| 摘要 |
PURPOSE:To cause abrupt variation in directivity and to reduce adverse interference between base stations of the same frequency by arranging plural antenna units on a vertical line at a specific interval, and generating plural radiation beams by interference between radiant waves. CONSTITUTION:Two antenna units 6 and 6' are provided at an interval D. Electric power is distributed equally by a two way branching circuit 8 and fed. Their relative phase is adjusted by varying the length of a feeder 7 or 7'. The vertical surface directivity Ettheta of an antenna system is expressed by an equation I . In the equation, Etheta is the directivity of one antenna unit and D is the interval between antenna units; and lambda is wavelength and theta is the relative angle from the direction of a main beam. When the external angle thetaL of a service zone and the necessary amount LdB of attenuation are known, D is determined by an equation II. Assuming that thetaL=1.3 deg., L=10dB and lambda=333mm. (900MHz), D=6m. Namely, the necessary amount of interference suppression is obtained by arranging the antenna units at an interval of 6m. |
