Figure 13 Grouping of the rings in the four subarrays. TABLE 3: Grouping of rings into different subarrays for broadband beamforming. therefore resulting in savings in array elements. The pro- posed compound ring structure has 4 operating frequency bands as listed in the second column of Table 3. The third column in the table shows the number of rings in each band and the fourth column is the number of elements in each ring for the frequency band considered. The grouping of the rings for different bands is shown in Figure 13. The minimum sep- aration between two rings is