Using the 'Test Wire' Method as an Alternative to the CISPR 12 Full Vehicle Measurement Method

This paper investigates the use of the ’Test Wire Method’ in an attempt to reduce 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. A ’Test Wire’ system was originally suggested as method of performing in-situ radiated emissions measurements on physically large electrical machines. The current CISPR 12 test method potentially under-estimates the emissions levels significantly for a representative body-shell model, the results obtained during measurements of a scale model, using the Test Wire Method are discussed and compared to the standard CISPR 12 methods. The initial findings suggest that using the Test Wire Method may offer an improvement (in the region of 4dB) in the error recorded in determining the maximum amplitude of the emissions signature of the vehicle, within the measurement environment being utilised. It is hoped that by the use of an increased number of configurations of the measurement model, further improvements may be recorded. As this paper describes work in progress the measurement results will be validated using simulations of an EM scale model as the next part of this program.