A 2.016-Gb/s Crystal-Less IR-UWB Transceiver for Free-Moving Subject With High-Density Neural Implant

• Published in: IEEE journal of solid-state circuits pp. 1 - 14
• Main Authors: Lei, Jiaxin, Wu, Yusong, Liu, Xiliang, Zhang, Bingjing, Pei, Ruixuan, Zhang, Yuwei, Ma, Xiaoyan, Zhang, Milin
• Format: Journal Article
• Language: English
• Published: IEEE 2025
• Subjects: Brain-machine interfaces (BMIs); Clocks; Demodulation; hybrid modulation; impulse radio ultra-wideband (IR-UWB); Modulation; Neural implants; Power demand; Pulse width modulation; Signal to noise ratio; Symbols; transceiver; Transceivers; Wireless communication
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2025.3580081

This article presents a compact crystal-less impulse radio ultra-wideband (IR-UWB) transceiver designed for free-moving subjects with high-density neural implants. A six-order hybrid modulation scheme, combining differential 16-pulse-position modulation (D16PPM) and four-pulsewidth modulation (4PWM), is proposed, enabling a maximum data rate of 2.016Gb/s. An intra-pulse frequency hopping (FH) technique is proposed to precisely adjust the frequency variations within a single pulse, achieving a maximum transmitter (TX) radiation power of −7.6 dBm under the spectral mask. The all-digital TX consumes only 3.79 mW, resulting in an energy efficiency of 1.9 pJ/bit. A two-stage time-to-digital converter (TDC) is designed for the receiver (RX), featuring a sub-10-ps resolution and supporting both rising and falling edge conversions for the hybrid demodulation. With a power consumption of 17.1mW, the RX achieves an energy efficiency of 8.5 pJ/bit. The transceiver also incorporates a wireless clock calibration strategy, enabling a crystal-referenced external base station to wirelessly calibrate the clock frequency of the crystal-less implant. The calibration process completes within several microseconds, after which the implant can turn off the RX and the all-digital phase-locked loop (ADPLL) to reduce the power consumption. Ex vivo test demonstrates that the transceiver supports a transcutaneous transmission distance of 40 cm at 2.016 Gb/s and 120 cm at 1.344Gb/s, enabling the experimental subject to move freely within a meter-scale range while maintaining a Gb/s-level data rate.