In this paper, an ultra-wide band modified slot-sinuous antenna has been designed to enhance bistatic radar cross section (RCS) response. The design procedure consists of adding three or five parasitic ellipses openings to each of the slot-sinuous arm cells. The parasitic ellipsis allows to control bistatic RCS without impacting antenna radiation characteristics. Parasitic ellipses opening dimensions are small compared to the relative wavelength of the signal on each active region of the antenna. The ellipses distributed on sinuous antenna arm are scaled by the same expansion coefficient used to design the antenna itself. In the proposed design, ellipses parameters such as ellipses axis, radial position, and relative angle position on the sinuous cell are key parameters to be optimized for bistatic RCS reduction. The total number of designing parameters is finite, but their combination is infinite, which leads to the possibility of designing different antennas based on the required designing goals. The proposed solution and the results presented in this work show the applicability of the designing parameters to control bistatic RCS on active region antennas.