Analysis of common‐mode effects in a dual‐polarized planar connected‐array antenna

An analysis is presented of the efficiency of a dual‐polarized planar connected‐array antenna, with particular reference to possible use in wideband focal‐plane‐array applications. The modeling approach is described, and the results of different numerical techniques are compared. The analysis includes the effects of transmission lines used to load the array at a groundplane. Different types of loading are compared including optimum single‐ended loading and optimum differential‐mode loading with short‐circuit and open‐circuit common‐mode terminations. The results indicate that high efficiency over useful bandwidths should be possible. In the case of differential‐mode loading, the efficiency may be reduced at certain frequencies due to resonances of common‐mode currents on the transmission lines. The current distributions on the array are analysed, and observations are made which may be useful for modified designs.