Automated Optimization of Electronic Mode Stirring for Enhanced Backscatter Link Margin in Reverberant Cavities

In this paper, we present a series of experiments with a 2.4 GHz dual-polarized electronic mode stirring system for mitigating the dense multipath observed in biomedical telemetry within metal animal cages, including automated control over the mode stirring configuration. Four dual-polarized mode stirring antennas establish eight bits of digital control over the mode structure in a 0.2 m3 metal cage volume. With an optimized mode stirring configuration, we observe 26 dB improvement in the worst case one-way path loss across the 2400–2483 MHz band at 2,124 surveyed locations, sampled with a 1 cm grid on the floor of the cage. Using an example Bluetooth Low Energy link budget, we compare three automated mode stirring strategies for re-configuring the mode structure in response to simulated Brownian animal motion within the cage. Without mode stirring, the link budget has margin in only 68% of the surveyed locations, while with mode stirring, the link budget has margin in 99% of the locations in a stationary-animal scenario, and 92% of the animal locations in a moving-animal scenario. Finally, we present a demonstration of the link margin improvement in an actual communication link using a backscatter-based Bluetooth Low Energy implementation.