BASE AND MOBILE STATION ANTENNAS FOR LAND MOBILE RADIO SYSTEMS

Design concepts and antenna features of Japanese mobile communication systems are clarified. The complete package of design tools used to structure the sidelobe characteristics of the low sidelobe tilted beam antenna (LSTA) is shown. This antenna is now in use as the base station antenna in Japan. It is shown that sidelobe levels of less than - 20 dB can be achieved in multipath propagation environments. This antenna can be simultaneously used for transmission and reception because of its very low intermodulation characteristics. Bench tests show the 7th order level is less than - 10 dB-mu even with a total antenna input of 160 watts. A new vehicular mounted antenna, the vertical space diversity antenna is examined. It is shown that a correlation coefficient of less than 0.5 can be achieved with an antenna spacing of 0.5 to 1 wavelength. A compact antenna whose total length is about 1.7 wavelengths is described. The latest Japanese portable phone antenna, a very compact diversity antenna employing a whip and an inverted F antenna, is tested. A correlation coefficient of about 0.2 is achieved with an antenna spacing of less than 0.1 wavelength. It is shown that radiation pattern differences between antennas, caused by mutual coupling, are the main cause of this small correlation coefficient.