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A metasurface-based polarization converter for ultrawideband radar cross-section (RCS) reduction of planar and conformal surfaces is presented in this paper. Initially, a polarization converter is designed which consists of a modified concentric double (MCD) square ring resonator-based unit cell along with an air gap in between the substrate and the ground plane. This air gap enhances the polarization conversion bandwidth (PCBW) of the converter. An ultrawide PCBW ranging from 6.3 -20.5 GHz (106%) is obtained with a high polarization conversion ratio (PCR) of 0.9 for normal incident EM waves. The conversion efficiency is also found to be stable for oblique incidences over the aforementioned band with a PCR of above 0.8 upto ±35 • angles of incidence. Later on, a checkerboard configuration of the polarization conversion metasurface (PCMS) array and its mirror array is applied on a planar as well as on a cylindrical conformal surface for reducing the radar cross section (RCS). It is observed that a consistent 10 -dB co-polarized monostatic RCS reduction is achieved with the planar PCMS surface over an ultrawideband (5.5 -20.5 GHz). Even with the cylindrical surface, nearly 10 dB RCS reduction is obtained upto central angles of 60 • over a wideband. Both the structures are simulated and measured after fabrication, and a reasonably good agreement is obtained between them.INDEX TERMS Artificial magnetic conductor (AMC), conformal checkerboard surface, polarization converter (PC), radar cross section (RCS), ultrawideband.

Articles you may be interested inGaInNAs double-barrier quantum well infrared photodetector with the photodetection at 1.24 μ m Appl. Phys. Lett. 91, 051102 (2007); 10.1063/1.2767185GaInNAs/GaAs quantum wells grown by molecular-beam epitaxy emitting above 1.5 μm Appl.High-resolution x-ray diffraction ͑HRXRD͒ and photoluminescence ͑PL͒ have been used to study the diffusion of atoms in 8-nm Ga 0.628 In 0.372 N 0.015 As 0.985 / GaAs quantum well, with and without dielectric encapsulants. These samples were repeatedly annealed in the temperature range of 680-800°C over times of up to 16 000 s. HRXRD simulations, by using dynamic scattering theory and Fick's diffusion model with a constant diffusion coefficient, demonstrate that the diffusion lengths are shorter than 2 nm under the annealing conditions studied. In this range of diffusion lengths, the transition energy E e1−Hh1 , numerically calculated from the Schrödinger equation using a potential derived from the diffusion equation, increases linearly as the square of the diffusion length. The steady-state PL blueshifts, after a fast initial blueshift due to the rearrangement of local nitrogen bonding configurations N-Ga m In 4−m ͑0 ഛ m ഛ 4͒, otherwise known as short-range order, as a function of annealing time are well fitted by using the linear function. The values of ⌬E SRO and diffusion coefficients obtained are 18-28 meV and 3.0ϫ 10 −20 -3.5ϫ 10 −18 cm 2 / s, respectively. The activation energy characterized from the diffusion coefficients at different temperatures is 3.25 eV and is not affected by the dielectric encapsulates.

Self-aligned ZnO nanorods (NRs) were grown on n-Si(100) substrate by RF sputtering techniques. The NRs are uniformly grown on 2-inch wafer along [0001] direction. Single-crystalline wurtzite structure of ZnO NRs was confirmed by X-ray diffraction. The average diameter, height, and density of NRs are found 48 nm, 750 nm, and 1.26 × 1010 cm−2, respectively. The current-voltages (I-V) characteristics of ZnO NRs/Si heterojunction (HJ) were studied in the temperature range of 120–300 K and it shows a rectifying behavior. Barrier height (ϕB) and ideality factor (η) were estimated from thermionic emission model and found to be highly temperature dependent in nature. Richardson constant (A*) was evaluated using Richardson plot of ln(Io/T2) versus q/kT plot by linear fitting in two temperature range 120–180 K and 210–300 K. Large deviation in Richardson constant from its theoretical value of n-Si indicates the presence of barrier inhomogeneities at HJ. Double Gaussian distribution of barrier height with thermionic equation gives mean barrier heights of 0.55 ± 0.01 eV and 0.86 ± 0.02 eV for two different temperature regions 120–180 K and 210–300 K, respectively. Modified Richardson plot provided two values of Richardson constant for two temperature regions. However, for higher temperature range (210–300 K), the calculated value of Richardson constant ∼123 A cm−2 K−2 was close to the ideal Richardson constant for n-Si.

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