Implantable Medical Devices (IMDs), such as cochlear implants, retinal implants, neural recording devices, and deep brain stimulation systems, are placed inside the human body or brain and therefore require ultra-small size and extremely low power consumption. These stringent requirements can only be achieved through advanced IC design.

IMDs require essential blocks: 1) Wireless Power Transfer, 2) Forward Data Telemetry, 3) Backward Data Telemetry, 4) Neural Stimulation. Additional functionalities include neural recording, on-chip processing, and other system-level integration components.

1. Wireless Power Transfer (WPT)

IMDs can be powered by implanted batteries. However, batteries are typically bulky and require periodic surgical replacement, imposing a significant clinical burden. As an alternative, wireless power transfer (WPT) using implantable inductive coils offers a practical solution. A WPT system generally consists of two key blocks: a power amplifier (PA) outside the body and an AC–DC rectifier inside the body. Our research focuses on maximizing the efficiency of each block as well as optimizing overall system efficiency. In addition, we investigate optimization of coil structures while considering both implantation constraints and power transfer performance.

2. Forward Data Telemetry

In IMDs, operating settings such as stimulation intensity and the number of active channels often need to be adjusted, and these updates are performed using command data sent from outside the body. In such cases, forward data telemetry delivers these commands from outside the body to the inside while maintaining wireless power transfer simultaneously. Our research focuses on minimizing the power consumption of the telemetry block and ensuring robust data transfer, even under increased coil separation and angular misalignment.

3. Backward Data Telemetry

In many cases, data acquired by IMDs, such as neural recording data, must be transmitted outside the body for further processing. In such situations, backward data telemetry is required to send the acquired data from inside the body to the outside while maintaining wireless power transfer. Our research focuses on increasing the data rate and lowering the bit error rate (BER). Furthermore, we investigate full-duplex data telemetry, where forward and backward data transmission occur simultaneously while wireless power transfer is continuously maintained.

4. Neural Stimulation

Neural stimulation, including deep brain stimulation, is required to treat neurological disorders such as Parkinson’s disease and epilepsy by targeting deep brain regions like the thalamus. In this approach, predetermined electrical charges are delivered to the target area. This stimulator is powered by the WPT block and operates together with forward and backward data telemetry. Our research focuses on improving overall system efficiency, including both AC-DC rectifier and neural stimulation.

Implantable Medical Devices (IMDs), such as cochlear implants, retinal implants, neural recording devices, and deep brain stimulation systems, are placed inside the human body or brain and therefore require ultra-small size and extremely low power consumption. These stringent requirements can only be achieved through advanced IC design.

IMDs require essential blocks: 1) Wireless Power Transfer, 2) Forward Data Telemetry, 3) Backward Data Telemetry, 4) Neural Stimulation. Additional functionalities include neural recording, on-chip processing, and other system-level integration components.

1. Wireless Power Transfer (WPT)

IMDs can be powered by implanted batteries. However, batteries are typically bulky and require periodic surgical replacement, imposing a significant clinical burden. As an alternative, wireless power transfer (WPT) using implantable inductive coils offers a practical solution. A WPT system generally consists of two key blocks: a power amplifier (PA) outside the body and an AC–DC rectifier inside the body. Our research focuses on maximizing the efficiency of each block as well as optimizing overall system efficiency. In addition, we investigate optimization of coil structures while considering both implantation constraints and power transfer performance.

2. Forward Data Telemetry

In IMDs, operating settings such as stimulation intensity and the number of active channels often need to be adjusted, and these updates are performed using command data sent from outside the body. In such cases, forward data telemetry delivers these commands from outside the body to the inside while maintaining wireless power transfer simultaneously. Our research focuses on minimizing the power consumption of the telemetry block and ensuring robust data transfer, even under increased coil separation and angular misalignment.

3. Backward Data Telemetry

In many cases, data acquired by IMDs, such as neural recording data, must be transmitted outside the body for further processing. In such situations, backward data telemetry is required to send the acquired data from inside the body to the outside while maintaining wireless power transfer. Our research focuses on increasing the data rate and lowering the bit error rate (BER). Furthermore, we investigate full-duplex data telemetry, where forward and backward data transmission occur simultaneously while wireless power transfer is continuously maintained.

4. Neural Stimulation

Neural stimulation, including deep brain stimulation, is required to treat neurological disorders such as Parkinson’s disease and epilepsy by targeting deep brain regions like the thalamus. In this approach, predetermined electrical charges are delivered to the target area. This stimulator is powered by the WPT block and operates together with forward and backward data telemetry. Our research focuses on improving overall system efficiency, including both AC-DC rectifier and neural stimulation.