In this paper, self-matching rectifiers for enhanced input dynamic range are demonstrated. The method is based on an artificial transmission line, which consists of a stepped-impedance transmission line loaded with shunt varactors. The output DC voltage of the rectifier is fed back to the varactors to control the effective electrical length and characteristic impedance of the line. Because this bias voltage changes as the power input to the rectifier changes, a matching network that maintains impedance matching regardless of the input power can be developed without additional circuits, thus substantially improving the input dynamic range. The experimental results for prototype rectifiers show a dynamic range as wide as 25 dB with only a single Schottky diode, an improvement of 11 dB over the rectifier with a conventional matching scheme, in which the conversion efficiency remains above 50%. The effectiveness of the proposed method is also verified with the experimental results for rectennas based on the demonstrated rectifiers.

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.

This study investigates the effect of driving frequency on the ability of a dielectric barrier discharge (DBD) plasma to reduce the radar cross section (RCS) in the Ku-band. Analysis based on the Drude model suggests that the electron density of the plasma will increase with the driving frequency, implying that the plasma will be more effective in terms of RCS reduction. Experimental results based on a multifingered DBD generator reveal that an RCS reduction of up to 4.1 dB is achieved at 18 GHz, which is a 1.3 dB increase due to increasing the driving frequency from 1 to 2 kHz. Finally, the electron density, which is extracted by fitting the simulated RCS results, increased by as much as approximately 330% due to the increase in the driving frequency from 1 to 2 kHz. As the driving frequency increases, the frequency of collision between plasma particles increases. Therefore, the ionization of gas molecules is enhanced, resulting in a higher electron density. The experimental results also suggest that enhancement in the RCS reduction is larger when the electric field intensity between the two electrodes of the DBD generator is greater. As a result, the plasma becomes electromagnetically more lossy and is more effective for reducing the RCS. Experimental results are provided and analyzed based on the electromagnetic parameters used for modeling the plasma.

Jang Jae Lee, Chul Hee Cho, Min Su Choi, Chang Seok Cho, Tae Joo Oh, Yong Shik Lee, Jin Woo Yim, Heung Cheol Yoo, Hee Soo Jung, and Shin Jae You. Applied Science and Convergence Technology 2021;30:141-5. https://doi.org/10.5757/ASCT.2021.30.5.141

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)

한국전자파학회논문지 (The Journal of Korean Institute of Electromagnetic Engineering and Science)