A Bidirectional Passive BLE Chip for Battery-Free IoT Mesh Network

Battery-free tags offer a power-efficient solution for the wireless connection in Internet of Things (IoT), where the backscatter communication that is compatible with widely-deployed protocols such as Bluetooth Low Energy (BLE) significantly reduces the hardware cost thanks to the seamless integration into the existing infrastructure. However, there are three main shortcomings in the existing battery-free BLE tags: 1)The tag-to-access point (AP, uplink) communication ranges are limited to 97 meters at -10dBm incident power, which are not long enough for some outdoor scenes. 2) The AP-to-tag (downlink) communication in the state of the arts has not exceeded a 1Mbps data rate and a 4m range, disabling remote tag configuration. 3)The tag-to-tag communication has not been realized in a battery-free way, which cannot construct a passive IoT network. In this work, we demonstrate an integrated bidirectional passive BLE chip that conducts battery-free BLE communication in tag-to-tablet/smartphone, tablet/smartphone-to-tag, and tag-to-tag modes. The chip is implemented in a 65nm CMOS process. An all-digital intermediate frequency (IF) shaping technique is proposed to extend the tag-to-tablet/smartphone (uplink) communication range to 160m at$7.16\mu $W power consumption and a -10dBm incident tone. In addition, a$2^{nd}$-order intermodulation (IM2) based charge-domain GFSK demodulation technique is proposed to enable 1Mbps 12m downlink communication at$6.8\mu $W power consumption, which realizes both tablet/smartphone-to-tag and tag-to-tag communication in a fully battery-free way. As a result, the bidirectional passive BLE chip offers a potential solution for future battery-free IoT mesh network.