An Aperture-Shared Vehicular Antenna With Large Frequency Ratio and Pattern Diversity for Future 5G Millimeter-Wave and DSRC Applications

A vehicular antenna with diverse radiation patterns is proposed for both the dedicated short range communications (DSRC) and the fifth-generation (5G) millimeter-wave (MMW) communications. The proposed antenna mainly comprised a 2 × 2 MMW subarray, an 8-element DSRC subarray and a corresponding 5-port feeding network. The radiating patches of the MMW subarray are excited by two pairs of coaxial-to-substrate integrated waveguide (SIW) transition (CST) feeding networks that are comprised of two 3-dB couplers, two 90<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>-phase shifters, and four power dividers (PDs), which provide in-phase and differential-phase output signals to achieve single-beam and conical-beam radiation patterns. On the other hand, the 8 monopoles of the DSRC subarray arranged around the aforementioned MMW radiator are excited by a coaxial-to-SIW-to-coaxial transition (CSCT) feeding network that includes a 1-to-4 SIW PD and four 1-to-2 microstrip PDs to form an omni-directional radiation and achieve a large frequency ratio (LFR). Measured results indicate that wide bandwidths of 15.44% (24.14-28.18 GHz), 16.09% (24.29-28.54 GHz), 15.01% (23.85-27.72 GHz), and 14.29% (24.05-27.75 GHz) with corresponding high peak gains of 10.97<inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>1.03 dBi, 11.71<inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>1.32 dBi, 10.84<inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>1.00 dBi, and 11.29<inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>1.28 dBi are obtained by the four MMW subarray ports, while a bandwidth of 11.40% (5.46-6.12 GHz) with an azimuth-plane gain of 0.64 dBi and a peak gain of 4.29<inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula>0.19 dBi for the DSRC subarray port are also obtained. Besides, low cross-polarization (X-pol) levels of −24 dB and −27 dB are achieved for the two subarrays, respectively.