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Performance measures of implant antennas

In English

Författare

Summary, in English

Modern electronic medical implants have reached a high degree of complexity. This has increased the demands on the communication link with the implant, both regarding the bandwidth and the communication distance. A medical communication system at RF frequencies has been standardised, the Medical Implant Communication System (MICS), which use a frequency allocation of 402 - 405 MHz. This frequency band is allocated for implant use both and the US and in the EU. The EIRP is limited to -16 dBm in order to reduce the interference to existing users of the same frequency band. This low EIRP makes it necessary to have reasonable effective antennas in the implants in order to get a benefit form the switch from the classical inductive link to RF. The normal performance measures of antennas have to be modified when applied to implant antennas. The reflection coefficient S11 and the VSWR are straightforward to use also in the implant case. But the gain definition is only valid in a lossless medium. This is not a problem for the implanted antenna, as it is placed in a finite body, i.e. the patient. The implant and the body carrying it will act as one larger antenna, and will have a measurable gain according to the classic definition. The drawback is that the gain will depend heavily on the size and shape of the body, which makes it hard to give a generic value for the gain from a certain antenna. The type of antenna and the amount of isolation around the antenna will influence the amount of nearfield losses, and thus the efficiency. There is a modification of the efficiency measure which solves the problem of the gain definition in an infinite lossy medium [the]. This efficiency measure is a candidate for a quality measure of implanted antennas. The efficiency of an antenna in an infinite lossy material is evaluated by calculating the integral of the Poynting vector over a closed surface in the far zone of the antenna.

Publiceringsår

2006

Språk

Engelska

Publikation/Tidskrift/Serie

European Space Agency, (Special Publication) ESA SP

Volym

626 SP

Dokumenttyp

Konferensbidrag

Förlag

European Space Agency

Ämne

  • Electrical Engineering, Electronic Engineering, Information Engineering

Nyckelord

  • Implant antennas
  • Medical communication system
  • Frequency band

Conference name

European Conference on Antennas and Propagation: EuCAP 2006

Conference date

2006-11-06 - 2006-11-10

Conference place

Nice, France

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 1609-042X
  • ISSN: 0379-6566