Dual-reflector antennas are widely used in astronomical observations and satellite communication.Structural deformations of the reflectors for radio telescopes are inevitable in outside working conditions due to exter...Dual-reflector antennas are widely used in astronomical observations and satellite communication.Structural deformations of the reflectors for radio telescopes are inevitable in outside working conditions due to exterior environment loads,which will cause distortion in the surface of the primary reflector and displacement of the subreflector,then lead to gain degradation and misalignment.In this paper,the influence and correction of misalignment in a dual-reflector antenna have been studied.From the perspective of wavefront aberration,a method is proposed to correct the wavefront primary aberration by adjusting the subreflector position.The characteristics of wavefront errors caused by structural deformation of the reflector have been analyzed,and relationships between the position motions of the subreflector and the Seidel wavefront aberrations are derived.The adjustment quantities of the subreflector are also derived.The results show the appropriate positional change of the subreflector in the lateral and axial directions can effectively correct the effects of the tilt and defocus in the primary aberrations caused by antenna structural deformations.展开更多
A new method based on the parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas, that are distorted by gravity, to improve their electromagneti...A new method based on the parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas, that are distorted by gravity, to improve their electromagnetic(EM) performance. Both the features of shaped surface and the relationship between optical path difference(OPD) and far field beam pattern are employed. By describing the shaped dualreflector surface as a standard discrete parabola set, we can utilize the optical features of the standard Cassegrain system in the classical OPD relationship. Then, the actual far field beam pattern is expressed as the synthesis of ideal beam and error beam by decomposing subreflector adjustment parameters using a mechanical-electromagnetic-field-coupling-model(MEFCM). Furthermore, a numerical method for determining optimal subreflector position is presented. The proposed method is based on the iteration technique of subreflector adjustment parameters, and the optimal far field pattern is used for the iteration. The numerical solution of optimal adjustment parameters can be obtained rapidly. Results for a 25 m shaped Cassegrain antenna demonstrate that the adjustment of the subreflector to the optimal position as determined by the proposed method can improve the EM performance effectively.展开更多
The design of the Qitai 110 m Radio Telescope(QTT) with large aperture and very high working frequency(115 GHz) was investigated in Xinjiang, China. The results lead to a main reflector with high surface precision...The design of the Qitai 110 m Radio Telescope(QTT) with large aperture and very high working frequency(115 GHz) was investigated in Xinjiang, China. The results lead to a main reflector with high surface precision and high pointing precision. In this paper, the properties of active surface adjustment in a deformed parabolic reflector antenna are analyzed. To assure the performance of large reflector antennas such as gain and boresight, which can be obtained by utilizing an electromechanical coupling model, and satisfy them simultaneously, research on active surface adjustment applied to a new parabolic reflector as target surface has been done. Based on the initial position of actuators and the relationship between adjustment points and target points, a novel mathematical model and a program thatdirectly calculates the movements of actuators have been developed for guiding the active surface adjustment of large reflector antennas. This adjustment method is applied to an 8 m reflector antenna,in which we only consider gravity deformation. The results show that this method is more efficient in adjusting the surface and improving the working performance.展开更多
The angular method(AS)cannot be used in long-distance propagation because it produces severe numerical errors due to the sampling problem in the transfer function.Two ways can solve this problem in AS for long-distanc...The angular method(AS)cannot be used in long-distance propagation because it produces severe numerical errors due to the sampling problem in the transfer function.Two ways can solve this problem in AS for long-distance propagation.One is zero-padding to make sure that the calculation window is wide enough,but it leads to a huge calculation burden.The other is a method called band-limited angular spectrum(BLAS),in which the transfer function is truncated and results in that the calculation accuracy decreases as the propagation distance increases.In this paper,a new method called modified scaling angular spectrum(MSAS)to solve the problem for long-distance propagation is proposed.A scaling factor is introduced in MSAS so that the sampling interval of the input plane can be adjusted arbitrarily unlike AS whose sampling interval is restricted by the detector’s pixel size.The sampling interval of the input plane is larger than the detector’s pixel size so the size of calculation window suitable for long-distance field propagation in the input plane is smaller than the size of the calculation window required by the zero-padding.Therefore,the method reduces the calculation redundancy and improves the calculation speed.The results from simulations and experiments show that MSAS has a good signal-to-noise ratio(SNR),and the calculation accuracy of MSAS is better than BLAS.展开更多
基金supported by the National Natural Science Foundation of China(NSFC,Grant No.U1931137)the National Key Basic Research Program of China(2018YFA0404702)。
文摘Dual-reflector antennas are widely used in astronomical observations and satellite communication.Structural deformations of the reflectors for radio telescopes are inevitable in outside working conditions due to exterior environment loads,which will cause distortion in the surface of the primary reflector and displacement of the subreflector,then lead to gain degradation and misalignment.In this paper,the influence and correction of misalignment in a dual-reflector antenna have been studied.From the perspective of wavefront aberration,a method is proposed to correct the wavefront primary aberration by adjusting the subreflector position.The characteristics of wavefront errors caused by structural deformation of the reflector have been analyzed,and relationships between the position motions of the subreflector and the Seidel wavefront aberrations are derived.The adjustment quantities of the subreflector are also derived.The results show the appropriate positional change of the subreflector in the lateral and axial directions can effectively correct the effects of the tilt and defocus in the primary aberrations caused by antenna structural deformations.
基金supported by the National Key Basic Research Program of China (2015CB857100)the Chinese Academy of Sciences (CAS) "Light of West China" Program (2017-XBQNXZB-021)+2 种基金the National Natural Science Foundation of China (Nos. 51805399 and U1737211)the Natural Science Foundation of Shanxi Province (No. 2018JZ500)supported by the Operation, Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments, budgeted from the Ministry of Finance of China (MOF) and administrated by CAS
文摘A new method based on the parameters iteration technique has been developed to determine the optimal subreflector position for shaped Cassegrain antennas, that are distorted by gravity, to improve their electromagnetic(EM) performance. Both the features of shaped surface and the relationship between optical path difference(OPD) and far field beam pattern are employed. By describing the shaped dualreflector surface as a standard discrete parabola set, we can utilize the optical features of the standard Cassegrain system in the classical OPD relationship. Then, the actual far field beam pattern is expressed as the synthesis of ideal beam and error beam by decomposing subreflector adjustment parameters using a mechanical-electromagnetic-field-coupling-model(MEFCM). Furthermore, a numerical method for determining optimal subreflector position is presented. The proposed method is based on the iteration technique of subreflector adjustment parameters, and the optimal far field pattern is used for the iteration. The numerical solution of optimal adjustment parameters can be obtained rapidly. Results for a 25 m shaped Cassegrain antenna demonstrate that the adjustment of the subreflector to the optimal position as determined by the proposed method can improve the EM performance effectively.
基金supported by the National Basic Research Program of China(973 Program)(Grant No.2015CB857100)the National Natural Science Foundation of China(Grant Nos.51522507,51475349 and 51490660)+1 种基金the Youth Science and Technology Star Project of Shaanxi Province(Grant No.2016KJXX-06)the National 111 Project(Grant No.B14042)
文摘The design of the Qitai 110 m Radio Telescope(QTT) with large aperture and very high working frequency(115 GHz) was investigated in Xinjiang, China. The results lead to a main reflector with high surface precision and high pointing precision. In this paper, the properties of active surface adjustment in a deformed parabolic reflector antenna are analyzed. To assure the performance of large reflector antennas such as gain and boresight, which can be obtained by utilizing an electromechanical coupling model, and satisfy them simultaneously, research on active surface adjustment applied to a new parabolic reflector as target surface has been done. Based on the initial position of actuators and the relationship between adjustment points and target points, a novel mathematical model and a program thatdirectly calculates the movements of actuators have been developed for guiding the active surface adjustment of large reflector antennas. This adjustment method is applied to an 8 m reflector antenna,in which we only consider gravity deformation. The results show that this method is more efficient in adjusting the surface and improving the working performance.
基金Project supported by the National Natural Science Foundation of China(Grant No.61705254)the Key Research and Development Program of Shaanxi Province of China(Grant No.2020GY-114).
文摘The angular method(AS)cannot be used in long-distance propagation because it produces severe numerical errors due to the sampling problem in the transfer function.Two ways can solve this problem in AS for long-distance propagation.One is zero-padding to make sure that the calculation window is wide enough,but it leads to a huge calculation burden.The other is a method called band-limited angular spectrum(BLAS),in which the transfer function is truncated and results in that the calculation accuracy decreases as the propagation distance increases.In this paper,a new method called modified scaling angular spectrum(MSAS)to solve the problem for long-distance propagation is proposed.A scaling factor is introduced in MSAS so that the sampling interval of the input plane can be adjusted arbitrarily unlike AS whose sampling interval is restricted by the detector’s pixel size.The sampling interval of the input plane is larger than the detector’s pixel size so the size of calculation window suitable for long-distance field propagation in the input plane is smaller than the size of the calculation window required by the zero-padding.Therefore,the method reduces the calculation redundancy and improves the calculation speed.The results from simulations and experiments show that MSAS has a good signal-to-noise ratio(SNR),and the calculation accuracy of MSAS is better than BLAS.