Research On Interference Suppression Of High Frequency Radar Based Upon Smart Array

High Frequency Surface-Wave Radar (HFSWR) utilizes the surface-wave mode of vertical polarization electromagnetic wave propagation over sea water to detect targets of ships and aircrafts at distance beyond the line of sight. One of the most serious interference that corrupts the performance of HFSWR systems is the ionosphere clutter, since signals reflected by the ionosphere always find its way back to the receiving array, thus impose negative affects to our systems. A major thrust of the dissertation is the suppression of this kind of interference.With the development of radar technology, the intrinsic defects of traditional antenna array greatly restrict the system performance; therefore research on the compact receiving array of HFSWR becomes urgency. In this paper we focus on the superdirective circular array antenna.Firstly, the characteristic of the circular receiving array is studied, and one kind of superdirective array design approach is presented. Then, we discuss the influences that the ground screen acts on the equispaced linear array and the circular array respectively. The ground screen is utilized to obtain enhanced mirror affect, yet due to the disequilibrium of the electricity feeding, the coupling loses balance, which results in a shift of zero point of the vertical pattern . To prove the result, we simulate the coupling currents of the ground screen with SuperNEC, and analyze the effects of coupling currents on pattern in quantity. In this dissertation , a de-coupling analytical method is presented based on the actual measured pattern in aspect with linear arrays, then the method is applied in four-element array to yield satisfactory results.Secondly, the dissertations gives two array synthesis methods with aspect to circular array to cancel the ionosphere clutter,one is the circular max directivity synthesis method under condition of vertical pattern zero point restriction,the other is the circular max directivity synthesis method under condition of vertical pattern zero point restriction and efficiency restriction. The synthesis method could cancel the ionosphere clutter efficiently.Lastly, a kind of linear array composed by circular array is designed; the max directivity synthesis method under condition of vertical pattern zero point...