Satellite communication systems require dual-band circularly polarized (CP) waves to integrate receiving and transmit antennas into one dual-band terminal. Polarization converters play an important role in such a scenario to convert the incoming linearly polarized (LP) signal into the transmitted CP signal. Wide-band and wide-angle performance for the transmission based dual-band polarization converters has been a challenge. In this paper, a transmission-based linear polarization to circular polarization (LP-to-CP) converter is presented using a very simple and thin metasurface based structure. The proposed metasheet is uni-layered, patterned with a circular diagonal split ring enclosed in the square ring. The idea for dual-band polarization conversion is verified with an example in which x(y) polarization is converted into LHCP(RHCP) in Ku-band (15.25~18.9 GHz), and RHCP(LHCP) in Ka-band (29.7~36.7GHz). The converter performs polarization conversion for both bands over 21% of bandwidth which is very wide. Moreover, it maintains performance over wide-angled oblique incidences. Dual-band performance is analyzed theoretically, numerically, and experimentally. The equivalent circuit model is also presented for the unit cell. This metasheet has simple and low-cost design, wide polarization conversion bandwidths, polarization diversity, and wide-angle performance which are very promising for future communication systems.

Thin, amorphous, high index, dense, low scattering & absorption (low extinction coefficient) and optical grade TiO2 films of various thicknesses are prepared by Atomic layer deposition (ALD) technique and investigated in terms of thermo-optic coefficient (dn/dT) and temperature dependent density (dρ/dT). The dn/dT and dρ/dT are calculated by modeling ellipsometric experimental data by developing appropriate optical model such as Cauchy Model. The modeled data was further modeled with Lorentz-Lorenz relation under least-square approach. The dn/dT of TiO2 films shows negative values for thin and positive values for relatively thicker films and reveals no significant changes in dn/dT and dρ/dT when film thickness increases more than ~ 200 nm. The coefficient values are calculated for a wavelength range of 380-1800 nm. The average values of (dn/dT)60nm=-4.2 ± 0.7 × 10-5 ˚C-1 and (dρ/dT)60nm=-6.6 ± 1.1 × 10-5 gcm-3 ˚C-1 at wavelength of 640 nm. The reported coefficients values are measured and calculated for TiO2 film of thickness t = 60 nm and described in detail.

In this summary, we have suggested a new technique in which destructive interference principle is incorporated into a chessboard like a reflective screen, and the proposed antenna realizes a remarkable in-band and also out-of-band backscattered energy reduction by using a metasurface (MS). Two different MS unit cells are designed to provide the resonant frequency with a zero-degree reflection phase. Metasurface unit cells are configured in a chessboard-like reflector screen to achieve the reflection phase difference of 180° ± 37° over a broadband range of frequencies to redirect the scattering field into four quadrants. It is implemented to reduce the backscattered energy level of the microstrip antenna, which is based on destructive interference principle. The simulations indicate that the proposed antenna possesses significant backscattered energy reduction from 6 GHz to 16 GHz in both x– and y– polarization and also −10 dB backscattering reduction at antenna working band (7.4–7.8 GHz) is covered. Moreover, the radiation performance is preserved well and artificial magnetic conductor (AMC) unit cells work at different frequencies which are not influenced on the radiation properties. The bistatic performance of the antenna at different frequencies is also presented. Measurements and simulations of the fabricated design coincide well and the proposed design is verified and validated successfully.

Antenna Arrays In article number 2100088, Muhammad Saleem and Yasir Saifullah design a coding artificial magnetic conductor ground to reduce wideband monostatic and bistatic radar cross section of th...