Dual Band, Miniaturized, Implantable Antenna Design with On-body Antennas for Wireless Health Monitoring

A modified Hilbert fractal geometry and serpentine radiator-based implant antenna is proposed for dual band medical operations in both the MICS band (402-405 MHz) and ISM band (2.4-2.48 GHz). The antenna has miniaturized dimensions of 5.5 x 7.6 x 0.8 mm(3) (width x height x thickness) and is simulated inside a four layer (air, skin, fat and muscle) model with dimensions of 150 mm x 75 mm x 55 mm. A Zirconia (epsilon(r)=29) superstrate and shorting pin were utilized to achieve biocompatibility and the desired resonance. Relatively stable and omni-directional radiation patterns were achieved for the dual band operation. An ISM band on-body antenna (5.8 x 5.5 x 0.8 mm(3)) was proposed to generate a wake-up signal while the wireless telemetry transmission was achieved using the MICS band onbody antenna (5.8 x 5.5 x 0.8 mm(3)). Implant and on body antennas demonstrated a reflection coefficient (S-11) better than -10 dB characteristics. To adhere to the SAR regulation limit of 1.6W/kg, the peak incident power should not exceed 0.25 mW and 0.2 mW for the ISM band and MISC band on-body antennas respectively. Propagation channel characteristics were simulated by observing the S-12 and S-13 characteristics and satisfactory results were achieved. The peak gain for the implant, MICS band and ISM band on-body antennas were -39.8 dBi, -35.6 dBi and -23 dBi, respectively due to the miniature dimensions. The miniaturized characteristics, dual-band operation, biocompatibility and stable characteristics in the presence of human tissue model make both the implant and on-body antennas suitable for biomedical monitoring systems.