency response of an implantable antenna is key to the performance of a wireless implantable sensor. If the antenna detunes significantly, there are substantial power losses resulting in loss of accuracy. One reason for detuning is because of a change in the surrounding environment of an antenna. The pulsating anatomy of the human heart constitutes such a changing environment, so detuning is expected but this has not been quantified dynamically before. Four miniature implantable antennas are presented (two different geometries) along with which are placed within the heart of living swine the dynamic reflection coefficients. These antennas are designed to operate in the short range devices frequency band (863-870 MHz) and are compatible with a deeply implanted cardiovascular pressure sensor. The measurements recorded over 27 seconds capture the effects of the beating heart on the frequency tuning of the implantable antennas. When looked at in the time domain, these effects are clearly physiological and a combination of numerical study and posthumous autopsy proves this to be the case, while retrospective simulation confirms this hypothesis. The impact of pulsating anatomy on antenna design and the need for wideband implantable antennas is highlighted.
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK.
authors.forename: Olive H
authors.initials: OH
authors.lastname: Murphy
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Borghi
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Bahmanyar
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK.
authors.forename: Christopher N
authors.initials: CN
authors.lastname: McLeod
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK ; Heart Science Centre , Harefield Hospital , Hill End Road , Harefield , Middlesex UB9 6JH , UK.
authors.forename: Manoraj
authors.initials: M
authors.lastname: Navaratnarajah
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK ; Heart Science Centre , Harefield Hospital , Hill End Road , Harefield , Middlesex UB9 6JH , UK.
authors.forename: Magdi
authors.initials: M
authors.lastname: Yacoub
authors.affiliation: Department of Electrical Engineering , Institute of Biomedical Engineering , Centre for Bio-Inspired Technology , Imperial College London , SW7 2AZ , UK.
authors.forename: Christofer
authors.initials: C
authors.lastname: Toumazou
keywords: RF communication; beating heart effects; biomedical communication; cardiology; cardiovascular pressure sensor; dynamic reflection coefficients; frequency response; human heart; implantable antenna; implantable wireless device; miniature antenna; posthumous autopsy; power losses; surrounding environment; wearable antennas; wideband implantable antennas; wireless implantable sensor