Full duplex communication is able to enhance the spectrum efficiency of wireless channels, one important step of which is the passive suppression technology. To improve the performance of the passive suppression, we have studied different antenna configuration modes, which are based on the electromagnetic interference theory. Making full use of the fading characteristic of antennas, we figure out an effective layout mode to obtain the maximum passive suppression. The measurement results reveal that the average passive self-interference suppression can achieve 52.6 dB. The tests were conducted under various conditions and their combinations, i.e., (a) modulation, (b) polarization, (c) distance, and (d) laying. Test results show that with the help of digital suppression, the total suppression performance can be more than 90dB, which is able to meet the requirements of full duplex communications.