On the other hand, a discone antenna [16, 17] is wideband and can be considered as a special case of biconical antennas .
If a discone antenna structure is applied to the UHF band directly, its features cannot be maintained: due to the relatively long wavelength of the UHF band, the height of a discone antenna is large which makes the antenna difficult to be conformal and of low-profile [22-25].
In , a lumped-element loading method was used to widen the frequency bandwidth and the resultant discone antenna was made to have a height of less than 0.
The antenna is built on a modification of a discone antenna that is flattened but with additions of a back cavity, a short-circuiting structure and a two-plate top structure.
It is built on a discone antenna that is flattened but with three major additions: (1) an open-end cylindrical cavity that surrounds the cone, (2) a short-circuiting structure that is made of an open-ended cylindrical wall with its upper edge connected to the top circular plate of the discone antenna through three solid metal angles placed 120[degrees] apart, and (3) a circular metal plate added above the top circular metal plate with supporting metal posts in between the two plates (forming a parallel plate structure above the top of the cone).
In other words, the proposed antenna has the discone antenna as its basic part but with a large cone angle to reduce the height.
The open-end cylindrical wall and the three angle metals form the short-circuiting structure that provides short-circuited current paths between the top circular plate of the discone antenna and the ground or the bottom of the cone (see Figure 1(b)).
The two-plate top structure is composed of the two parallel plates, one being the circular top plate of the discone antenna and another being the one above it; the two plates are connected by several thin metal posts (see Figure 1).