Mode identification and positioning accuracy improvement using forward-based receivers for OTHR

Target tracking of over-the-horizon radar (OTHR) faces the challenge of low detection probability, low sampling rate, low measurement accuracy and multipath propagation. Both mode recognition of multipath propagation and target localization, significantly affect data association and estimate updating. In this paper, a scheme of measurement fusion of OTHR and forward-based receivers (FBRs) is presented to identify propagation modes and improve positioning accuracy. A coordinate transformation formula related to the target height is derived, and the measurements of FBRs are fused to obtain the preliminary estimates of the target state and ionosphere heights via an iterative least square method. Based on the above position estimate and OTHR measurements, a maximum-likelihood-estimation-based rule is proposed to identify the propagation/clutter modes. Finally, a minimum variance estimation method is given to improve positioning accuracy by fusing the associated data from OTHR and FBRs in ground coordinates. Simulation results show that the identification of propagation modes is satisfactory, the ionospheric heights and target heights can be estimated, and there is significant positioning accuracy improvement through fusing measurements of OTHR and FBRs.