Directional Antennas

The object of this paper is to develop analytical methods which are readily applicable to the general problems that arise in array design and to provide design curves that may be used without reference to the field theory underlying the problem. The cases of both driven and parasitic arrays have been treated. Where possible, the results have been tested by comparison with experimental results. The field and circuit conditions are treated for the case of multielement driven arrays. The effective impedance and the total radiated power, as well as the power radiated by each antenna, are determined. Expressions are given for the radiation patterns of the arrays. Examples are treated which show how these arrays are used to protect the service areas of other stations operating on the same frequency assignment. In the case of a single parasitic reflector, it is found that spacings less than a quarter wave length are desirable in both the transmitting and receiving case. It is seen that the parasitic antenna functions equally well as a director or a reflector. The case of an antenna parallel to an infinite sheet acting as a reflector is treated. It is shown that it is desirable to space the antenna very much less than a quarter wave length from the sheet. A method of measuring the mutual impedance between antennas is advanced. A systematic method of adjusting a complicated array is outlined.