Antenna pattern compensation by optimization of phased array parameters for dynamic beam pattern control based on measured reflector shape
- Paper number
IAC-17,B2,1,13,x41687
- Year
2017
- Abstract
A very large aperture reflector antenna is the promising option for future mobile communication satellite for smaller user terminal antenna and output power. For enough electric performance of antenna, high accuracy of parabola reflector shape is required to avoid performance deterioration due to aberration. In the experiment of Engineering Testing Satellite VIII, offset and change of antenna pattern is found. The observed offset of beam center is larger than 100 km or 0.15 degree in some case (Satoh et al 2011). The change is considered due to the thermal deformation of reflector caused by the change of thermal environment and temperature of antenna structure in flexible structure. On board digital beam forming antenna with phased array can be used for modification of antenna beam performance and quality with adjustment of excitation parameters for phased array feed. If we can measure the reflector shape precisely in orbit, beam pattern and antenna performance can be compensated continuously with the updated excitation parameters optimized for the reflector shape measured every moment. Application of vision metrology for large onboard reflector in orbit is a challenge without precedents. By using simulation and trial measurement by using prototyping simulator, the feasibility of our proposal by four 4M pixels cameras with several meters separation is confirmed. In this report, the feasibility of beam pattern compensation by using accurately measured reflector shape is discussed. The reflector with 22 meters aperture and 37 elements feed is assumed for the beam pattern simulation for antenna. The linearly inclined distortion superimposed onto the ideal parabola shape is assumed as deformed reflector for the simulation. The beam pattern deteriorated with the parabola surface deformation is examined and the feasibility of beam pattern compensation by optimizing excitation amplitude and phase parameter for phased array feed is shown. This simulation shows that the deteriorated beam pattern can be compensated by using excitation parameter after optimization for measure reflector surface. Therefore, if reflector surface of communication satellite can be measured routinely in orbit, the antenna pattern can be compensated and maintain the high performance every moment. The feasibility of beam pattern compensation by using accurately measured reflector shape is confirmed with antenna pattern simulation for deformed parabola reflector.
- Abstract document
- Manuscript document
(absent)