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When the aircraft moves through the atmosphere at a very high speed, the aircraft will experience intense friction with the surrounding atmosphere, which causes the air to be ionized into plasma, thus producing a plasma flow field around it. Plasma is constantly generated on the windward side of the aircraft and flows backwards. The velocity of plasma is different from that of the aircraft. In addition to the dispersion characteristics of the plasma and the non-uniform distribution around the target, the plasma flow field will produce the effects of amplitude, frequency and phase modulation on the incident radar wave, which will change the electromagnetic scattering characteristics of the target.   In order to reproduce the non-uniform Doppler phenomenon in the flow field under electromagnetic wave irradiation, the plasma echo spectrum is measured experimentally in the JF-10 wind tunnel of the Institute of Mechanics, the Chinese Academy of Sciences. The echo spectrum data of S band and C band are obtained by using a measurement system composed of signal source, circulator, antenna and spectrometer, and based on the measured data the one-dimensional range profile of the plasma coated target is simulated, and the results show that the plasma flow field has a spectrum modulation effect on the target. When the speed of the flow field cannot be compensated for accurately, the spectral modulation effect will further cause the one-dimensional range profile to defocus, which will affect the ability of radar to detect and track the object. The preliminary analysis shows that the effect is caused mainly by the inhomogeneous velocity distribution of plasma flow field and the sudden change of medium parameters when the shock wave arrives. This experiment can provide data support for verifying the electromagnetic characteristics modeling method of plasma flow field.

Echo spectrum modulation characteristics of plasma flow field simulated by wind tunnel