A Miniaturized Dual Band Rectangular Spiral Loop Antenna for Biomedical Implants

Loop antennas have low specific absorption rate (SAR) and immune against the changes of the electrical properties of the human body. Electrically coupled loop antenna (ECLA) has been introduced as a dual for PIFA for single and multiband operation. To miniaturize ECLA, lumped capacitors have been used. However, this miniaturization technique has alignment problems, especially for multiband operation. Through this paper, a novel miniaturization technique is introduced. The proposed method depends on increasing loop inductance through wrapping another loop in addition to increasing matching capacitor which formed by the overlapped loops. The proposed antenna with size of 13×13×3mm3 has been simulated inside human head model and designed to operate at medical implants communications services (MICS) 402-405 MHz and industrial scientific medical (ISM) 2.4-2.48 GHz bands without lumped capacitors. The peak value of the 1 gm averaged SAR is 92.8 and 105.6 W/Kg whereas the peak realized gain is -29.5 and -22.5 dbi for both bands, respectively.