Low-Profile Inverted Ridged-Waveguide Slot Array with Asymmetric Feed for 2D Wide-Angle Scanning Spaceborne SAR

A low-profile inverted ridged-waveguide slot array antenna with asymmetric feed is proposed for two-dimensional (2D) wide-angle scanning spaceborne synthetic aperture radar (SAR) applications. The inverted ridge and asymmetric feed structure enables broad-wall radiating slots without lateral offset, achieving an ultra-low profile of 0.28λ0, significantly lower than typical ridged-waveguide slot arrays for 2D wide-angle scanning applications, while supporting a compact inter-element decoupling configuration. H-shaped slots are further introduced to enhance the structural robustness of large-scale lightweight phased arrays without radiation performance degradation. The fabricated antenna element attains a wide relative bandwidth of 23.16% in the X-band. In array operation, the active voltage standing wave ratio (VSWR) remains below 2.0, and the phased array achieves 2D beam scanning coverage of ±55° in elevation and ±15° in azimuth.