EMC Technologies - Introduction to EMC

EN61000-4-3 AND UNIFORM TEST FIELD REQUIREMENTS
THE NEED FOR SEMI-ANECHOIC CHAMBERS

The European EMC standards emerging form CENELEC are the driving force worldwide. As new standards are published and as the existing ones continually evolve, the development and upgrading of EMC test facilities requires large investment in capital equipment and in the human resources necessary to support them. EMC Technologies has recently invested over $900,000 in the upgrade of their Melbourne and Sydney EMC test facilities to allow fully compliant testing to the revised European radiated immunity standards.

The new generic immunity standard EN50082-1:1997 calls up EN61000-4-3 which requires the establishment of a uniform test field over the area occupied by the test sample. This is performed in an anechoic chamber lined with ferrite absorber tiles, which serve to dampen reflections and resonances so that a uniform test field can be established within the chamber. This overcomes the deficiencies of conventional un-lined chambers where reflections and field gradients can cause sudden and often unrepeatable test failures. Testing is performed on products ranging from very large devices such as trucks and mainframe computers, to very small devices such as medical implants and pocket computers. The chamber has large double doors for access by large trucks and equipment. Extractor fans are also fitted for exhaust venting. The semi-anechoic chamber is also ideal for very accurate in-door precompliance “no ambient” radiated emission measurements.

The chambers were constructed to EMC Technologies mechanical and RF design specifications so that they could accommodate the 10 tones of ferrite tiles lining the chamber surfaces. The ferrite tiles are mounted on a dielectric material to enhance the performance of the absorber for frequencies of 26 MHz up the 2000 MHz. In unlined chambers, reflections from the metallic surfaces cause resonances and standing waves which can produce peaks and troughs in the intensity of the test field.	Field gradients of up to 20 to 40 dB are common in un-lined chambers and this can induce sudden failure modes for what may appear to be a very low field at the test sample. Chamber resonances results in poor test repeatability and a high probability of “over testing”. (This may result in the over design of the product). These serious deficiencies are eliminated by the new radiated immunity standard.

High power broadband RF amplifiers are used over the frequency range of 26 MHz to 2000 MHz to drive broadband transmitting antennas at a distance of 3 metres from the device under test. Fully automated tests and calibrations is performed by sophisticated software developed in-house by EMC Technologies. It allows great flexibility in the testing and is fully programmable for all key parameters such as sweep rate, frequency dwell time, modulation and field intensity. Software hooks allow synchronized monitoring and stimulus of the EUT functionality. Interactive functions permit real time changes in both the EMC test software and the EUT parameters. This user access allows rapid logging of all test data for efficient evaluation and analysis of the EUT EMC performance.
Even the very large electronics manufacturers find it difficult to justify the high costs necessary to establish and maintain such a facility. EMC Technologies now provides this valuable testing service to Australian manufacturers wishing to test their products to the new radiated immunity standards or for CE marking purposes. They remain at the forefront of approvals testing in Australia.

Ferrite lined semi-anechoic chamber with 16 point grid for calibration

A 16 point calibration frame is replaced with a table when a calibration is completed. The EUT is subsequently placed upon the table for testing coincident with the calibration plane.

High performance broadband amplifiers and a bilogical antenna allow sweeps from 80MHz to 1000MHz without the need to change antennas.

The area on the floor between the antenna and the equipment under test is also lined with ferrite tiles to minimise variability in the radiating field due to reflections.

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Call any time on: +61 418 566 466

EMC Technologies - Victoria (Head Office)

176 Harrick Road Keilor Park Victoria 3042 Australia
Ph: +61 3 9365 1000 Fax: +61 3 9331 7455

EMC Technologies - New Zealand

47 MacKelvie Street, Grey Lynn, Auckland New Zealand Ph: + 64 93600 862 Fax: + 64 93600 861

EMC Technologies - New South Wales

Unit 3, 87 Station Road, Seven Hills NSW 2147 Australia Ph: + 612 9624 2777 Fax: + 612 9838 4050

EMC Technologies - Queensland

Unit 1 / 15 Success Street, Acacia Ridge 4110 Qld Australia Ph: + 617 3875 2455 Fax: + 617 3875 2466

EN61000-4-3 AND UNIFORM TEST FIELD REQUIREMENTSTHE NEED FOR SEMI-ANECHOIC CHAMBERS

EN61000-4-3 AND UNIFORM TEST FIELD REQUIREMENTS
THE NEED FOR SEMI-ANECHOIC CHAMBERS