Two-step Structural Design of Mesh Antennas for High Beam Pointing Accuracy

Chinese Journal of Mechanical Engineering, Apr 2017

A well-designed reflector surface with high beam pointing accuracy in electromagnetic performance is of practical significance to the space application of cable mesh reflector antennas. As for space requirements, circular polarizations are widely used in spaceborne antennas, which usually lead to a beam shift for offset reflectors and influence the beam pointing accuracy. A two-step structural design procedure is proposed to overcome the beam squint phenomenon for high beam pointing accuracy design of circularly polarized offset cable mesh reflectors. A simple structural optimal design and an integrated structural electromagnetic optimization are combined to alleviate the beam squint effect of circular polarizations. It is implemented by cable pretension design and adjustment to shape the offset cable mesh surface. Besides, in order to increase the efficiency of integrated optimization, an update Broyden-Fletcher-Goldfarb-Shanno (BFGS) Hessian matrix is employed in the optimization iteration with sequential quadratic programming. A circularly polarized offset cable mesh reflector is utilized to show the feasibility and effectiveness of the proposed procedure. A high beam pointing accuracy in order of 0.0001º of electromagnetic performance is achieved.

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Two-step Structural Design of Mesh Antennas for High Beam Pointing Accuracy

Chin. J. Mech. Eng. Two-step Structural Design of Mesh Antennas for High Beam Pointing Accuracy Shuxin ZHANG 0 1 Jingli DU 0 1 Wei WANG 0 1 Yali ZONG 0 1 Xinghua ZHANG 0 1 0 Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology , Beijing 100094 , China 1 Key Laboratory of Electronic Equipment Structure Design of Ministry of Education, Xidian University , Xi'an 710071 , China A well-designed reflector surface with high beam pointing accuracy in electromagnetic performance is of practical significance to the space application of cable mesh reflector antennas. As for space requirements, circular polarizations are widely used in spaceborne antennas, which usually lead to a beam shift for offset reflectors and influence the beam pointing accuracy. A two-step structural design procedure is proposed to overcome the beam squint phenomenon for high beam pointing accuracy design of circularly polarized offset cable mesh reflectors. A simple structural optimal design and an integrated structural electromagnetic optimization are combined to alleviate the beam squint effect of circular polarizations. It is implemented by cable pretension design and adjustment to shape the offset cable mesh surface. Besides, in order to increase the efficiency of integrated optimization, an update Broyden-Fletcher-Goldfarb-Shanno (BFGS) Hessian matrix is employed in the optimization iteration with sequential quadratic programming. A circularly polarized offset cable mesh reflector is utilized to show the feasibility and effectiveness of the proposed procedure. A high beam pointing accuracy in order of 0.0001º of electromagnetic performance is achieved. Cable mesh reflector antennas; Structural design; Beam squint; Beam pointing accuracy - In recent years, the stringent requirements on large space reflectors become demanding for high electromagnetic performance [ 1 ]. As for space applications, circular polarizations are usually used in spaceborne antennas. With circularly polarized feeds, there exists a beam squint phenomenon in offset reflector antennas [ 2 ]. The squint angle, which is manifested by a small beam shift of the radiation pattern in the plane perpendicular to the principal offset plane, can significantly affect the beam pointing accuracy. As one of the most widely used space antennas, cable mesh reflector antenna has attracted much attention due to its advantages of large diameter, light weight, and reasonable cost [ 3 ]. Similarly with the smooth solid reflectors, the beam squint phenomenon can also be observed in offset cable mesh reflector antennas with reflecting mesh leakage [ 4, 5 ]. The beam squint angle should be taken into account for space applications such as satellite communications, deep-space telemetry, and radio astronomy [2], which concentrate more on beam pointing accuracy. With the stringent requirements on space reflector antennas, the compensation technology to overcome the antenna pattern degradation including beam squint to achieve high pointing accuracy becomes more demanding [ 6 ]. Since the simple formula which accurately predicts the squint angle in circularly polarized offset reflectors was proposed by ADATIA and RUDGE [ 7 ], the beam squint phenomenon and its compensation method have attracted many authors’ interests. A squint compensation method by properly tilting the feed to make the interpreted angle between the incident beam and the radiated beam zero is a natural choice for symmetrical reflectors with off-focus feeds [ 8 ]. A squint free approach for symmetrical dual reflector antennas is also proposed by properly choosing be achieved in the antenna structural design. This technology not only can compensate the beam squint angle of circular polarizations, but also can produce a well-designed cable mesh reflector with on-focus feeds. Comparing with the compensation methods proposed by electromagnetism designers, the limited weakness of aforementioned methods can be overcame. This paper is organized as follows. Section 2 of this study outlines the procedure of the two-step structural design technology. In this technology, an update BroydenFletcher-Goldfarb-Shanno (BFGS) Hessian matrix is employed to increase the efficiency of optimization iteration. In section 3, a circularly polarized offset cable mesh reflector is utilized to show the feasibility and effectiveness of this procedure with an on-focus feed to achieve high beam pointing accuracy in electromagnetic performance. The major achievements are summarized in section 4. geometrical parameters [ 9 ]. Furthermore, XU and RAHMAT-SAMII [ 2 ] summarized the beam squint compensation methods, and proposed a compensation technology by optimally displacing circularly polarized feeds in the perpendicular plane to obtain high beam pointing accuracy. However, these methods in Refs. [ 2, 7–9 ] are presented from the simple electromagnetic disciplinary, and they are just practical for undistorted r (...truncated)


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Shuxin ZHANG, Jingli DU, Wei WANG, Xinghua ZHANG, Yali ZONG. Two-step Structural Design of Mesh Antennas for High Beam Pointing Accuracy, Chinese Journal of Mechanical Engineering, 2017, pp. 604-613, Volume 30, Issue 3, DOI: 10.1007/s10033-017-0134-0