Dual-Band Dual-CP All-Metal Antenna With Large Signal Coverage and High Isolation Over Two Bands for Vehicular Communications

A dual-band dual-circularly polarized (CP) all-metal antenna is proposed in this paper for vehicular communications to realize large signal coverage and high isolation over two bands. On the one hand, by combining two rings of three-dimensional (3-D) L-shaped stubs and a circular patch, opposite CP radiations, i.e., right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP), can be achieved in lower and higher working frequency bands respectively, thus ensuring the isolation between different channels. On the other hand, both radiation patterns of two bands are conical-beam, i.e., omnidirectional, so as to realize large signal coverage, which is beneficial for vehicular communication especially when the car is moving or located on nonplanar plane. Besides, the proposed antenna is all-metal and can be easily manufactured by computer numerical control (CNC) machining technology. As such, it is expected to have higher power capacity than the conventional printed circuit board (PCB) structure. A prototype operating at 2.6 and 2.98 GHz is fabricated and measured, indicating that small frequency ratio between two operating bands can be realized. The proposed antenna is promisingly useful for application on vehicle to ensure simultaneous communications between different links without crosstalk, such as vehicle-to-satellite and vehicle-to-basestation communications.