Effect of Facet Displacement on Radiation Field and Its Application for Panel Adjustment of Large Reflector Antenna

Large reflector antennas are widely used in radars, satellite communication, radio astronomy, and so on. The rapid developments in these fields have created demands for development of better performance and higher surface accuracy. However, low accuracy and low effi- ciency are the common disadvantages for traditional panel alignment and adjustment. In order to improve the surface accuracy of large reflector antenna, a new method is pre- sented to determinate panel adjustment values from far field pattern. Based on the method of Physical Optics （PO）, the effect of panel facet displacement on radiation field value is derived. Then the linear system is constructed between panel adjustment vector and far field pattern. Using the method of Singular Value Decomposition （SVD）, the adjustment value for all panel adjustors are obtained by solving the linear equations. An experiment is conducted on a 3.7 m reflector antenna with 12 segmented panels. The results of simulation and test are similar, which shows that the presented method is feasible. Moreover, thediscussion about validation shows that the method can be used for many cases of reflector shape. The proposed research provides the instruction to adjust surface panels efficiently and accurately.

Future Research Trend for Improving Large Reflector Antenna Service Performance

A large reflector antenna is one of the key components of a deep space telemetry track and command(TT&C)network,which is of great importance for human space activities,such as satellite communication,spaceflight,and deep space exploration[1].The main feature of this antenna type is its large aperture and often it requires strict surface accuracy to ensure high gain and high pointing performance[2,3].There are two kinds of reflector antennas:non-fully movable antenna and fully steerable antenna.The Fivehundred-meter Aperture Spherical Radio Telescope in China is one representative non-fully movable antenna with a super large aperture and low operation frequency.The fully steerable reflector antennas worldwide can be further divided into four categories according to their aperture diameters and highest operation frequencies,as shown in Fig.1.Most of the antennas in Fig.1 can be found in Ref.[4]and the details are not presented here.Category 1 includes the traditional reflectors with large apertures and low operation frequencies.

Electromagnetic performance analysis of reflectorantennas with non-uniform errors along radius

Based on the works of Greve and Rahmat-Samii, theelectromagnetic （EM） performance of the reflector antenna withnon-uniform surface errors along radius is further addressed. Amathematical model is developed to describe the weighting functionfor the non-uniform surface errors along radius. Then, somediscussions on the peak gain loss （PGL） and the first sidelobelevel increase （SLLI） caused by the non-uniform surface errors arepresented and several significant radiation characteristics of thereflector with non-uniform errors are pointed out. Last, based onthe proposed model, the weighted root mean square （RMS） valueof the surface errors is produced to evaluate the EM performanceand several representative cases with different non-uniform errorsare presented with good results. Results show that the weightedRMS value should be taken into account for a better quality evaluationof the reflector surface.

Accurate Data Match and Call Method for the Thermal Compensation Database of the Reflector Antenna

The influence of thermal deformation on the performance of reflector antennas has become increasingly significant with the increasing aperture and working frequency.The use of a thermal compensation database is an efficient method to compensate for the deformation caused by the non-uniform temperature distribution.However,how to efficiently and accurately match and call the database remains as one of the tough challenges for the antenna thermal compensation system to achieve real time compensation.Therefore,this study proposes a data match and call method for the thermal compensation database of the reflector antenna,matching the database from three aspects:the overall rms match of temperature data,the similarity area match of each data sample,and the key area match of key structural positions.The validation of this method is demonstrated in an example.The difference between the pointing adjustment amount calculated by the matched data and the collected data was found to be less than 1",which satisfied the requirements of practical engineering,thus achieving real-time thermal compensation of the antenna.