A Low-Profile Dual-Band Antenna With Different Polarization and Radiation Properties Over Two Bands for Vehicular Communications

A low-profile dual-band antenna with different polarization and radiation properties over two bands for vehicular communications is presented in this correspondence paper. The dual-band property is realized by employing a stacked-patch structure. By utilizing TM01 and TM10 modes of the truncated upper square patch, a unidirectional radiation pattern with circular polarization is achieved in the low band. By using TM01 and TM02 modes of the lower circular patch, omnidirectional radiation with linear polarization can be obtained in the high band. In order to widen the antenna bandwidth, a U-shaped slot is etched in the truncated square patch, and 12 conductive vias are inserted to short the circular patch to the ground plane. A fully functional prototype was developed and tested. The measurements show that an axial-ratio (AR) bandwidth (AR <= 3 dB) from 2.49 to 2.54 GHz and an impedance bandwidth (S-11 <= -10 dB) from 2.34 to 2.57 GHz are obtained in the low band and an impedance bandwidth (S-11 <= -10 dB) from 3.54 to 4.40 GHz is achieved in the high band. Unidirectional circular polarization and omnidirectional linear polarization are observed over two bands. In addition, the proposed antenna exhibits other advantages, such as low profile and high gain. With these characteristics, the proposed design is very suitable to be applied on a vehicle to meet both satellite and mobile communications.