Abstract
Maritime safety issues have aroused great attention, and it has become a difficult problem to use the sky-wave over-the-horizon radar system to locate foreign targets or perform emergency rescue quickly and timely. In this paper, a distributed multi-point sky-wave over-the-horizon radar system is used to locate marine targets. A positioning algorithm based on the Doppler frequency is proposed, namely, the two-step weighted least squares (2WLS) method. This algorithm first converts the WGS-48 geodetic coordinates of the transceiver station to spatial rectangular coordinates; then, introduces intermediate variables to convert the nonlinear optimization problem into a linear problem. In the 2WLS method, four mobile transmitters and four mobile receivers are set up, and the Doppler frequency is calculated by transmitting and receiving signals at regular intervals; it is proven that the 2WLS algorithm has always maintained a better positioning accuracy than the WLS algorithm as the error continues to increase with a certain ionospheric height measurement error and the Doppler frequency measurement error. This paper provides an effective method for the sky-wave over-the-horizon radar to locate maritime targets.
Highlights
The sky-wave over-the-horizon radar (OTHR) uses ionospheric reflection or refraction to realize the propagation of radio waves
The state of the ionosphere determines the positioning performance of the skywave over-the-horizon radar system, and the models describing the ionosphere state are usually divided into the International Reference Ionosphere (IRI) model, the Chapman ionosphere model and the multiple pseudo-parabolic model (MQP) [1]
The MQP model is used to describe the OTHR system in which multistatic radar signals travel through the ionosphere
Summary
The sky-wave over-the-horizon radar (OTHR) uses ionospheric reflection or refraction to realize the propagation of radio waves. It mainly uses shortwave frequency bands, usually 3–30 MHz, and its range can break through the limitations of the curvature of the earth beyond the line-of-sight [1], and the over-the-horizon radar is mainly used for early warning [2]. A signal model of the sky-wave over-the-horizon radar system based on the Doppler frequency measurement is established to obtain a positioning optimization equation, and a two-step weighted least square method (2WLS) is proposed to transform the highly non-linear optimization problem into a linear optimization problem. The simulation shows that the 2WLS algorithm has better positioning accuracy than the WLS algorithm within a certain range of ionospheric height measurement error and the Doppler frequency measurement error
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