Wearables for Joint Effusion Detection: An Analysis for Magnitude-/Phase-Only vs. Combined Readings

Detecting and diagnosing joint effusion is a costly and often invasive process. Our previous work introduced a seamless wearable system consisting of transmit and receive loops that was able to detect changes in synovial fluid build-up via transmission coefficient $\boldsymbol{(\mathrm{S}_{21})}$ measurements. The system relied on magnitude and phase measurements conducted each at different frequencies. This work simplifies the previous design by enabling monitoring of both magnitude and phase at a single frequency. Another improvement is the elimination of any lumped elements attached to the loops to ease the wearable implementation. Our studies provide an optimal design at 1485.2 MHz that is robust to frequency fluctuations within a bandwidth of 30 MHz. Key performance metrics are identified and compared for magnitude-Iphase-only designs vs. the proposed combined approach.