Meaning
Portable radio devices operated in close proximity to the human torso require evaluation of RF exposure limits. Manufacturers of body-worn transmitters must ensure that the Specific Absorption Rate (SAR) does not exceed limits specified by safety standards. Measurements are performed using a tissue-equivalent phantom.
Compliance Procedure
Standardized testing ensures that the equipment complies with regional radiation limits before market release. Devices such as body-worn transmitters undergo evaluation at a specific distance from the phantom, representing the worst-case scenario. This distance is maintained by a dedicated spacer during testing.
Testing Configuration
Proper alignment against the tissue-simulating model is necessary to capture maximum RF absorption. Testing of body-worn transmitters often involves a flat phantom that represents the human torso. Sensor arrays measure the electric fields within the tissue-simulating liquid to calculate the peak absorption.
Hardware Integration
Designers must manage both antenna design and housing materials to control radiation directed toward the user. Antennas inside body-worn transmitters are positioned to minimize energy deposition in the direction of the body. Dynamic power reduction algorithms are frequently implemented in the firmware to lower the conducted transmit power during close contact events.
Proximity sensors detect the presence of the human body and trigger these mitigation mechanisms to achieve compliance without compromising the wireless link budget during normal operation.
