Design and Implementation of Multisite Stimulation System Using a Double-Tuned Transmitter Coil and Miniaturized Implants

This letter presents a double-tuned dual input transmitter coil operating at 13.56 and 40.68 MHz industrial, scientific, and medical (ISM) bands for multisite biomedical applications. The proposed system removes the need for two separate coils, which reduces system size and unwanted couplings. The design and analysis of the double-tuned transmitter coil using a lumped element frequency trap are discussed in this letter. The transmitter achieves measured matching of −26.2 and −21.5 dB and isolation of −17.7 and −11.7 dB at 13.56 and 40.68 MHz, respectively. A
$3\times15$
mm flexible coil is used as an implantable receiver. This letter shows synchronized multisite stimulation of two flexible implants at a distance of 2 cm while covered with 1 cm chicken breast.