Study On Methods Of DOA And Polarization Estimation Based On Airborne Electromagnetic Vector Sensor Array

The electromagnetic vector sensor array signal processing is a new emerging subdiscipline in array signal processing domain. In recent years, DOA and polarization parameters estimation of signals using array of electromagnetic vector sensors has become a hotspot. It is widely used in radar, sonar and communication etc, and arouses great research interest.The research on DOA and polarization parameters simultaneous estimation using electromagnetic vector sensor array is of great significance in practical application and academy. People have used traditional scalar sensor array on DOA estimation for a long time, and have massive academic achievements. Through this system we cannot obtain the integrated electric and magnetic fields information but only the information on one field component. The array element output only reflected intensity and the absolute phase of the received signal. The lack of information will eventually affects the algorithm performance. However, EMVS can provide complete electric and magnetic fields, which is composed of three orthogonal electric dipoles and three corresponding orthogonal magnetic dipoles. Not only it can use its array geometry structure to acquire the spatial information of the signal, but also can acquire all polarization information. Electromagnetic vector sensor array is space placed array systems in a certain way by EMVS. It can not only use the geometric structure of the array to space domain sampling for spatial information, but also use electromagnetic vector sensors to obtain all polarization information of the signals. So it has superior information acquire ability than the common arrays. Compared with traditional scalar sensors, electromagnetic vector sensor array has a better performance: steady detective ability, stronger anti-jamming ability as well as higher space resolution.At present the mass of method used in electromagnetic vector sensor array signal processing domain is based on supposition of the Gaussian white noise and the steady signal. But in practical environment, the white Gaussian noise supposition may not always be true, and many signals exited are not steady. For example, most man-made signals ,such as BPSK, FSK, AM signals, exist in the cyclo stationary, and LFM signals used in radar applications. As a result, the performance of subspace-based DOA and polarization estimation techniques may degrade when dealing with non-stationary signals. In addition, airborne electromagnetic vector sensor array is installed on uneven surface of the aircraft, the presence of the reflection waves causes airborne electromagnetic vector sensor array model to change: electric dipoles components e x=0, ey?0 , magnetic dipoles components h z? 0.Many conventional algorithm will lapse in airborne electromagnetic vector sensors.In this paper, for the characteristics of the airborne electromagnetic vector sensor array is rich in redundant information, combined with the specific characteristics of the signal,launch in the DOA and polarization parameters estimation at the same time under Gaussian colored noise signal.As the Gauss Blind of the fourth-order cumulant, signal parameter estimation methods based on the fourth-order cumulant are applicable to arbitrary Gaussian noise. Moreover, as a result of fourth-order cumulant expansion of the array, which reduces the requirements on the array structure. According to fourth-order cumulant properties, the paper discusses the airborne electromagnetic vector sensors in arbitrary Gaussian noise environment of the signal frequency, two-dimensional direction of arrival angle and polarization parameters joint estimation algorithm and the algorithm is applicable to arbitrary array.For a special kind of non-stationary signals - cyclostationary signals (such as BPSK signal) incidence to arbitrary array composed by airborne electromagnetic vector sensor, use the cyclo stationary properties, constructed the fourth-order cycle cumulant matrix, propose cycle ESPRIT algorithm based on fourth-order cyclo cumulant. Cycle ESPRIT algorithm utilize shift invariant features of the array structure, so that parameters can be directly calculated. unlike the cycle MUSIC algorithm to make regional search, solve large compute capacity problems and ensure the estimation accuracy at a relatively low signal-noise ration circumstances.The above-mentioned two-dimensional DOA parameters estimation algorithm is completed in reference to airborne coordinate system. When the carrier attitude changes, for the position of airborne vector sensor array are fixed in relation to carrier and move with aircraft, so that the angle between the objectives and the array will change. So if refer to the earth coordinate system, the performance of signal processing algorithms will be effected. Hence there must employ appropriate methods of correction to make conversion from airborne coordinate system to earth coordinate system to eliminate the impact.