Circularly Polarized Corporate-Feed Beam-Scanning Array With Low Profile

A low-cost low-profile circularly polarized (CP) corporate-feed beam-scanning array is presented. As the main part of the feed network, we found that the sidewall reflection of the parallel plate waveguide (PPW) is the major reason for the deterioration of the beam-scanning performance at large angles. Therefore, a hybrid feed network composed of PPW and substrate integrated waveguide (SIW) is proposed. Mechanical beam scanning is realized by a planar parabolic reflector-based line source generator (LSG). To expand the beamscanning range, an SIW delay line-based phase compensation structure is introduced after theoretically analyzing the phase deviation generated by the LSG. The CP radiation is realized by improved CP antenna elements with a wide 3 dB axial ratio (AR) beamwidth. These CP antenna elements are fed by a corporatefed network to avoid the frequency-dependent squint beam. A K-band prototype of an 8 x 14 array is fabricated and measured to verify the design. According to the measured results, the beamscanning range of 0 degrees-51 degrees in elevation with the peak gain of 22.3 dBi is realized. The gain variation and ARs in this scanning range are less than 2.9 and 2.5 dB, respectively.