Navigating Modular Approvals and Host Integrator Responsibilities
Modular radio approvals cover baseline intentional radiation but transfer host level unintentional emissions, SAR exposure, and final assembly compliance to the integrator.
Localized Body SAR
Meaning
Localized rate of energy absorption quantifies the RF power deposited by a wireless device in a specific, small volume of human body tissue. Measuring localized body SAR is required for devices that are used within close proximity of the user, such as wearable sensors or mobile handsets. This metric ensures that the localized heating of tissue does not exceed safe regulatory levels.
Exposure Limit
Regulatory agencies set different limits for the head, limbs, and torso, with the localized torso measurements being the most common for body-worn equipment. The test simulates the worst-case scenario where the device transmits at its maximum power level. If the measured absorption exceeds the limit, the device cannot be certified for sale.
Testing Method
The device is placed against a phantom representing human tissue while a robotic probe scans the electric field within the liquid. This provides a direct measure of the energy absorbed.
Product Design
To comply with these limits, designers can decrease the transmitter power or optimize the antenna radiation pattern away from the body. Using materials with lower dielectric constants for the housing can also affect the energy distribution. These changes must be verified through a series of test iterations before the final design is locked.