Body Proximity Detection based on Reflections of Multi-Antenna Uplink Transmission from a 5G Mobile Handset

A cost-effective method for detecting the proximity of a human body to a mm-wave 5G mobile device is demonstrated. It is intended to ensure that the device’s transmissions meet the regulatory limits for human exposure defined for this frequency range, while also minimizing the reduction in uplink throughput that this may necessitate. The method is demonstrated in a commercial FR2 phased-array front-end module, where the power fed to the antenna in each transmission path, as well as the power reflected from it, are monitored via built-in power detectors. Essentially, the impact of the nearby body on the active S-parameter characteristics across the beamforming phased array elements is exploited, thus realizing joint communications and sensing without involving dedicated hardware for the detection. Analysis and experimental results are provided, demonstrating that reliable detection of the human body within the range of distances of interest up to 20 mm can be achieved.