A Tri-Band Omnidirectional Shark-Fin Antenna for Vehicle Applications: Design and Analysis.

In this paper, a tri-band omnidirectional shark-fin antenna for vehicular communications is proposed, which can cover three operating bands: Ultra High Frequency (UHF, 400-470 MHz), LTE Band 5 (824.2-879.2 MHz), and LTE-1800 (1765-1880 MHz). The antenna integrates a central UHF monopole and a pair of symmetric printed radiating elements within a compact shark-fin radome. The printed elements excite independent resonant modes in each band by using T-shaped and I-shaped radiating branches; broadband matching and balanced excitation are realized through a tapered impedance transformation network; and a dual-band array configuration is adopted to improve gain and stabilize radiation patterns. The monopole and printed elements form a collaborative array in a limited space, achieving structural miniaturization while obtaining good isolation and omnidirectional radiation characteristics. Results show that the peak gain of the antenna is 2.3 dBi in the UHF band and 7.2 dBi in the LTE-1800 band, and the isolation is better than 10 dB. The measured results are consistent with simulations, verifying the feasibility of the proposed design for application in high-performance vehicular communication systems.