Very High Bit Rate Near-Field Communication with Low-Interference Coils and Digital Single-Bit Sampling Transceivers for Biomedical Sensor Systems

Abstract

The evolution of microelectronics increased the information acquired by today’s biomedical sensor systems to an extent where the capacity of low-power communication interfaces becomes one of the central bottlenecks. Hence, this paper mathematically analyzes and experimentally verifies novel coil and transceiver topologies for near-field communication interfaces, which simultaneously allow for high data transfer rates, low power consumption, and reduced interference to nearby wireless power transfer interfaces. Data coil design is focused on presenting two particular topologies which provide sufficient coupling between a reader and a wireless sensor system, but do not couple to an energy coil situated on the same substrate, severely reducing interference between wireless data and energy transfer interfaces. A novel transceiver design combines the approaches of a minimalistic analog front-end with a fully digital single-bit sampling demodulator, in which rectangular binary signals are processed by simple digital circuits instead of sinusoidal signals being conditioned by complex analog mixers and subsequent multi-bit analog-to-digital converters. The concepts are implemented using an analog interface in discrete circuit technology and a commercial low-power field-programmable gate array, yielding a transceiver which supports data rates of up to 6.78 MBit/s with an energy consumption of just 646 pJ/bit in transmitting mode and of 364 pJ/bit in receiving mode at a bit error rate of 2×10−7, being 10 times more energy efficient than any commercial NFC interface and fully implementable without any custom CMOS technology.

Simultaneous Power Feedback and Maximum Efficiency Point Tracking for Miniaturized RF Wireless Power Transfer Systems

“…For the primary-side controller, the processing time shows a significant duration of 150 µs with a period of 1 ms, running along the main configuration task. Wireless communication: Here, the primary side is in permanent reception mode, while the secondary side sends packets including 4 bytes of measurement data every 1 ms. Two alternatives are outlined: the off-the-shelf 2.4 GHz transceiver integrated into the given wireless microcontroller (with an output power level of 0 dBm and a custom protocol with minimal overhead) versus the custom low-power near-field communication (NFC) system published by the authors of this work in [ 33 ]. The custom NFC system operates at a carrier frequency of 13.56 MHz and is therefore situated below the energy carrier of 40.68 MHz, so that no harmonics of the WPT interface fall into the communication band.…”

Novel Resonance-Based Wireless Power Transfer Using Mixed Coupling

“…The real and imaginary parts of this input impedance can be graphed as shown in Figure 5. According to (15), if the resistance R is neglected, the series and parallel resonance frequencies will be respectively derived as follows.…”

“…NFC uses a magnetic field coupling having a resonance frequency of 13.56 MHz [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. In the resonance-based IPT using 6.78 MHz as the operating frequency, the harmonic component causes the problem of electromagnetic interference to NFC [ 15 , 16 , 17 ]. We can solve the problem of electromagnetic interference with NFC by using the electric coupling method, such as CPT.…”

Comparative analysis of energy transfer mechanisms for neural implants

“…NFC stands apart due to its specific design for short-range, high-frequency communication and power transfer. This specialized design results in NFC devices generating weaker electromagnetic fields compared to broader RF technologies, whose radiation levels vary based on power and application ( Stoecklin et al, 2020 ; Lathiya and Wang, 2021 ; Van Mulders et al, 2022 ).…”

“…Moreover, NFC’s capability to support two-way data communication between an external coil or loop antenna and a second implanted coil, while penetrating the tissue barrier, further sets it apart. This dual functionality for both power transfer and data exchange at close proximity makes NFC a versatile choice for neural implant systems, serving specific purposes that broader inductive coupling technologies might not fulfill ( Stoecklin et al, 2020 ; Lathiya and Wang, 2021 ; Van Mulders et al, 2022 ).…”