A Low-Profile Shared-Aperture Dual-Band Broadband Antenna Array for SAR Applications

A low-profile shared-aperture dual-band broadband antenna array for potential applications in synthetic aperture radars (SARs) is presented. The proposed antenna array operates in L- and C-bands with a frequency ratio of 1:3.3. The C-band elements are selected as stacked microstrip dipoles, which employ stepped gradient structure to broaden the bandwidth. The L-band elements are selected as perforated patches to enable the placement of C-band elements within them. Both the L- and C-band elements are fed by proximity coupling. To reduce the antenna profile, both of the two feed networks are placed above the ground plane. The measured results agree well with the simulations, showing a wide impedance bandwidth of 6.54% and 21.11% at L- and C-bands, respectively. The antenna array also exhibits good radiation performance with the high cross-polarization discrimination at each band. Compared with the conventional dual-band shared-aperture SAR antenna, the proposed antenna array has a significant reduction in the profile, which is 5.7 mm, and achieves a wide bandwidth in both of the two operation bands.