Detection of Radar Target Wrapped in Plasma Sheath Based on Intrapulse Energy Focusing

When a high-speed target travels through the Earth's atmosphere, a plasma sheath forms on the target surface due to thermal ionization. Through theoretical calculation and wind tunnel measurements, we have known that the plasma sheaths wrap the target, most of which are distributed in a small area around the target, and their velocity is not equal to the target's velocity, but decreases from inside to outside. Owing to the range-Doppler coupling effect of a linear frequency modulation signal, the spectral peaks belonging to the target and plasma sheath after pulse compression are not at their true distances. The intensity of the plasma sheath echo depends on multiple factors, showing a strong time-varying characteristics. Therefore, it is difficult to track the target wrapped in plasma sheath. Considering that the target echo contaminated by the plasma sheath after pulse compression will include one target spectral peak and several plasma sheath spectral peaks, an intrapulse energy focusing detector is proposed, which is treated as a special case of multiple sinusoids detection. Its detection performance is analyzed and verified by simulation results, which show that the detector can effectively detect high-speed targets with plasma sheath and reduce the signal-to-noise ratio threshold.