The scattering characteristics of a blunt cone with electrically large size covered by inhomogeneous plasma sheath are investigated from $S$-band to Ku-band frequencies by using physical optics (PO) method. PO formulations are derived for conductive objects with inhomogeneous plasma coverage. The numerical results indicate that the plasma inhomogeneity greatly influences the radar cross section (RCS). However, under different incident wave conditions, particularly in the high-frequency band, the scattering results are almost consistent for sine plasma frequency profile and both plasma and collision frequency with sine profile except that the amount of RCS exhibits a little difference at some specific frequencies, indicating the reasonability of the plasma sheath model with only inhomogeneous plasma frequency distribution. Moreover, the effects of the plasma parameters on inhomogeneous plasma scattering are also analyzed.

3-D time-varying and spatially nonuniform plasma is applied using the finite-difference time-domain algorithm in investigating the effects of electromagnetic (EM) wave scattering in the plasma sheath. The plasma sheath is stratified in space, and three types of electron density in time-varying forms are assumed. The characteristics of different time-varying forms are analyzed using radar cross section (RCS). In addition, the effects of RCS change with time at Sand L-bands are investigated using electron density as the time variable. In the condition of timevarying and spatially nonuniform plasma sheath, the attenuation of EM wave is affected by different time-varying regularities of electron density (n _e ). The RCS varying with time is related to the change rate of n _e .

The novel design of a single-sided left-handed metamaterial (LHM) based only on modified circular electric resonators (MCERs) is presented experimentally and numerically in this letter. A capacitive gap is introduced in the middle arm of the electric resonator. Through adjusting the geometrical dimensions properly, the two frequency bands corresponding to negative permittivity and permeability overlap, which is validated by the parametric retrieval algorithm and equivalent circuit analysis. Furthermore, a dual-band LHM is achieved by combining two kinds of MCERs within the same unit cell. Compared to previous composite structures, the MCERs have the advantages of simple pattern, flexible design and fabricating three-dimensional LHMs readily.

The dielectric coefficient of a weakly ionised dusty plasma is used to establish a three-dimensional time and space inhomogeneous dusty plasma sheath. The effects of scattering on electromagnetic (EM) waves in this dusty plasma sheath are investigated using the auxiliary differential equation finite-difference time-domain method. Backward radar cross-sectional values of various parameters, including the dust particle radius, charging frequency of dust particles, dust particle concentration, effective collision frequency, rate of the electron density variation with time, angle of EM wave incidence, and plasma frequency, are analysed within the time and space inhomogeneous plasma sheath. The results show the noticeable effects of dusty plasma parameters on EM waves.

The electromagnetic (EM) scattering properties of the chaff cloud in airflow are rarely addressed in previous works. To deal with this issue, two types of the chaff clouds in airflow are first established based on aerodynamics theories. Then, the K-means algorithm is utilized to divide the chaff cloud into several parts according to the elements’ number density. Meanwhile, the EM transmission property of each part is extracted with the help of the method-of-moments (MoM). Based on this, the vector radiative transfer (VRT) method is introduced to estimate the bistatic scattering coefficients of the established chaff clouds with 40 million elements, which takes into account the radiation pattern of the transmitting antenna and the EM coupling between chaff elements. To speed up the VRT program, parallel computing technologies are adopted. Besides, the verifications of the VRT method are proposed by performing simulations with a numerical method and conducting experiments. Comparative investigations indicate that the results predicted by the proposed VRT method have a good agreement with experimental ones with an error of less than 10%.

The radar cross section (RCS) reduction of hypersonic targets by radar absorbing materials (RAM) coating under different reentry cases is analyzed in the C and X bands frequency range normally used for radar detection. The physical optics method is extended to both the inhomogeneous plasma sheath and RAM layer present simultaneously. The simulation results show that the absorbing coating can reduce the RCS of the plasma cloaking system and its effectiveness is related to the maximum plasma frequency. Moreover, the amount of the RCS decrease, its maxima, and the corresponding optimal RAM thickness depend on the non-uniformity and parameters of the plasma sheath. In addition, the backward RCS of the flight vehicle shrouded by plasma shielding and man-made absorber is calculated and compared to the bare cone.