Shielding Effectiveness Test Following the Standard MIL-STD-285

The Standard MIL-STD-285 (currently replaced by IEEE-299) is called coplanar setup and it describes uniform procedures for measuring shielding effectiveness (SE) for enclosures at frequencies from 9 kHz to 18 GHz (extendable down to 50 Hz and up to 100 GHz), although the smallest linear dimension of the enclosure is assumed to be at least 2 m; the selection of 2 m as the smallest linear dimension was originally based upon being able to fit a typical bicone-style antenna inside an enclosure to perform plane-wave testing down to the range from 30 to 50 MHz.

The standard does not give any limits for pass/fail, leaving to the owner of the shielding enclosure to provide these limits. In addition, although the standard suggests a range of test frequencies that can provide confidence in the effectiveness of the shield, it is clearly stated that the actual test frequencies must be chosen according to a test plan approved by the shield owner, the tester, and the shielding provider/vendor.

The measurement range in this method is divided into three subranges and in each subregion, some subgroups of testing frequencies are suggested:

  1. Low-frequency range: from 9 kHz (50 Hz) to 20 MHz (a single frequency is suggested within 9-16 kHz, 140-160 kHz, and 14-16 MHz) where the SE is defined in terms of magnetic-field performance.
  2. Resonant range: from 20 to 300 MHz, where the SE is expressed in terms of either electric field or power.
  3. High-frequency range: from 300 MHz to 18 GHz (100 GHz) (a single frequency is suggested within 300-600 MHz, 600-1000 MHz, 1-2 GHz, 2-4 GHz, 4-8 GHz, and 8-18 GHz) where the shielding performance of the enclosure is expressed in power terms.

EMCTEST Technologies is a leading test laboratory in Italy and Europe for electromagnetic shielding effectiveness testing. Thanks to advanced instrumentation and extensive experience in the field, we perform measurements from 10 kHz to 110 GHz on materials and devices intended for industrial, telecommunications, medical, military, automotive, railway, marine, aerospace, scientific, governmental, and civil applications.

Typical Test Frequencies

  • Low frequency: 10 kHz, 100 kHz, 500 kHz, 1 MHz
  • Mid frequency: 10 MHz, 30 MHz, 100 MHz, 433 MHz, 700 MHz, 800 MHz, 900 MHz
  • High frequency (RF and microwave): 1 GHz, 1.5 GHz, 2.4 GHz (ISM band), 3 GHz, 5 GHz, 5.8 GHz, 6 GHz, 10 GHz
  • Very high frequency: 17 GHz, 18 GHz, 24 GHz (ISM, Industrial, Scientific, and Medical bands), 26.5 GHz, 30 GHz, 35 GHz, 40 GHz, 50 GHz, 60 GHz (wireless communication and radar applications)
  • Millimeter wave: 75 GHz, 77 GHz (automotive radar systems), 94 GHz, 100 GHz, 110 GHz

Our test laboratory is equipped to perform shielding effectiveness measurements up to 110 GHz.

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