In this study, a method was experimentally verified for further reducing the radar cross-section (RCS) of a two-dimensional planar target by using a dielectric rim in a dielectric barrier discharge (DBD) plasma generator using a frequency selective surface (FSS) as an electrode. By designing the frequency selective surface such that the passbands of the radar signal match, it is possible to minimize the effect of the conductor electrode, in order to maximize the RCS reduction effect due to the plasma. By designing the FSS to be independent of the polarization, the effect of RCS reduction can be insensitive to the polarization of the incoming wave. Furthermore, by introducing a dielectric rim between the FSS electrode and the target, an additional RCS reduction effect is achieved. By fabricating the proposed plasma generator, an RCS reduction effect of up to 6.4 dB in X-band was experimentally verified.

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This study investigates high-power wireless power transfer(WPT) with a wide charging area for large drones. The overall size of the receiving coil(Rx-coil) connected to the leg of the drone on the bottom side is 420×420×10 mm. Transmitting coils(Tx-coils) of three different shapes are individually optimized and combined to achieve a uniform magnetic field intensity and high power transfer efficiency(PTE) retention rate. The overall dimension of %the Tx-coil including the case thickness is 1,000×1,000×105 mm. The quality factors of the optimized Tx-and Rx-coils are 120 and 54, respectively, expressing a high PTE according to the transmission and misalignment distances. Based on the center between the coils, the PTE is 91 % and 80 % at a transmission distance of 50 mm and 300 mm, respectively. The PTE is 89.5 % when the Rx-coils are positioned at a misalignment distance of 285 mm, which indicates the edge of the Tx-coil in the charging area. The coils are connected to various equipment(e.g., signal source, Tx-and Rx-modules, load, etc.) to verify the WPT system. The system efficiency considering loss is 69 % because the input and output powers are 174.7 W and 120.3 W, respectively. In addition, an electromagnetic wave is measured below the electromagnetic interference standard.

In this paper, to analyze the dispersive characteristics of plasma, a dispersive model suitable for the finite-difference time-domain (FDTD) method is proposed. The dispersive characteristics of plasma with varying electrical properties according to frequency were accurately and efficiently expressed using the modified Lorentz dispersive model. The coefficient of the modified Lorentz dispersive model was extracted by applying complex curve fitting based on the weighted least squares method. The method of applying the modified Lorentz dispersion model to the FDTD is discussed. The plasma model based on the modified Lorentz dispersion model proposed in this paper was verified to match the data of the dielectric barrier discharge (DBD) plasma generator from dielectric slab equivalent modeling. The accuracy of the proposed FDTD algorithm based on the modified Lorentz dispersive model was verified by comparison with the results of the broadband radar cross-section (RCS) measurement experiment.

A dielectric barrier discharge (DBD) plasma generator with a face-to-face multilayer structure for radar cross section (RCS) reduction is designed. The generator includes two electrodes of 16×0.5 cm 2 size, facing each other. Because the electrodes are on the plane that is parallel to the direction of the incident wave, the effect of the generator on the RCS of the target is significantly reduced, particularly when compared to conventional parallel plate-type generators. This simplifies the design procedure for the DBD generator and maximizes the effect of the plasma on RCS reduction. For experimental verification, 42 layers of the proposed generator with a distance of 5 mm between the two electrodes are stacked to reduce the RCS of a 20×20 cm 2 -sized copper plate. Experimental results demonstrated a reduction of approximately 3.2 dB in the RCS in the X-band.