“…3,4,[6][7][8][9][10] The vertical impedance transformer (balun) always has an essentially long length and contributes to the high profile antenna and causes problems in the assembly of the antenna. 11 Additionally, it makes the antenna structure nonplanar, complex, and large size, 12 conflicting with the requirements of the low-profile geometry which makes the entire antenna voluminous. This threedimensional feeding way is well investigated in the past.…”