Evaluation of chamber effects on antenna efficiency measurements using non-reference antenna methods in two reverberation chambers

In this study, the evaluation of chamber effects on antenna efficiency measurements using non-reference antenna (NRA) methods is presented. Two reverberation chambers have been employed and they differ in dimensions and paddle stirrer configurations, therefore the corresponding electrical characteristics such as quality factors, decay constants, and enhanced backscatter coefficients are envisaged to be different. However, it is found that these differences have little influence on the efficiency measurement of antennas-under-test (AUTs). The AUTs used for this study were a directional antenna and an omnidirectional antenna. The discrepancy in the efficiency of the two antennas measured between the two chambers is < 10% within their operational frequency bands. These results demonstrate that the NRA measurement techniques are robust. Further investigation shows that the directional antenna is slightly more prone to polarisation mismatch than the omnidirectional antenna is. Therefore, polarisation stirring should be implemented when using the NRA methods for antenna efficiency measurement especially for directional antennas.