VHF/UHF Ultrawideband Slim Monopole Antenna With Parasitic Loadings
Dongjie Qin, Baohua Sun, Rui Zhang
Abstract
A slim monopole antenna with novel parasitic loadings is presented in this letter. The proposed antenna consists of three metal strips, including a monopole strip and two parasitic strips on both sides, which is installed on a box that served as ground. Compared with traditional open sleeve monopole antennas, novel in-body structures are added to the three strips to achieve wider impedance and radiation pattern bandwidths. The in-body structures are composed of two parts, the inductive part (realized by etching a thin strip on the lower tip of the main strip) and the capacitive part (formed by adding a rectangular plate to the lower tip of the main strip). The prototype of the proposed antenna has been manufactured and measured. The bandwidth with VSWR ≤ 3:1 is 220–950 MHz (center frequency is 585 MHz), 4.3 octaves, which partly covers very high frequency (VHF) and ultrahigh frequency (UHF) bands. The gain is greater than −2.4 dBi. The antenna owns omnidirectional radiation patterns in the whole working band. With the thickness of the prototype being only 50 mm, it is suitable for the applications of backpacked radio stations and GSM communications.