A Bidirectional, Full-Duplex, Implantable Wireless CMOS System for Prosthetic Control

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

• The work is currently limited to simulations and layout design. Is it possible to report some preliminary measurements on fabricated test blocks to strengthen the claims?
• The work focuses on circuit design, but implantable systems raise concerns about tissue heating, electromagnetic exposure, and long-term reliability. Have the authors estimated temperature rise under the chosen carrier frequencies and power levels?
• It is suggested that the authors discuss how the performance scales when more devices are connected.
• What is the expected maximum communication distance given the coil dimensions and frequencies used?
• After rectification and regulation, how much power is available for each neural front-end, and is this enough for common recording and stimulation tasks?

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks for the invitation to review this work. Battery-less implantable hub powered by inductive links (13.56 MHz for power + bidirectional comms; 27 MHz for high-speed uplink).

13.56 MHz carrier, half-duplex (106 kbps downlink, 30 kbps uplink) + power transfer. 27 MHz carrier, unidirectional uplink at 2.25 Mbps.

1. Figure 1 & 2: Identical captions ("Proposed architecture of external and implantable units") but appear to depict different subsystems (system-level vs. circuit-level). Clarify distinctions.

Figure 7: "out" signal in high-rate demodulation lacks units/description. Specify if it’s voltage or digital logic.

2. Equation (3): Symbols I1, I0, n, m undefined. Define terms (e.g., I1 = modulated current, I0 = reference current). Equation (4): Subscripts LV/HV not explained.
3. Abstract: "27 MHz carrier„" has stray character („). Section 2.1.2: "27 MHz carrier„" repeated typo.
4. Table 1: Uplink rate for this work listed as "30 kbps (@13M56) / 2Mbps (@27MHz)". Correct to "30 kbps (@13.56 MHz) / 2.25 Mbps (@27 MHz)" for accuracy. Missing units for "Coil config" (e.g., coil diameter/turns?).
5. Tuning Algorithm: Claims "maximizes rectified voltage" but lacks validation (efficiency vs. misalignment). Add simulation/data.
6. Regulator Efficiency: 70.5% is low for implantables. Justify trade-offs (e.g., quiescent current vs. load).
7. No analysis of noise tolerance or bit-error-rate (BER) in biological environments.
8. Conclusion: "New paradigm in neural prosthetic systems" is exaggerated. Acknowledge limitations (e.g., no in vivo validation, interference risks in multi-coil setup). No discussion of Specific Absorption Rate (SAR) or thermal effects for dual carriers (13.56/27 MHz).
9. Consider including citations of Exploration, 2024, 4, 20230146

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript presents a bidirectional, full-duplex implantable wireless CMOS system for prosthetic control, focusing on batteryless operation via inductive power transfer and dual-band communication. The work addresses critical challenges in implantable medical devices (IMDs), such as wireless power supply and bidirectional data transmission, which is relevant for neural prosthetics. However, several technical details, validation steps, and comparative analyses require further clarification.

1.Given the proximity of the two carrier frequencies (13.56 MHz and 27 MHz) and the conductive nature of biological tissues, have the authors evaluated electromagnetic interference (EMI) between the two links? 

2.The rectifier efficiency is reported as 95.1%, which is high. Please provide more details on the simulation conditions.  What is the typical load range of the four neural front-ends connected to the hub?

3.The linear regulator has an efficiency of 70.5%. Compared to switching regulators , why was a linear regulator chosen?

4.The automatic tuning algorithm is based on successive approximation. How many steps are required to converge? What is the power overhead of the tuning circuitry?

5.For the 13.56 MHz downlink, amplitude modulation changes the duty cycle from 50% to 25%. How robust is this modulation scheme to variations in link quality?

6.The high-bitrate uplink operates at 2.25 Mbps. What is the rationale for this specific data rate? 

7.The implantable unit layout is 0.99 × 0.2 mm. Does this include the coils? If not, what are the total dimensions including off-chip components? How does the size compare to other implantable systems?

8.The system is designed to manage up to four distributed front-ends. How are these front-ends wired to the hub, and what is the maximum distance allowed between the hub and front-ends without signal degradation? 

9. Figures 3–7 are referenced but not included in the submitted text. Please ensure all figures are provided with clear captions and are readable.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks for the invitation to review this work. The authors have solved the previous concern, and the article is recommended for publication.

Reviewer 3 Report

Comments and Suggestions for Authors

The author has addressed my issues.