Miniaturized Circularly Polarized Loop Antenna for Biomedical Applications

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Abstract
A novel circularly polarized antenna is proposed at 902-928 MHz Industrial, Scientific, and Medical band for implantable applications. By properly positioning the feed and shorts, either right-hand circular polarization property or left-hand circular polarization property can be realized. Slow wave concept is utilized by loading patches to the radiated loop antenna to achieve miniaturization. Thus, a compact size of 13 mm × 13 mm × 1.27 mm is obtained. Compared to the unloaded loop antenna of the same size, the centre frequency shifts from 1.93 GHz to 882.5 MHz, which suggests a miniaturization of 54.4%. The simulated results show that a wide bandwidth of 18.2% can be realized with |S 11 | below -10 dB and axial ratio below 3 dB. The simulated realized gain is -32 dBi at 915 MHz. The measurement is carried out in both skin-mimicking gel and pork, and a bandwidth of 27.8% and 29.4% can be achieved with |S 11 | below -10 dB, respectively. The measurement of |S 21 | reveals that circular polarization can be obtained for the proposed configuration.
Funding Information
  • National Natural Science Foundation of China (61372012)
  • National Research Foundation, Singapore (NRF-CRP10-2012-01)

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