Design and verification of synchronization antenna for space-borne interferometric SAR systems

The design of a dual circularly polarized antenna has been proposed to accommodate the requirement of synchronization for space-borne interferometric SAR systems. A metallic septum has been employed in a square horn antenna for achieving circular polarization. Moreover, circular-shaped choke corrugations have been integrated with the waveguide to realize symmetrical radiation patterns. In addition, a novel near-field test method has been presented for accurately obtaining the amplitude and phase patterns of the wide beamwidth synchronization antenna. In contrast with traditional near-field test, the presented measurement mechanism requires larger scanning aperture and smaller sampling interval to achieve high accuracy of the phase pattern. To validate the design of the circularly polarized synchronization antenna and the effectiveness of the test approach, a prototype has been fabricated and evaluated. The obtained results show that the proposed circularly polarized antenna has good impedance matching with VSWR ≤ 1.5 across the operating frequency band and axial ratio ≤ 2 over wide beamwidth. In addition, the phase variation versus angle is less than 2 deg/deg from -70° to +70°, which is significant for synchronization link of two satellites.