A dual-polarized 4×4 scanning phased array antenna with leaky-wave enhanced lenses operating at 28 GHz is presented. Such an antenna can be used for point-to-point 5G communications that require high gain, wide bandwidth, and limited steering ranges. The proposed array has a periodicity of two wavelengths, and the resulting grating lobes are suppressed by directive and steerable array element patterns. To achieve a low-cost and low-profile solution, the leaky-wave antenna feeds are designed in printed circuit board and the lenses are made of plastic. The lenses are optimized in the near-field region of the feeds, with the goal of maximizing the array element aperture efficiency. The array performance obtained from the proposed approach is validated by full-wave simulations, showing a 27.5 dBi broadside gain at 28 GHz and a steering capability up to ±20 • with 2 dB of scan loss. An antenna prototype was fabricated and measured. Measurement results are in excellent agreement with full-wave simulations. The prototype antenna, at broadside, achieves a 20% relative bandwidth and a gain of 26.2 dBi.
We present a freely accessible graphical user interface for analysing antenna-fed Quasi-Optical systems in reception. This analysis is presented here for four widely used canonical Quasi-Optical components: parabolic reflectors, elliptical, extended hemispherical, and hyperbolic lenses. The employed methods are Geometrical Optics and Fourier Optics. Specifically, Quasi-Optical components are illuminated by incident plane waves. By using a Geometrical Optics based propagation code, the scattered fields are evaluated at an equivalent sphere centred on the primary focus of the component. The Fourier Optics methodology is then used to represent the scattered fields over the focal plane as Plane Wave Spectrum. A field correlation between this spectrum and the antenna feed radiating without the Quasi-Optical component is implemented to evaluate the induced open-circuit voltage on the feed in reception. By performing a field matching between these two spectral fields, feed designers can optimize the broadside and/or steering aperture efficiencies of Quasi-Optical systems in a fast manner. The tool is packaged into a MATLAB graphical user interface, which reports the efficiency terms, directivity and gain patterns of antenna-coupled Quasi-Optical systems. The described tool is validated via full-wave simulations with excellent agreement.
Drude's description of the response of lowtemperature gallium arsenide to optical pulse excitation is used to evaluate the components of a time-domain Norton equivalent circuit of a photoconductive antenna (PCA) source. The saturation of the terahertz (THz) radiated power occurring at large optical excitation levels was previously associated by the scientific community to radiation and charge screening of the bias. With the present circuit, we are able to model accurately the measured saturation as only due to the EM feedback from the antenna to the bias. The predicted THz radiated power is shown to match very accurately the measurements when the circuit is combined with an accurate description of the experimental conditions and the modeling of the THz quasi-optical (QO) channel.
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