Combining Near-Field Over the Air (OTA) Measurements with Advanced Post-Processing Link Approach to Evaluate Specific Absorption Rate (SAR) for a Commercial Smartphone

The Specific Absorption Rate (SAR) using the Link approach has been researched and validated over the past few years for passive antennas and certain active devices. This paper extends the Link approach to measure SAR for a commercial smartphone, where there is no prior knowledge or control over the power control mechanism or the antenna's position within the phone. A 10MHz bandwidth LTE signal communication between a commercial smartphone and a Radio Communication Tester (RCT) simulating a mobile Base Station was studied in this work. The E-field distribution and SAR values derived from the Link approach were compared to results from the same Device Under Test (DUT) measured with a traditional SAR measurement system (single probe with a robot and phantom). The SAR value measured with 5mm separation between the DUT and the phantom are within 2.8% (or 0.12 dB) for 10g SAR. Using the SAR data at different separation distances, the SAR value at 0mm (contact position between DUT and Phantom) is evaluated using extrapolation from the Link approach. The 10g SAR results at 0mm are within 2.7% (or 0.11 dB) between the reference measurement and proposed Link approach. It's worth noting that only one measurement is required to evaluate the SAR at different distances and orientations, using the Link approach. Hence enabling the user to have a fast method at the early stage of development up to the pre-compliance stage for SAR assessment.