A low cost conversion of semi-anechoic chamber to fully-anechoic chamber for RF antenna measurements

The commonly use of semi-anechoic chambers (SAC) is for electromagnetic interference emission (EMI) measurements. This paper suggests a simple technique to extend the EMI chamber capability to a low-cost fully anechoic chamber (FAC) to characterize the antenna performance. The dimensions of the absorbing cones placed o the reflecting ground surface are based on the Fresnel´s zone concept. The receiving antenna operating from 300 MHz to 1 GHz is best located at the corner of the chamber. With the available 2´ absorbing cones, the maximum distance between transmitting and receiving antenna of 4.5 meters, and the far-field criteria, the applicable antenna pattern measurement at 300 MHz requires only about 80% of the first Fresnel´s zone cone coverage. Within the 0.5×0.5 m² area, at 60 MHz the worst case field uniformity is about 1.4 dB.