A wide-angle reconfigurable reflectarray antenna (RRA) was designed and experimentally verified utilizing a miniaturized ring patch efficiently controllable with a single bit. Based on the merits of the miniaturization of the radiating element and an elaborate study of the quantization efficiencies of the asymmetric phase differences between the on/off states of the unit cell by optimizing a reference phase on the metasurface, highly directive beam scanning is achieved in a wide ±60˚ range in both the H-and Eplanes. Furthermore, the illumination and spillover efficiencies and focal diameter ratio (F/D) are carefully optimized, resulting in a low profile configuration with F/D=0.36. The fabricated RRA prototype was measured at 9.85 GHz (X-band) with the highest aperture efficiency of 28% and a 1 dB gain bandwidth of 530 MHz, respectively.
The absorption bandwidth of a metasurface absorber can be adjusted by varying the thickness of the substrate, shape of the conductive pattern attached on top of the substrate, or conductivity of the pattern. In this study, the bandwidth of a pixelated metallic metasurface absorber was analyzed with respect to its unit cell size. The genetic algorithm (GA) was used to determine the best combination of the metallic pixels among 16 × 16 square pixels for each unit cell size. The size of the unit cell was adjusted around the 1/2 wavelength, which guarantees the suppression of the grating lobe for the normal-incidence condition. Based on full-wave simulation results, the -10 dB reflectance bandwidth was expanded as the size of the unit cell was increased from 3/8 to 3/4 wavelength with an interval of 1/8 wavelength at the center frequency of 5.8 GHz. The results demonstrate that the absorption bandwidth of the metasurface absorber is expanded by increasing the size of the unit cell around the 1/2 wavelength.
This paper proposes a novel method for designing a dual-polarized reconfigurable reflectarray antenna (RRA) based on a symmetrically rotated sub-array operating in a single-band. To improve aperture efficiency and prevent grating lobes, a miniaturized unit cell of a rectangular ring patch with a size of 0.3λ 0 is adopted, where the λ 0 is a wavelength in free-space for a center frequency of 10 GHz. By employing the RRA with a symmetrically rotated sub-array, a significant suppression of the cross-polarization level (CPL) and a slight enhancement in peak gain are both achieved. The dual-polarized metasurface with 164 elements is assembled using a feeding structure optimized with F/D = 0.52. The beam steerable RRA is electronically controlled by a control board and has a wide beam steering range of up to ±60 • . The high aperture efficiencies of 26.2% and 27.0%, and relatively low CPLs of −22.6 and −22.8 dB for the x-and y-polarized beams were measured, respectively. Furthermore, the extended functions of the presented RRA, such as dual-polarized dual-beam steering and circular polarized beam steering, are confirmed in full-wave simulation.
In this study, a broadband metasurface absorber composed of an optimal combination of copper tiles connected with four chip resistors is designed and experimentally verified. After fixing the locations of the chip resistors and setting their resistances to 100 Ω, the genetic algorithm (GA) is utilized to design the optimal copper tile pattern for broadband absorption. The optimal combination of the copper tiles is identified by determining the states of the square tile pairs between copper or air, depending on the one or zero states of the bit sequence created by GA, respectively. The full-wave simulation results of the optimized metasurface absorber confirmed a −10 dB reflectance bandwidth within the frequency range of 6.57 to 12.73 GHz for the normal incidence condition, with the fractional bandwidth being 63.83%. The accuracy of the metasurface absorber was verified through an experimental result that matched well with the full-wave simulated one.
An extraction method is proposed for the equivalent circuit parameters of an X-band PIN diode based on waveguide measurement. For the S-parameter measurement, a network analyzer, a waveguide, a transition, two identical adapters, and a 1×2 unit cell with two PIN diodes were used, and the equivalent circuit parameters of the PIN diode were extracted from the measurement results. The thru, reflect, line calibration method was adopted to reduce undesired errors in the components used for measurement, and the equivalent circuit parameters of the PIN diode were determined from the measurement results, where the effect of adapters was corrected.
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