Simultaneous Specific Absorption Rate Ratio Summation and Peak Location Separation
Exceeding simple SAR summation thresholds requires peak location separation ratios below 0.04 to avoid multi-thousand-dollar volumetric chamber testing.
10g Extremity SAR
Meaning
Specific absorption rate safety metric for localized radiofrequency energy absorption in human limbs during wireless device operation. Compliance with 10g extremity sar requires that radiofrequency energy absorbed over any ten grams of contiguous limb tissue remains within regulatory exposure limits during maximum power transmission. The metric applies to devices worn on or operated against hands, wrists, feet and ankles.
It excludes head and trunk exposures, which follow stricter mass-averaging boundaries.
Exposure Boundary
Physical contact between small form factor radio devices and human extremities presents distinct thermal dissipation conditions compared to torso contact. The regulatory threshold for 10g extremity sar is set at four watts per kilogram in most regulatory jurisdictions. Testing evaluates localized SAR across extremities during worst-case operational modes.
Handheld cellular modules and wrist-mounted telemetry trackers must pass this threshold prior to commercial release.
Evaluation Protocol
Automated probe positioning systems measure localized electric fields inside liquid phantoms shaped to simulate human limbs. Measurements map spatial energy density across a cubic volume before mathematically averaging power dissipation across a contiguous ten-gram tissue mass. System validation requires calibrated E-field probes and verified tissue phantom liquids at specified operating frequencies.
Test software determines peak 10g extremity sar by identifying maximum field strength coordinates and integrating spatial energy across the surrounding tissue volume. Deviations in probe alignment or liquid dielectric properties compromise test accuracy and invalidation occurs if liquid parameters fall outside a five percent tolerance window.
Compliance Margin
Certification reports document maximum scaled absorption levels alongside manufacturing power tolerances. Hardware revisions changing antenna placement or ground plane dimensions alter RF energy distribution and require mandatory re-evaluation. A compliant 10g extremity sar evaluation forms part of the final FCC technical filing package.