An investigation into the errors in the CISPR 12 full vehicle radiated emissions measurements due to vehicle directivity

This paper investigates the errors in the current CISPR 12 full vehicle radiated emissions tests due to the vehicle directivity. CISPR 12 measurements are performed using a fixed geometrical configuration, this method is different to many other radiated emissions standards where receive antenna height scan and device under test azimuth rotation through 360 degrees is employed in an attempt to maximise the emissions recorded. Numerical results of a simplified vehicle body shell are discussed. Data recorded between 100 MHz and 500 MHz shows that the current CISPR 12 test method potentially under-estimates the emissions levels by up to 17dB for a representative body-shell model, suggesting that the existing version of CISPR 12 may require further development in order to more closely determine the maximum amplitude of the emissions signature of the vehicle, within the measurement environment being utilised.