New electromagnetic (EM) structures are demonstrated to realize low-radar-cross section (RCS) antennas by making effective use of frequency-selective absorber (FSA). According to the well-known reciprocity principle, the two-layered FSA can be considered as an actual receiving antenna and then transformed to a circularly polarized (CP) antenna. At the radiation state, a truncated patch resonator on the bottom layer is fed by a coaxial probe so as to produce CP wave, and it further excites the slots on the upper layer, resulting in its radiation toward free space, and when the antenna at the stealth state, the detective incident wave can be effectively absorbed outside the radiation band, thus achieving RCS reduction. The design strategies are then explained and verified with the aid of the corresponding equivalent circuit models. Two examples of 2 × 2 and 4 × 4 antenna arrays were designed to validate the flexibilities of the proposed design method. Finally, the 4 × 4 antenna array was fabricated and measured, and reasonable agreement is achieved.