*3.4. E*ff*ect of Bistatic Angle on RCS*

Figure 11 shows the simulated total RCSs containing the first- and second-order RCSs for different bistatic angles. It is obvious that the Bragg peaks, both the hydrodynamic and electromagnetic peaks for the second-order scatter and additional peaks caused by six DOF oscillation motion move closer to zero Doppler frequency while the bistatic angle is increasing. Furthermore, as the bistatic angle increases, the amplitudes of the second-order RCSs decrease, and the modulation effect caused by the platform motion is weakened. It should be noted that, from Equation (58), the second-order electromagnetic peaks may be far away from the Bragg peaks or even diminished from the total RCS curve for a large bistatic angle, for example φ<sup>0</sup> = 85◦ as shown in Figure 11.

**Figure 10.** Simulated RCSs for a dual-frequency six DOF oscillation motion model. (**a**) First-order RCS; (**b**) second-order RCS; (**c**) total RCS; (**d**) zoomed in view of the positive Doppler frequency in (c).

**Figure 11.** Simulated total RCSs containing first- and second-order RCSs for different bistatic angles.
