A study of reliable bio-telemetry, efficient powering and electromagnetic exposure in implantable neural systems

Purpose: This paper explores the bio-telemetry, powering and electromagnetic exposure design concerns in implanted neural systems. Methods: A class-E transmitter transfers PWM-ASK (Pulse-Width Modulated Amplitude-Shift Keying) modulated data signals to the brain implants at an optimal speed, while efficiently delivering sufficient power so as to keep the exposure of tissue to electromagnetic fields within tolerable limits. Results: A case study design illustrates that using a PWM-ASK modulated class-E transmitter, switching at a 5 MHz carrier frequency and requiring a voltage supply of 5 V, the maximal achievable data rate is equal to 168 kbps. Furthermore, two possible transmitter coil designs are proposed: simulations show that the minimal specific absorption rate (SAR) value when comparing these coils to power brain implants is equal to 1.72 W/kg for a transmitted power of 1 W per coil. Conclusions: This paper illustrates how the fundamental limits on the achievable PWM-ASK data transmission rate, as well as achievable bit error rate (BER) versus signal to noise ratio (SNR), can be improved using a Class-E transmitter design. Additionally, it has been shown which coil setups can be used so as deliver sufficient power to implants while keeping the exposure of tissue to electromagnetic fields at a minimum. © 2013 Korean Society of Medical and Biological Engineering and Springer.