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In this article, a 1 × 4 wideband, dual-polarized patch antenna array fed by a novel, differentially fed structure is proposed. The differentially fed structure of the antenna was realized by a parallel line structure that was printed on a PCB and connected with the inner and outer conductors of a coaxial cable. This method elaborately solved the problem of the narrow bandwidth of conventional microstrip differential feeding. By using a relatively thick air substrate (thickness = 0.19 λ0), stacked patches, a coupling feeding structure, and a differential feeding structure with the novel design, the element of the patch antenna array introduced below operated from 0.415 GHz to 0.707 GHz (achieving the 52.0% bandwidth) with a VSWR < 2.0, yielding a high port isolation less than −28 dB. For the array, an active VSWR less than 2.0 was also obtained with a port isolation of less than −25 dB, ranging from 0.405 GHz to 0.696 GHz. In the desired bandwidth, the array had an azimuth 3 dB beamwidth of about 19° for both horizontal polarization and vertical polarization. The antenna array also had good performance in scanning (stable gain and 3 dB beamwidth) and circular polarization (a 3 dB axial ratio bandwidth better than 54.5%). [ABSTRACT FROM AUTHOR]

Range ambiguities severely degrade the performance of the synthetic aperture radar (SAR) system. To make an improvement without increasing the system complexity, antenna pattern synthesis is a feasible method. To this end, a novel algorithm that can shape the mainlobe and suppress the range ambiguities simultaneously by relaxing the problem as a semidefinite relaxation (SDR) programming problem is proposed here for the first time. Compared to the algorithm with global optimization, the presented algorithm could find the desired pattern without the large occupation of computing resources and has great potential in raising the performance of SAR system. In addition, some simulations are carried out, and the results prove that the proposed algorithm has the superior ability to suppress the range ambiguities while controlling the beamwidth and dynamic range ratio (DRR). [ABSTRACT FROM AUTHOR]