Meaning
Portable communication hardware held in the human hand must comply with limits for localized RF exposure. During typical operations, handheld terminals emit electromagnetic radiation that must be measured to guarantee user safety.
Ergonomic Positioning
Devices used against the ear or in the palm are positioned differently than those worn on the waist. For handheld terminals, the specific absorption of energy is measured at the hand and wrist. These positions have higher exposure limits than the head or trunk, allowing different maximum power levels.
Testing Setup
Laboratories simulate actual usage by using specialized phantom molds. For testing handheld terminals, a flat phantom or a hand-shaped model filled with simulated tissue is used. Robotic arms scan the probe within the simulated tissue to map the RF energy distribution.
Power Mitigation
RF designers use diverse techniques to maintain low energy absorption while ensuring robust signal strength. In many handheld terminals, proximity sensors detect when a hand is clutching the device housing. Upon detection, the firmware triggers a dynamic reduction in the output power of the active transmitter.
This power back-off ensures the device complies with the localized limits without reducing the wireless range when the device is sitting on a desk or mounted in a vehicle.
