Geometry-based optimization of radio-frequency coils for powering neuroprosthetic implants

Two-Way Communication Digital Power Controllers for Wireless Retinal Prosthesis Systems

Power-efficient digital controllers are proposed for wireless retinal prosthetic systems. Power management plays an important role in reducing the power consumption and avoiding malfunctions in implantable medical devices. In the case of implantable devices with only one-way communication, the received power level is uncertain because there is no feedback on the power status. Accordingly, system breakdown due to inefficient power management should be avoided to prevent harm to patients. In this study, digital power controllers were developed for achieving two-way communication. Three controllers—a forward and back telemetry control unit, a power control unit, and a preamble control unit—operated simultaneously to control the class-E amplifier input power, provided command data to stimulators, monitored the power levels of the implanted devices, and generated back telemetry data. For performance verification, we implemented a digital power control system using a field-programmable gate array and then demonstrated it by employing a wireless telemetry system.

High-PSRR Wide-Range Supply-Independent CMOS Voltage Reference for Retinal Prosthetic Systems

This paper presents a fully integrated voltage-reference circuit for implantable devices such as retinal implants. The recently developed retinal prostheses require a stable supply voltage to drive a high-density stimulator array. Accordingly, a voltage-reference circuit plays a critical role in generating a constant reference voltage, which is provided to a low-voltage-drop regulator (LDO), and filtering out the AC ripples in a power-supply rail after rectification. For this purpose, we use a beta-multiplier voltage-reference architecture to which a nonlinear current sink circuit is added, to improve the supply-independent performance drastically. The proposed reference circuit is fabricated using the standard 0.35 µm technology, along with an LDO that adopts an output ringing compensation circuit. The novel reference circuit generates a reference voltage of 1.37 V with a line regulation of 3.45 mV/V and maximum power-supply rejection ratio (PSRR) of −93 dB.

Wide-Supply-Voltage-Range CMOS Bandgap Reference for In Vivo Wireless Power Telemetry

The robustness of the reference circuit in a wide range of supply voltages is crucial in implanted devices. Conventional reference circuits have demonstrated a weak performance over wide supply ranges. Channel-length modulation in the transistors causes the circuit to be sensitive to power supply variation. To solve this inherent problem, this paper proposes a new output-voltage-line-regulation controller circuit. When a variation occurs in the power supply, the controller promptly responds to the supply deviation and removes unwanted current in the output path of the reference circuit. The proposed circuit was implemented in a 0.35-μm SK Hynix CMOS standard process. The experimental results demonstrated that the proposed reference circuit could generate a reference voltage of 0.895 V under a power supply voltage of 3.3 V, line regulation of 1.85 mV/V in the supply range of 2.3 to 5 V, maximum power supply rejection ratio (PSRR) of −54 dB, and temperature coefficient of 11.9 ppm/°C in the temperature range of 25 to 100 °C.

Sleep in the United States Military

The military lifestyle often includes continuous operations whether in training or deployed environments. These stressful environments present unique challenges for service members attempting to achieve consolidated, restorative sleep. The significant mental and physical derangements caused by degraded metabolic, cardiovascular, skeletomuscular, and cognitive health often result from insufficient sleep and/or circadian misalignment. Insufficient sleep and resulting fatigue compromises personal safety, mission success, and even national security. In the long-term, chronic insufficient sleep and circadian rhythm disorders have been associated with other sleep disorders (e.g., insomnia, obstructive sleep apnea, and parasomnias). Other physiologic and psychologic diagnoses such as post-traumatic stress disorder, cardiovascular disease, and dementia have also been associated with chronic, insufficient sleep. Increased co-morbidity and mortality are compounded by traumatic brain injury resulting from blunt trauma, blast exposure, and highly physically demanding tasks under load. We present the current state of science in human and animal models specific to service members during- and post-military career. We focus on mission requirements of night shift work, sustained operations, and rapid re-entrainment to time zones. We then propose targeted pharmacological and non-pharmacological countermeasures to optimize performance that are mission- and symptom-specific. We recognize a critical gap in research involving service members, but provide tailored interventions for military health care providers based on the large body of research in health care and public service workers.