IEC 62209-2: Human Exposure to RF Fields — Specific Absorption Rate (SAR) — Part 2: Handheld and Body-Mounted Devices

IEC 62209-2, published in 2010, specifies the measurement procedures for determining the specific absorption rate (SAR) of wireless communication devices used in close proximity to the human body. This standard specifically addresses devices operated at the head, body, or limbs, covering a frequency range from 30 MHz to 6 GHz. While Part 1 of the series (IEC 62209-1) covers SAR measurement for devices positioned at the ear (phones), Part 2 extends the methodology to body-mounted and handheld devices including smart phones in body-worn configurations, tablets, portable computers with wireless interfaces, wireless gaming controllers, wearable devices, and industrial handheld radios. As wireless device usage patterns have shifted dramatically toward diverse body-contact scenarios, IEC 62209-2 has become an essential tool for regulatory compliance testing across global markets.

SAR Measurement System and Phantom Requirements

The standard requires a measurement system consisting of a dosimetric probe (typically a small isotropic E-field probe with three orthogonal diode-loaded dipoles), a robot or mechanical positioning system with positional accuracy of at least +/- 0.2 mm, and tissue-equivalent liquid (homogeneous head and body simulant liquids with precisely controlled dielectric properties). The phantom — the physical model of the human body — is a critical component. For body-mounted device testing, a flat phantom (rectangular or planar) is specified, simulating the torso or limb with a shell thickness of 2.0 +/- 0.2 mm and tissue-equivalent liquid filling. For head-mounted devices, the standard references the SAM (Specific Anthropomorphic Mannequin) phantom defined in IEC 62209-1.

The tissue-equivalent liquids must be within the following target dielectric parameter ranges for the frequency band under test: relative permittivity (er) of 35-55 and conductivity (s) of 0.8-2.0 S/m for head tissue, and er of 40-60 with s of 0.8-2.5 S/m for body tissue. The liquids must be validated before each test series by measuring the complex permittivity using a dielectric probe kit and vector network analyzer. Deviation from target values must be within +/- 5% for permittivity and +/- 10% for conductivity. The liquid depth must be at least 15 cm to eliminate reflections from the phantom bottom that could perturb the measured SAR distribution.

Measurement Protocol and Uncertainty Analysis

The measurement procedure involves mounting the device-under-test (DUT) precisely at the specified separation distance from the phantom surface using a low-permittivity spacer (typically 2 mm for body-worn devices). The DUT is operated at maximum conducted output power across all applicable wireless technologies and frequency bands. The system performs an area scan at a uniform spacing of typically 10-15 mm to locate the peak SAR region, followed by a finer-resolution zoom scan (approximately 5 mm spacing) around the peak. The zoom scan uses a 3D grid typically extending 30 mm into the phantom to determine the volume-average SAR over 1 g and 10 g of tissue mass. The compliance criterion is defined as 1.6 W/kg for 1 g average (as required by FCC in the US) or 2.0 W/kg for 10 g average (as per ICNIRP guidelines adopted in most of the world including EU, China, Japan, and Australia).

Uncertainty analysis is a fundamental requirement of IEC 62209-2. The standard mandates that the expanded measurement uncertainty (k=2, 95% confidence level) be evaluated and reported for each SAR measurement system. The combined uncertainty budget must include contributions from probe calibration (typically 5-7%), probe positioning (2-4%), liquid dielectric property tolerances (3-5%), measurement system linearity and isotropy (3-5%), DUT positioning repeatability (3-6%), and phantom shell effects (2-4%). The total expanded uncertainty should be below 25% for a valid measurement, with state-of-the-art systems achieving 18-22%. If the measured SAR exceeds the regulatory limit when accounting for measurement uncertainty, the device fails the compliance assessment.

Engineering Design Insights for RF Exposure Compliance

From a product design perspective, SAR compliance involves multiple interacting engineering disciplines. Antenna design choices fundamentally determine SAR performance: planar inverted-F antennas (PIFA), loop antennas, and patch antennas each exhibit distinct near-field coupling characteristics with the human body. For body-worn devices, the antenna should ideally be positioned on the side of the device facing away from the body, a design strategy known as “body-opposite antenna placement.” The ground plane size and shape also significantly affect SAR — a larger ground plane can reduce SAR by distributing the RF currents over a wider area, but this must be balanced against mechanical constraints and industrial design requirements.

Power management strategies are increasingly important for SAR compliance in multi-radio devices. The standard allows simultaneous transmission SAR evaluation for devices operating multiple radios simultaneously (e.g., LTE + Wi-Fi + Bluetooth). The combined SAR must be evaluated per the multi-transmitter assessment procedures, with the total SAR not exceeding the regulatory limit. Manufacturers implement SAR-based power back-off algorithms that detect body proximity (using capacitive or infrared sensors) and reduce transmitter power accordingly, a technique now widely used in modern smartphones to simultaneously maintain high radiated performance in free space while ensuring SAR compliance in body-contact scenarios.

Finally, the test lab environment must maintain stringent quality controls. System validation checks using reference dipoles must be performed at least every 12 months (preferably every 6 months for high-throughput laboratories), and the system must demonstrate that the measured SAR at the reference dipole calibration point is within +/- 10% of the certified value. Daily system checks (less comprehensive than full validation but sufficient to verify drift-free operation) are also recommended to ensure day-to-day measurement consistency.