A Passive IoT Bidirectional Tag Demonstrating 95m Downlink through Antenna-Array-Based Power-Data-Fusion Technique

The future boosting of loT applications is limited by the mW-level power burden of widely deployed wireless communication chips such as WiFi [1] and BLE [2]. As shown in Fig. 1 (top), the standby power leads to significant energy wastage in long-term loT sensors integrated with active radios. The traditional RFID-like devices offer a zero-standby wake-up solution [3], but the NFC suffers from ${\lt}10 \mathrm{~cm}$ short range and far-field RFID requires dedicated high-cost reader hardware. In recent years, battery-free techniques have been explored to support widely-used standards such as WiFi [4] and BLE [5], to realize seamlessly integration with the current infrastructure. Although the uplink channel has been extended to 160 m [6], the effective downlink range is limited to ${\lt}30 \mathrm{~m}$ [4–6] due to the poor sensitivity of power harvester based signal receiver.