Time-frequency-representation-based Sea Clutter Characteristic Analysis And Sharpening Of The Sky-surface Radar

The sky-surface radar is a new kind of system radar which has separatetransmitting and receiving stations, and it adopts the working mode of skywavetransmitting-surface wave receiving, combing the advantages of both skywave andsurface radar. Comparing to skywave radar, its anti-ionospheric-disturbance is stronger,and it has farther monitoring distance than surface radar. On the other hand, due to thebistatic angle and ionospheric phase pass perturbation caused by skywave transmitting,the first-order sea clutter spectrum is widened, which may submerge the target signal.Aiming at this situation, thesis includes the following work.First, we analyze the two factors causing the spectrum widening by theoreticalcalculation and simulation. We find that the influence on spectrum widening caused bybistatic angle is relatively small, and the widening degree changes little with differentdirections. Spectrum widening is more depending on the amplitude and ionosphericphase pass perturbation’s nonlinear term.Then, we study on several common contamination-suppressing algorithms. Underdifferent conditions, we conduct simulations and analyze their performances. Throughthese analysis and simulations, we conclude the performances and point at theirboundedness.At last, we study a contamination-suppressing method based on time-frequencyanalysis. First step, we study on several time-frequency analysis algorithms and analyzetheir properties from the two perspectives of time-frequency concentration andeliminating the cross-time interference. Second, through simulations, we analyze thetime-frequency distribution of the widened first-order sea clutter spectrum. In the end,we study a method named optimal path. It can distill the the time-frequency distributioncurve to suppress the ionospheric phase pass perturbation in different situations.