Accurate Retrieval of Antenna Patterns in Reflective Environments Via the Test-Zone Field-Compensation Technique

Countless degrees of freedom in the design of antenna test ranges are enabled if the measurement errors caused by the environment can be precisely compensated. Measurements in highly reflective measurement chambers and with broadband feeds or probes are possible since the quality of the test zone is not essential anymore. To create a reflective environment, a metal plate is installed in an anechoic chamber and a base transceiver station antenna is characterized with and without the additional scattering source at a frequency of 2.11 G Hz. To compensate for the undesired signals, the field of the test zone is measured on a spherical surface using a scanning arm. Via a wave expansion of the field and the antenna under test into spherical mode coefficients, the undesired signals are compensated. It is shown that the error of the compensated pattern compared with the undistorted measurements is mainly below -30 dB and that the directivity is retrieved with a difference of only 0.011 dB.