Unveiling the Device at ISSCC, San Francisco
In a groundbreaking presentation at the International Solid-State Circuits Conference (ISSCC) in San Francisco, a team of researchers introduced a device that marks a significant advancement in wireless communication technology. The device, a Wi-Fi-to-BLE tag, demonstrated battery-free frequency-division-duplex (FDD) communication with smartphones for the first time.
Tag Design and Functionality
The innovative tag is equipped with dual antennas, both of which facilitate power extraction from the incident Wi-Fi field. One of these antennas serves the dual purpose of receiving the Wi-Fi (802.11b) signal for decoding and clock-recovery, while the other manages Bluetooth using frequency-division-duplex communication.
The transmission of Bluetooth energy is back-scattered from the Wi-Fi field by correctly modulating a 50Ω load on the Bluetooth antenna. The team emphasized the first-time demonstration of the required phase-compensation in this project.
Innovative Processing Technique
Within the device, the received Wi-Fi signal is reprocessed using a pioneering ‘phase-flip’ tracking technique. This method demodulates the DBPSK Wi-Fi signal, generates a clean CW carrier signal for Bluetooth signal production, and recovers a 500kHz clock signal. The recovered clock signal is converted into a stable 8MHz system clock through an injection-locked ring oscillator.
Chip and Performance
The integrated circuit (IC) of the tag is built on a 65nm CMOS process and occupies a minimal surface area of 0.95mm2. The device is designed to operate both down-link and up-link at a speed of 1Mbit/s, with a maximum system power of 17μW.
In the prototype, Wi-Fi Ch7 (2.442GHz) energy was utilized to transmit data on BLE Ch39 (2.48GHz). This achievement is a testament to the potential of this technology in future wireless communication applications.
Key Contribution and Conclusion
The team’s ISSCC24 Paper 23.3, titled “A passive crystal-less Wi-Fi-to-BLE tag demonstrating battery-free FDD communication with smartphones,” marks a significant milestone in the field of wireless communication. The demonstration of battery-free FDD communication using this innovative device paves the way for the development of more energy-efficient wireless communication technologies in the future.
