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This letter presents a new approach to synthesize patterns of a phased-array-fed shaped-reflector antenna for digital beamforming (DBF) synthetic aperture radar (SAR). This type of reflector antenna is capable of radiating different broad transmitting beams under phase-only control and can generate narrow receiving beams using DBF technique in the elevation direction, which is applicable to a high-resolution wide swath (HRWS) SAR system. The linear array feed locates at the defocused area of the reflector, which can enhance the beam reconfiguring ability. The elevation patterns are optimized mainly by adjusting the excitation coefficients of the array feed using improved Projection Matrix Algorithm (PMA). The azimuth patterns are optimized mainly by adjusting the reflector shape using Differential Evolution method with Global and Local neighborhood (DEGL). The patterns of the shaped reflector antenna fed by a defocused feed array are effectively synthesized, including scanning and reconfiguring beams. A numerical analysis is performed that validates the effectiveness of the approach. The beam direction, beamwidth, and sidelobe level requirements are all met.