F-THETA LENS DISTORTION

The features of F-Theta lenses, the values of the characteristics of the most common models are considered. The conditions for achieving the F-Theta law and the telecentric run of the main rays in the optical scheme of the lens are identified. A formula for the distortion required to provide a linear law, depending on the angle of the inclined beam of rays relative to the optical axisis given. The criteria for the permissible error of deviation from the exact compliance with the linear law are formulated. The relevance of the development of new optical systems for F-Theta lenses is justified.

Microstrip antenna array with an inclined surface and an increased distance between patches

A new technique for designing a path antenna array with an inclined beam is proposed. It boils down to finding a certain combination of parameters that use the secondary main maxima of the diagram as the main beam and at the same time guarantee the greatest distance between the emitters that does not yet lead to the occurrence of secondary main maxima in the antenna radiation pattern. This simplifies the geometric structure of the antenna, reduces its cost, simplifies the microstrip power system, and reduces the mutual influence of individual elements in the antenna array. To combine the possibility of reducing the radio visibility of the antenna by changing the orientation of the antenna opening while maintaining its emissivity in a given viewing plane, it is possible to implement an antenna with a main beam deviated from the normal. The efficiency of reducing backscattering for the radar range due to the tilt of the antenna outside the operating frequency band of the antenna is investigated. Thus, when mechanically scanning the antenna, due to the fact that the main beam of the antenna array is deviated from the normal, it is possible to achieve a significant reduction in the average backscattering pattern of at least 25 dB. It is known that improving the safety of small aircraft at low altitudes, as well as on take-off and landing sites, is directly related to the introduction of a small weather radar, which warns of the presence of dangerous phenomena along the flight path: thunderstorms, turbulence, and wind. When the onboard radar is operating in thunderstorm or turbulence detection modes, the presence of re-reflections from the Earth's surface can lead to the formation of false areas that are dangerous for flight. You can reduce the likelihood of such false zones by spatial filtering of interference from the ground using antennas with a low level of side lobes in the lower hemisphere. The relevance of the problem of reducing the influence of interference from the ground on the correctness of the wind speed estimation in the weather radar is confirmed by publications. They are focused on filtering interference from the earth's surface in the frequency domain for ground-based weather radars or for airborne radars, but by the main beam of the alignment diagram and the rule of its elevation to avoid touching the ground. The second part of the research is devoted to reducing the influence of re-reflections from the earth on the probability of forming false areas of dangerous weather events in the weather radar. To reduce the impact of interference, it is proposed to install an antenna with an upward tilt.

Analysisof Effective Length Factors of Hinged Pitched-Roof Framed Column with Sway under Arch Effect

Aiming at the limitation of the calculated length coefficient of the gable portal rigid frame columns in the standards and regulations, which ignores the influence of the arch effect caused by the axial force of the inclined beams lope, this paper uses the elastic buckling equation of the solid-webbed articulated pitched-roof frame, considered 𝑃−𝛥 second-order effect and the arch effect of the inclined beam under uniform load together. And the length coefficient calculated is analyzed. It is concluded that the larger the slope of the inclined beam and the ratio of the rigid frame span are, the more obvious the arching effect is, and the larger the calculated length coefficient of the rigid frame column is.

Buckling Analysis of Inclined Beam-Column Structures by Using Differential Transform Method (DTM)

In this work a classical structural element inclined beam-column has been analyzed for two boundary conditions by applying a semi-analytical numerical technique differential transform method (DTM).Eigenvalues related to critical load and length, and deflection curves are presented for pinned-pinned and clamped-pinned end condition cases.