*3.4. Simulation 4: Simulated Sea Clutter Spectrum for Di*ff*erent Wind Directions*

The simulation results of the first-order sea clutter spectrum at wind directions of 0◦, 45◦, 90◦, 135◦, 180◦, and 225◦ are shown in Figure 11a–f. Here, we set the elliptical eccentricity as e = 0.7, frequency as 4.7 MHz, shipborne platform velocity *vR* = 8 km/h, and heading ϕ*<sup>R</sup>* = 0◦.

**Figure 11.** Simulation results of the first-order sea clutter spectrum for a CTSR bistatic HFSWR at different wind directions: (**a**) 0◦, (**b**) 45◦, (**c**) 90◦, (**d**) 135◦, (**e**) 180◦, and (**f**) 225◦.

It can be seen from Figure 11 that the range of broadening of the first-order sea clutter spectrum of a coast–ship bistatic HFSWR remained unchanged under different wind conditions. Moreover, the width of the first-order sea clutter of the coast–ship bistatic HFSWR was always less than that of the monostatic shipborne HFSWR under the same platform velocity and radar configuration. However, the comparative relationship between the amplitude of the left first-order spectrum and right first-order spectrum was changed, and the related blind area had a different influence on target detection.

Under the condition of 180◦ wind direction, the average amplitude of the right first-order spectrum relative to the underlying noise was 38 dB, while the average amplitude of the left first-order spectrum was 21 dB, i.e., a difference of 17 dB. Thus, for a moving target with amplitude of 30 dB, if its elliptical velocity were within the right first-order spectrum, it would be submerged completely by sea clutter. However, it could be detected easily if its elliptical velocity were within the left first-order spectrum. For the wind condition of 135◦, the situation was the reverse of the 45◦ condition.
