Design of a broadband microwave absorber from wideband receiving antenna array

In some extent, microwave absorbers and receiving antennas have some similarities, for both of them aim at receiving the ambient electromagnetic wave around. The essential difference between them is that the receiving antenna must transmit the EM wave to the loading system, but the microwave absorber just need to dissipate them. In this work, we studied a novel broadband microwave absorber, which is achieved from a wideband folded-dipole antenna array backed through a quarter-wavelength spacer by a metal ground. By studying the impedance locus of the folded dipole array on Smith chart, the authors first obtained a wideband folded-dipole array antenna, and then changed it to an absorber by replacing the excitations with lump resistors. Both simulation and measurement results show that the folded-dipole array-based microwave absorber can achieve a wide bandwidth of 100% at the normal incident waves as in mode of antenna array, while the center frequency is at 5.5GHz. Meanwhile, the -10dB bandwidth of the absorber can still be over 90% at an oblique incident waves of 30 degrees.