ASTM D4935-18 PDF

Full title and description

ASTM D4935-18 — Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials. This method provides a standardized procedure to measure shielding effectiveness (SE) of flat/planar materials under normal incidence, far-field plane-wave conditions and includes guidance on measurement uncertainty, calibration and separation of reflection and absorption contributions to SE.

Abstract

ASTM D4935-18 specifies a TEM-style transmission line test fixture and measurement procedure for quantifying the electromagnetic shielding effectiveness of planar materials across a defined radio-frequency band. The procedure yields far-field SE values from which approximate near-field SE values can be derived for certain magnetic (H) source cases; it measures net SE due to both reflection and absorption and provides appendices addressing uncertainty analysis and example calculation/code. The method is intended for material-level characterization, not for cables or connectors.

General information

• Status: Active standard (current designation D4935-18).
• Publication date: May 15, 2018.
• Publisher: ASTM International.
• ICS / categories: 33.100 Electromagnetic compatibility (EMC).
• Edition / version: D4935-18 (revision of D4935-10).
• Number of pages: 11 (includes normative text and appendices).

Scope

This test method provides a procedure for measuring electromagnetic shielding effectiveness (SE) of planar materials for a plane, far-field electromagnetic wave under normal incidence. The published valid frequency range for the method is approximately 30 MHz to 1.5 GHz. The procedure is not applicable to cables or connectors. Units are SI. The standard also notes practical limits driven by displacement currents at low frequency and overmoding at higher frequencies for the specified specimen holder.

Key topics and requirements

• Measurement objective: determine SE (dB) of planar specimens under far-field, normal-incidence plane-wave conditions.
• Frequency range: nominally 30 MHz to 1.5 GHz (select discrete frequencies within this band as appropriate for the material under test).
• Test fixture: TEM/transmission-line style specimen holder and ports sized to avoid overmoding across the band of interest.
• Instrumentation: vector network analyzer (VNA) or equivalent, calibrated bidirectional coupler where separation of reflected and absorbed power is required.
• Data reduction: calculation of net SE (reflection + absorption), optional derivation of approximate near-field SE for electrically thin materials and H-field sources.
• Quality control: calibration, uncertainty analysis (Appendix X1) and example calculation/code (Appendix X2) provided to help quantify measurement uncertainty and reproducibility.
• Limitations: not intended for testing cables/connectors or for characterizing non‑planar structures; edge diffraction and holder size impose practical frequency limits.

Typical use and users

Used by EMC test laboratories, materials manufacturers, R&D teams and product designers to characterize conductive coatings, shielding foils, metallized textiles, gasket and EMI shielding materials, and to compare materials for enclosure design. Typical sectors include consumer electronics, automotive, aerospace, military/defense, medical devices and any industry requiring EMI mitigation at material level prior to system integration.

Related standards

Documents commonly referenced alongside or used for complementary shielding measurements include the predecessor ASTM D4935-10, IEEE 299 (shielding effectiveness of enclosures and rooms), MIL-STD-285 (attenuation measurements for enclosures), MIL-STD-461 (EMC requirements for equipment/subsystems) and other national/international EMC and shielding test methods. Alternative or complementary material-level methods (and enclosure/room methods) may be selected depending on frequency range, specimen geometry and application.

Keywords

electromagnetic shielding effectiveness; SE; planar materials; TEM cell; transmission line; far-field plane wave; shielding measurement; bidirectional coupler; VNA; 30 MHz–1.5 GHz; ASTM D4935-18.

FAQ

Q: What is this standard?

A: ASTM D4935-18 is a standardized test method that specifies how to measure the electromagnetic shielding effectiveness (SE) of planar (flat) materials using a TEM/transmission-line based test fixture and far-field, normal-incidence plane-wave conditions.

Q: What does it cover?

A: It covers specimen preparation and mounting in a specified holder, measurement procedures (typically using a VNA), calculation of net SE (accounting for reflection and absorption), and includes appendices for uncertainty analysis and example code. The method is valid over about 30 MHz to 1.5 GHz and is not intended for cables or connectors.

Q: Who typically uses it?

A: EMC/EMI test labs, materials manufacturers, R&D and design engineers in electronics, automotive, aerospace, medical and defense industries use this method to quantify and compare shielding performance of coatings, foils, fabrics, gaskets and other planar shielding products prior to system-level verification.

Q: Is it current or superseded?

A: The D4935-18 designation is the active/revision published in 2018 (revision of D4935-10). Users should check for any later amendments or revisions from ASTM International before use; as published, D4935-18 is the current ASTM version from May 15, 2018.

Q: Is it part of a series?

A: D4935 is a standalone ASTM test method addressing planar-material SE. It is often used in concert with other EMC and shielding standards (e.g., IEEE 299, MIL-STD-285/461 and other IEC/EN EMC documents) depending on whether material-level, enclosure-level, or system-level characterization is needed.

Q: What are the key keywords?

A: Electromagnetic shielding effectiveness, SE, shielding measurement, planar materials, TEM/transmission line, VNA, bidirectional coupler, far-field, 30 MHz–1.5 GHz, ASTM D4935-18.