Return loss reduction techniques for an ultra wide bandwidth phased array antenna in V/UHF band

V/UHF indoor Radar Cross Section (RCS) measurements can still be performed when the anechoic chamber dimensions are not large enough compared to the wavelength and the wall absorbing material performances are relatively low. The main issue is that regular transmitting horns have large aperture angles. These radiation patterns do not eliminate the multi-path signals to and from the target after a reflection on the chamber walls. In order to drastically reduce unwanted signals from the chamber, a dual polarization ultra wide bandwidth (120 MHz-1875 MHz) phased array antenna has been designed and developed in 2004. The optimization consisted in lowering the phased array side-lobes in the angular direction of the chamber walls. Clutter signals from these walls were reduced by 40 dB. Among the received signals from the chamber, the return loss of the phased array antenna is now the most significant. After a brief presentation of CAMELIA indoor RCS measurement facility, the phased array antenna is detailed. Then a return loss reduction experimental study for this large phased array antenna is presented. The technical solutions are described and the measured return loss reduction performances are discussed.