PURPOSE: To reduce the interference degree between beams and also to increase the gain within each beam for a cluster feed multi-beam antenna, by deciding an optimum horn size and an optimum antenna opening diameter in accordance with the center space between beams to be radiated.
CONSTITUTION: A reflector antenna consists of a main reflector 22 and clusters 23 and 23'. These clusters are formed with a square array of (m×m) units of horns (m=3). Each horn has a square form of a side (d) together with an antenna opening diameter D and its offset angle θ0 and focal distance (f) respectively. Then the minimum center space is set 2ψ between two optional beams 27 and 27' among those to be radiated. Here the horn size (d) is decided so as to satisfy an equation d/λ=f/D.BDF.cos2(θ0/2), where λ and BDF show the wavelength and the coefficient of beam deflecting direction respectively. At the same time, the antenna diameter D is set to satisfy D/λ=m/2sinψ. In such a way, the side lobe of each beam can be set at a low level and at the same time the peripheral gain of each beam can be set at a high level.
YAMADA YOSHIFUSA
ITAMI YUUJI
