ANALYSIS ON SUITABLE RADIATION-PATTERN OF CAR ANTENNA FOR MOBILE COMMUNICATIONS

The radiation pattern of a car antenna is evaluated with the power received by its antenna in mobile communication environments. In the evaluation, the horizontal radiation pattern is assumed to be omnidirectional; the vertical one is expressed in terms of the main beam direction theta-1 and the half-power beamwidth theta-BW. The received power is calculated from such a radiation pattern and an angular probability density distribution of wave arrival. The distribution is estimated using a propagation model to simulate radio propagation paths and surroundings of them in urban areas. The tendency of the estimated distribution is in good agreement with that of the measured one. It is clarified from the estimated results that the angular probability density distribution of wave arrival strongly depends on the street angle-psi. Since the received power calculated from the distribution also depends on psi, the minimum value (minimum received power) in the received power for psi = 5-degrees, 10-degrees, 15-degrees, ... 85-degrees is used to evaluate the radiation pattern. From the view that the radiation pattern for which the minimum received power is highest is suitable for mobile communications, it is revealed that theta-1 and theta-BW in the suitable radiation pattern of the car antenna are roughly 20-degrees and 15-degrees, respectively.