Simultaneous Transmit SAR Evaluation Thresholds in Portable Radio Systems
Simultaneous SAR evaluations require summing standalone SAR or estimated values to prove combined exposure remains below regulatory limits.
1-G SAR
Meaning
Electromagnetic energy absorption metrics quantify the rate at which radio frequency power is deposited in a specific volume of biological tissue. Standardized test protocols employ a 1-g SAR measurement to evaluate localized exposure in the United States and other regions following Federal Communications Commission guidelines. This evaluation focuses on the peak spatial-average power delivered to any single gram of continuous tissue shaped as a cube.
The assessment boundary ceases to apply when the radiating source is positioned far enough from the body to qualify for low-power exclusion limits.
Spatial Distribution
High resolution spatial scans locate the precise area of maximum energy deposition within the simulated head or body tissue during device operation. Field probes measure the electric field strength along three axes to determine the peak distribution. This local focus ensures that concentrated hot spots from close-proximity transmitters are accurately identified.
Regulatory Threshold
Safety limits for localized exposure restrict the maximum allowable value to avoid tissue heating. In the fcc regulatory framework, the limit for a 1-g SAR value is set at 1.6 watts per kilogram for the general population. Testing laboratories execute these evaluations with the device operating at its maximum rated output power across all supported frequency channels.
If the measured value exceeds this threshold, the hardware cannot be certified for commercial distribution in that market.
Hardware Integration
System designers mitigate high exposure values by optimizing antenna placement and selecting appropriate chassis materials. Implementing proximity sensors allows the modem to dynamically reduce transmit power when the device is close to a user. This power reduction lowers the 1-g SAR output without degrading the link quality during normal operation.
Device certification documents must contain detailed test logs showing compliance under all simulated usage scenarios.