A system includes: a planar antenna array that includes a plurality of right-hand circularly polarized (RHCP) antennas and left-hand circularly polarized (LHCP) antennas in a planar surface or in layers, in which each antenna element includes a spiral plate; a feed network connecting a signal to each of the antennas; and amplifiers dispersed in the feed network configured to provide spatial power combining and beam forming of the signal. A method for detecting concealed objects includes: scanning with a first transmitted signal having a first polarization; receiving reflected signals from the first transmitted signal; scanning with a second transmitted signal having a second polarization different from the first polarization; receiving reflected signals from the second transmitted signal; performing image processing using reflected signals with the first polarization; performing image processing using reflected signals with the second polarization; and combining the image processing from both polarizations to provide enhanced image resolution.