Near-field dual-use antenna for magnetic-field based communication and electrical-field based distance sensing in mm3-class sensor node

This paper proposes a mm3-class dual-use near-field antenna that can be used for both magnetic-field based communication and electrical-field based distance sensing. The proposed antenna consists of two spiral coils, and they are used as a coil antenna in communication mode and signal electrodes in distance sensing mode. We evaluated the performance of the communication mode with a prototype antenna. The measured S21 is −8.3 dB to −45.1 dB in the range from 6 mm to 24 mm, which is highly correlated to 3D full-wave electromagnetic simulation. With this antenna, we performed BER evaluation with commercial transceiver boards showing that the proposed antenna could be used for ASK/OOK signaling. We also confirmed that the proposed antenna could be used for cm-scale node-to-node distance sensing through capacitive coupling.