Effects of RF absorbers on measurements of small antennas in small anechoic chambers

In this work, the influence of resistive absorbers in the vicinity of small antennas was investigated, in order to define a lower limit for the size o f a small anechoic chamber for antenna calibration and radiation pattern me asurements, with respect to the distance between the antenna under test (AU T) and the RIP absorbers lining the walls. Furthermore, the influence of a relatively narrow transmission channel, formed by the absorbers on the side walls between the measurement antenna and the AUT was investigated. It was found by measurements that absorbers with the length of 610 mm do not have a measurable effect on the radiation characteristics of a small antenna at around 1.8 GHz, as long as they are kept more than 100 nun from the AUT, a nd the transmission channel formed by the absorbers between the antennas is wider than 100 nun.