A compact double-dipole driver is constructed for designing quasi-Yagi antenna with enhanced bandwidth and stable high gain. It is composed of a magnetic dipole and a folded electric dipole, realised by cylinder dielectric resonator and split-ring resonator. The two dipoles operate at two close frequencies, leading to bandwidth enhancement. Meanwhile, the gains of the two dipoles are also close so that the stable gain in the operating band is obtained, which can be entirely enhanced by the zero-index metamaterial in front of the dual-dipole driver. For demonstration, an antenna prototype centred at about 9.6 GHz is implemented and measured. The simulated and measured results are given, showing good agreement.
Atmospheric visibility and turbulence are important meteorological factors in light propagation and optical communication, air quality prediction, and climate environment model. They are often measured separately by the conventional instruments, but the interaction between aerosol (closely relate to visibility) and turbulence may potentially influence their measurement accuracy. In this paper, a novel instrument, the atmospheric visibility and turbulence optical meter (AVTOM), is developed to synchronously measure atmospheric visibility and turbulence intensity through a transmission method. The atmospheric visibility is measured by the extinction principle whereas the turbulence intensity is measured by the light intensity flicker principle. We validated the measurement results by comparing them to other two conventional instruments in July 2017, at Nanjing, in southeast China. They agree well with the relative differences of 4.7% for the visibility and 3.5% for the turbulence intensity, respectively. We further demonstrated their dynamic changes under the different weather or aerosol loadings through the synchronous measurements, which may be associated with the aerosol-turbulence-interaction. Finally, we proposed a calibration method and discussed the measurement errors.
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