An innovative aperiodic phased array antenna architecture with quantised excitation for space‐borne synthetic aperture radar (SAR) is presented. Compared to traditional periodic arrays, the proposed array antenna enjoys two major advantages including (i) much higher overall power efficiency and (ii) phase‐only control for both transmitting (TX) and receiving (RX) patterns to fit different space SAR beam shaping and steering requirements. The unprecedented studies on the quasi‐optimum TX and RX pattern strategies for space SAR are carried out and this strategy is utilised in the design of the proposed aperiodic phased array. Performance of the proposed array when being applied to space SAR are evaluated. Moreover, the authors obtained positive results which endorse the design.