Generation of unsymmetric sum and difference patterns

It is very common to generate sum and difference patterns from either discrete antennas or from arrays. In the first case, it is required to use a directional antenna and an omni directional antenna. Sum pattern is produced from the directional antenna and difference pattern is created by simultaneously exciting directional and omni-directional antennas. In the difference patterns so obtained a null exists in the bore sight direction although it is very deep. Moreover, the difference slopes are not optimal in terms of their heights. In the present work, an attempt is made to design an array to produce unsymmetric sum and difference patterns. The design involves the proposal of a typical amplitude distribution, which generates unsymmetric sum patterns. These patterns are converted into difference patterns again unsymmetric by introducing an additional phase of 180/spl deg/ to one half of the array.