A 200Mb/s inductively coupled wireless transcranial transceiver achieving 5e-11 BER and 1.5pJ/b transmit energy efficiency

Recent advancements in medical neural science and brain research have enabled the potential of uninterrupted simultaneous recording of thousands of neurons. To minimize the risk of infection to the patients, wireless data transmission is the preferred option. Therefore, the large amount of data generated by the neural recorder must be transmitted through the scalp and skull bone to an outside data processor to translate into action or to be analyzed. A next-generation 1024-channel implanted neural recorder that uses 20KS/s 8b ADC to capture action and field potential can generate up to 164Mb/s data, which imposes a stringent requirement on the communication throughput of the implanted transmitter (TX). In addition, TX power consumption must be kept as low as possible for longer battery life or safe wireless power transfer, while the power consumption of the receiver (RX) chip outside the scalp can be relaxed. Current state-of-the-art designs that use backscattering [1], pulse harmonic modulation (PHM) [2] or ultra-wide-band (UWB) communication [3,4] suffer either from limited throughput or low TX energy efficiency. Other techniques such as ultrasound [5] usually have data-rates limited to tens of Kb/s and do not penetrate through the skull. In this paper, we utilize inductive coupling for transcranial wireless data transfer to achieve 200Mb/s data-rate and ultra-low TX power. Series de-Q resistors are employed to alleviate inter-symbol-interference (ISI) caused by the inductor self-resonance. The entire TX chip uses a single 0.5V Vdd to save power. To generate 200MHz TX clock from 10MHz reference at such low supply, an injection-locked PLL with fully digital frequency tracking and spur suppression is used.