Bidirectional series fed slot array

Series fed antenna arrays are normally excited from only one end to maintain a high antenna efficiency. Antenna efficiency takes into account losses associated with non-uniform illumination efficiency, termination dissipation, and non-perfect conductors. The purpose of this paper is to show that a practical antenna structure utilizing a bidirectional feed can also be realized with high efficiency, The bidirectional feed has application in multiple beam systems where low weight is a design consideration. Typical applications are tactical radars and airborne radars. The technique described is an extension of a Soviet published paper which first discussed the concept in terms of an optimumized design. Unfortunately, the concept as described by the Soviets had several fundamental errors which precluded a practical hardware design. In this paper a correct treatment of the optimization concept is given, as well as the derivation of practical designs. The design of a bidirectional series slot array antenna having a cosine squared-on-a-pedestal aperture illumination is discussed. The patterns and efficiency of this antenna are compared to a conventional, single fed series array. The overall efficiency is expressed in terms of its constituent factors. Slot conductance calculations will be presented for the array to illustrate the design practicality. The work presented will also illustrate the procedure for realizing an arbitrary aperture illumination.