Target flying mode identification and altitude estimation in Bistatic T/R-R HFSWR

The monostatic high frequency surface wave radar (HFSWR) can not detect the target altitude information directly and lacks the capability of classifying whether the aircraft is flying over the horizon, which is essential for the air threat assessment. In this paper, with a transmit-receive (T/R) station and a receive-only (R) station HFSWR (T/R-R HFSWR), the aircraft is assumed to be flying in one of two modes: over the horizon or within the line of horizon. A simultaneous identification and estimation (SIE) algorithm is proposed to identify the flight mode and estimate the target altitude with two levels of multiple model approach. The multiple model approach is applied at two levels: within each flight mode-conditioned altitude estimation model set and across all the mode-conditioned altitude estimation model sets. In order to construct completely observable estimation model, these novel altitude model sets fuse the target echoes of T/R and R receivers with different fusion approaches. Simulations and real trials demonstrate that the presented model can identify flight mode and estimate the target height with small errors.