An Inductively Coupled RF System for the Transmission of 1 kW of Power Through the Skin

In systems in which inductive coupling between a pancake-shaped coil on the surface of the body and a similar coil within the body is utilized for the transport of electromagnetic energy, the minimization of temperature rise in the tissue is intimately related to the achievement of minimum losses in the region of the implanted coil. A detailed theoretical analysis indicates the design considerations for achieving minimum losses in the vicinity of the implanted coil and predicts relevant internal losses of about one-half of 1 percent of the transported power. Experimental verification of theoretical expectations has involved an operating frequency of 428 kHz for the transmission of 1 kW of power between a simple water-cooled coil on the surface of the chest and a coil implanted in the chest wall of a dog. A maximum tissue temperature of 103.5° F was observed. Since 1-h operation per day at the 1-kW level would supply the anticipated energy requirements for a patient with an artificial heart, the system may find application in the charging of internal energy storage units of artificial heart systems.