Dual frequency array techniques experimental study

An experimental investigation of the twin slab dual frequency array element and low frequency element exciter is presented. Principal plane radiation patterns of the center element of a 23 element array are presented. It is shown that in the low frequency operating bands (4 GHz), the principal plane element patterns are synonymous with realized gain patterns reported previously. However, in the high frequency band (8 GHz), neither individual phase center patterns nor fully excited element patterns bear the normal relation to realized gain. In particular, array scan characteristics must be constructed by summing individual phase center pattern without the standard array factor exponential weighting. A novel coax-fed notch exciter for low frequency band operation has been developed empirically. The exciter provides greater than 20 dB band isolation over most of the 16 percent band centered at 8 GHz, and better than 1.9:1 VSWR over the 4 GHz band.