THE GROUNDPLANE RESONANCE: PROBLEMS WITH RADIATED EMISSIONS MEASUREMENTS BELOW 30 MHz
Dr Luke Turnbull
Abstract: This paper describes reproducibility problems when making radiated emissions measurements of automotive, aerospace and military components in the frequency range 10 MHz - 30 MHz. The problems are caused by resonances that are introduced by the test setup. Unfortunately, the behaviour was understood over 20 years ago, but the mitigating changes to the test setup have not become widespread, partly because a pragmatic chamber verification method has not yet been devised.
Two novel chamber verification methods are described. It is shown how these can be used to improve the test setup such that resonances are reduced and therefore test reproducibility greatly improved.
Recommendations are made to standardisation bodies to incorporate these verification methods and to specifically allow changes to the test setup that will reduce resonances.
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