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A simple and a straightforward mathematical modeling of the eddy current generated on a retarded rotating disk (RD) is proposed in this paper. First, the braking magnetic force, which curbs the movement of the disk is evaluated using the basic laws of electromagnetism. Second, the braking torque is related to the braking force through a polynomial function. Third, the equation of motion is derived considering the nonlinear behaviour of the aerodynamic drag forces. The proposed model is validated experimentally for constant and alternating magnetic flux profiles with best fit rates (BFRs) more than 85% and 93% for both rotational velocity and braking torque, respectively. Programmable braking application is demonstrated using the proposed approach and its applicability is verified experimentally.

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A triple-band Electrically Coupled Loop Antenna (ECLA) is designed to operate in the three standard bands for biomedical implantation purposes: Medical Implant Communications Services (MICS) (402–405 MHz), Wireless Medical Telecommunication Services (WMTS) (1395–1405 MHz) and Industrial, Scientific, and Medical (ISM) (2400–2480 MHz). An equivalent circuit is derived for the multiband ECLA based on simple equations relate the dimensions with the circuit parameters to get a good understanding of antenna operation as well as saving time in simulations. The proposed antenna size is 15 × 13.8 × 13 mm3 and simulated in a muscle phantom with size 100 × 100 × 100 mm3. The calculated peak realized gain values are − 18, − 30 and − 33.3 dBi and the peak 10 g averaged Specific Absorption Rate (SAR) values are 11.59, 43.07 and 49.75 W/Kg for the three bands, respectively. A detuning study is carried out to ensure that the proposed antenna is robust against electrical properties variation thus it can be implanted in different tissues of different people in various health circumstances. Two antenna prototypes have been fabricated and tested in a solution that mimics human tissue.

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