*3.3. Simulation 3: Simulated Space–Time Distribution for Di*ff*erent Radar Frequencies*

The space–time distribution of the Doppler frequency shift of the first-order sea clutter and the simulation results of the first-order sea clutter spectrum for a CTSR bistatic HFSWR at different frequencies are shown in Figures 9 and 10, respectively. Here, we set the elliptical eccentricity as e = 0.134, shipborne platform velocity *vT* = 8 km/h (approximately 4.3 knots), heading ϕ*<sup>R</sup>* = 114◦, and wind direction as 90◦.

**Figure 9.** Space–time distribution of the Doppler frequency shift of the first-order sea clutter for a CTSR bistatic HFSWR at different frequencies: (**a**) *f* = 4.7 MHz and (**b**) *f* = 10 MHz.

**Figure 10.** Simulation results of the first-order sea clutter spectrum for a CTSR bistatic HFSWR at different frequencies: (**a**) *f* = 4.7 MHz and (**b**) *f* = 10 MHz.

It can be seen from Figure 10 that the widths of the sea clutter blind area of a monostatic shipborne HFSWR at different frequencies but with a constant platform velocity were similar, while their central positions differed. Conversely, both the range of broadening of the first-order sea clutter spectrum and the width of the sea clutter blind area of a coast–ship bistatic HFSWR changed with radar frequency.
