edVirtus Reference

IEC/IEEE 62704 Series—Determining the Peak Spatial-Average Specific Absorption Rate (SAR) in the Human Body from Wireless Communications Devices, 30 MHz to 6 GHz

Preview: Learn more about the IEC/IEEE 62704 series and its computational procedures for determining SAR using FDTD and FEM.

The IEC/IEEE 62704 series specifies computational procedures for determining specific absorption rate (SAR) in human models exposed to fields from wireless communication devices. It establishes reproducible uses of the finite-difference time-domain (FDTD) and finite-element (FEM) methods, including model requirements, numerical verification, physical validation, uncertainty assessment, spatial averaging, and reporting.

The publications are IEC/IEEE Dual Logo standards prepared through IEC Technical Committee 106, Methods for the Assessment of Electric, Magnetic and Electromagnetic Fields Associated with Human Exposure, in cooperation with the IEEE International Committee on Electromagnetic Safety. They provide assessment methods; the applicable SAR limits and regulatory decision rules are supplied by exposure standards and national authorities.

Series purpose and structure

The series provides a common technical foundation for using full-wave computation as evidence in RF product and exposure assessment. Part 1 gives general FDTD requirements. Parts 2 and 3 apply FDTD to vehicle-mounted antennas and mobile phones respectively. Part 4 gives general FEM requirements. The parts are complementary rather than interchangeable.

A series-level reference is useful because the same principles recur across the parts: define the device and exposure configuration; construct suitable computational and human models; solve Maxwell's equations; calculate SAR; evaluate the required spatial average; verify the software implementation; validate the physical model; quantify uncertainty; and report enough information for an independent technical review.

Purpose and scope

The overall title identifies wireless communication devices from 30 MHz to 6 GHz, but the detailed scope depends on the part used. Parts 1, 3, and 4 address peak spatial-average SAR over that general frequency range. Part 2 currently applies its vehicle-mounted-antenna procedures over 30 MHz to 1 GHz, notwithstanding the broader series title.

The standards are concerned principally with numerical determination of SAR within phantoms or anatomical models. They are not general-purpose site-survey standards and do not replace external-field measurements where those measurements answer the compliance question directly. Their value is greatest when internal energy absorption must be calculated or when physical scanning is impractical.

The required result is obtained for a defined source, geometry, operating condition, body model, and averaging rule. A calculation is therefore conditional on its inputs. A technically correct solver can still produce an irrelevant compliance result if the modeled power, antenna, separation, orientation, posture, material properties, or exposure scenario do not represent the case under assessment.

The series does not set health-based exposure limits. Calculated SAR must be compared with the applicable basic restriction, averaging mass, exposure category, time-averaging requirement, uncertainty treatment, and decision rule specified by the relevant authority. Jurisdiction-specific product-authorization procedures can add configurations or acceptance criteria.

Part 1—General requirements for FDTD calculations

IEC/IEEE 62704-1:2017 defines the general methodology for applying FDTD to determine peak spatial-average SAR from wireless communication devices with known uncertainty. It addresses device-model validation, software verification, numerical requirements, evaluation of SAR in a cubical averaging volume, and the information needed to demonstrate that the implemented calculation is fit for its intended purpose.

Part 1 is the foundation for FDTD applications that are not fully specified by a product-specific part. It describes how discretization, boundaries, sources, material properties, convergence, and post-processing affect the result. It should be used with a more specific procedure where one applies, because the specific part supplies the standardized geometry, configurations, or benchmarks for that application.

Part 2—Vehicle-mounted antennas

IEC/IEEE 62704-2:2017, incorporating Amendment 1:2025, applies FDTD to exposure from vehicle-mounted antennas. It specifies a test vehicle, standardized anatomical models, antenna locations, operating configurations, exposure conditions, and benchmark data representative of occupants or people near high-power mobile-radio installations. It addresses both peak spatial-average and whole-body-average SAR.

Although the series title extends to 6 GHz, the present Part 2 procedure covers 30 MHz to 1 GHz. This includes many land-mobile and public-safety radio applications. The amendment updates the standard without changing its basic role: it remains the application-specific computational route for evaluating coupling between vehicle-mounted antennas, the vehicle structure, and standardized human models.

Part 3—Mobile phones

IEC/IEEE 62704-3:2017 specifies FDTD requirements for calculating peak spatial-average SAR from mobile phones in standardized head and body phantoms. It is particularly relevant to design and pre-compliance work, where a validated numerical phone model can be assessed in prescribed positions before or alongside laboratory measurement.

Part 3 provides benchmark phone models and results, modeling guidance, meshing requirements, test positions, validation procedures, uncertainty considerations, and limitations. It does not allow an arbitrary handset model or convenient orientation to stand in for the required configuration. The numerical device and phantom must meet the prescribed representation and validation requirements.

Part 4—General requirements for FEM calculations

IEC/IEEE 62704-4:2020 describes the concepts, techniques, and limitations of FEM for calculating peak spatial-average SAR in phantoms or anatomical models. It specifies model requirements, verification, validation, uncertainty assessment, and benchmark data, and it provides guidance on representing wireless communication devices over 30 MHz to 6 GHz.

Part 4 is the FEM counterpart to the general FDTD foundation in Part 1, but the numerical methods are not identical. FEM's flexible elements and local refinement can represent curved boundaries, thin structures, and complex source geometry efficiently. The assessor must still demonstrate mesh adequacy, solver convergence, valid boundaries, and appropriate post-processing.

FDTD and FEM

FDTD divides the computational domain into cells and advances electric and magnetic fields through discrete time steps. It is well suited to broadband excitation and voxel-based anatomical models. Accuracy depends on spatial resolution, time-step stability, material assignment, source representation, absorbing boundaries, and the treatment of curved or fine structures within the grid.

FEM divides the domain into interconnected elements and commonly solves the fields at individual frequencies. Local mesh refinement and higher-order elements can efficiently represent irregular geometry, but accuracy depends on element quality, basis functions, domain truncation, material data, and solver convergence. Neither method is inherently superior for every device or exposure problem.

Device and human models

A device model must reproduce the electromagnetic behavior relevant to exposure. Important inputs include antenna geometry and currents, feed or port definition, conducted or accepted power, frequency, housing and internal structures, nearby accessories, separation, orientation, and operating modes. Simplification is acceptable only when its effect is understood, justified, and included in validation or uncertainty.

Human representations range from standardized homogeneous phantoms to anatomically detailed tissue models. Geometry, posture, body size, tissue boundaries, dielectric properties, and source position influence coupling and absorption. The selected model must suit the applicable part and assessment purpose; a more anatomically detailed model is not automatically more accurate if its material or positioning inputs are poorly controlled.

Peak spatial-average SAR

SAR is the rate of RF energy absorption per unit mass and is expressed in watts per kilogram. Local absorption near a wireless device is highly nonuniform, so the compliance quantity is generally the greatest spatial average within a specified tissue mass. The numerical procedure must locate the relevant maximum and evaluate the prescribed averaging volume without truncation or inappropriate smoothing.

Mesh values are not themselves the final compliance result. Electric fields and material properties are used to calculate local SAR, after which a defined algorithm forms the spatial average. Grid resolution, mass assignment, tissue boundaries, interpolation, averaging-volume shape, and handling of air or excluded tissues can all affect the reported peak value.

Verification and validation

Verification establishes that the numerical equations and required post-processing have been implemented and solved correctly. The series uses analytical comparisons, standardized benchmarks, grid or mesh refinement, convergence checks, energy balance, and reference models to reveal programming, discretization, boundary, or averaging errors. A plausible field image is not sufficient verification.

Validation establishes that the computational model represents the physical device and exposure configuration adequately. It can involve comparison with measured input characteristics, fields, or SAR; standardized reference antennas or models; and sensitivity to positioning and materials. Verification cannot compensate for an invalid device model, and experimental agreement at one point does not validate every configuration.

Uncertainty and reporting

Computational uncertainty can arise from source power, geometry, position, material properties, tissue data, mesh resolution, numerical dispersion, boundary conditions, solver convergence, device simplification, averaging, and validation measurements. Contributions should be evaluated on a consistent basis, combined appropriately, and related to the final SAR result and compliance decision.

A reproducible report identifies the applicable series part and edition, software and version, solver settings, source and operating state, geometry, human model, material data, mesh, boundaries, convergence studies, verification benchmarks, validation evidence, SAR averaging procedure, uncertainty budget, results, limitations, and any conservative assumptions. Controlled model and input files are part of the technical evidence.

Relationship to measurement and other standards

Computational and measurement methods are complementary. IEC/IEEE 62209-1528 provides measurement procedures for SAR from hand-held and body-mounted devices over 4 MHz to 10 GHz. The IEC/IEEE 62704 series provides computational SAR procedures principally through 6 GHz. A product program can use calculation for design and configuration screening while retaining the measurement or computational evidence required by the authority.

The applicable exposure-limit standard supplies the basic restriction. Examples include the ICNIRP Guidelines, IEEE Std C95.1, and national standards derived from them. Exceeding or meeting a numerical value has regulatory meaning only when the correct limit, averaging mass, operating condition, uncertainty treatment, and decision rule have been applied.

For close-proximity devices above 6 GHz, the IEC/IEEE 63195 series provides measurement and computational procedures for incident power density. The choice among SAR, absorbed or incident power density, measurement, and computation depends on frequency, device configuration, applicable framework, and product-authorization requirements. Overlap regions must be handled as the governing regime specifies.

Edition and amendment status

As of August 2026, the published series comprises IEC/IEEE 62704-1:2017, IEC/IEEE 62704-2:2017 with Amendment 1:2025, IEC/IEEE 62704-3:2017, and IEC/IEEE 62704-4:2020. IEC Technical Committee 106 has reported ongoing development of second editions. Users should confirm the current catalogue status and the edition adopted by the relevant authority before beginning an assessment.

Practical significance

The IEC/IEEE 62704 series turns computational RF dosimetry into a controlled assessment method rather than an informal simulation. It is important to wireless-device manufacturers, antenna and product designers, accredited laboratories, regulators, and technical assessors who need defensible internal-absorption results for configurations that are difficult to measure directly.

Its central discipline is traceability from the physical question to the compliance result. A credible assessment connects a defined source and exposure scenario with a suitable human model, verified numerical method, validated device representation, correct spatial averaging, quantified uncertainty, and complete report. That chain is what allows computed SAR to function as reliable evidence rather than merely as software output.