Design of a Tapered Balun for Broadband Arrays With Closely Spaced Elements

In this letter, a broadband tapered balun array is proposed for the feeding of a broadband array with elements placed very closely to each other. Due to the tight space left in the array for designing the feeding structure, an extended and staggered structure of the tapered baluns is adopted. The balun array is designed, fabricated, and measured. Simulated results and measured results show that the balun array can be used to achieve a very broadband property.