# Low-Profile Dual-Polarized Antenna Integrated with Horn and Vivaldi Antenna in Millimeter-Wave Band
## 1 Introduction
The substrate-integrated waveguide technique can be used to confine the electromagnetic energy in the waveguide cavity by replacing the metal wall with a uniform array of metal columns. By using substrate-integrated waveguide technology, horn antennas can gain the advantages of easy integration and a low profile [22; 23; 24]. In [22], a dual-polarized end-fire antenna array is achieved by integrating dipoles on the SIW horns. A pair of dipoles produces HP, while SIW horn antennas radiate VP. The dual-polarized antenna can cover the 5G bands of N257 and N258 and achieve a maximum gain of 6.5 dBi for both polarizations. The isolation between two ports is higher than 15 dB. In [23], a dual-polarized antenna element is designed by combining an HP dipole and a VP \(H\)-plane horn antenna, and then a \(1\times 4\) antenna array is designed and fabricated. The impedance bandwidth where the \(|S_{11}|<-10\) dB for both polarizations is 24.4-29.5 GHz. In the operating band, the maximum gain is 16 dBi, with an isolation higher than 20 dB. An \(E\)-band SIW dual-polarized horn antenna with an orthomode transducer is proposed in [24]. An SIW section is adopted to excite the TE\({}_{10}\) mode and produce VP. The quasi-TEM mode is excited by a quasi-coaxial stripline, and HP is generated. Its impedance bandwidth lower than \(-10\) dB is from 83 to 87 GHz and achieves a maximum gain of 14 dBi for HP and 15.2 dBi for VP. The isolation between two polarizations is higher than 25 dB. In the abovementioned designs, in order to realize the dual polarization, the SIW horn antennas are always combined with complex feeding structures. This will increase the difficulty of fabrication and increase the antenna size. The isolation between two ports is also not good enough. Therefore, it is sufficient to provide a wide-band dual-polarized antenna with a simple radiation configuration and feeding structures as well as a good isolation performance. In this paper, a low-profile dual-polarized antenna is proposed by integrating a traditional Vivaldi antenna on the surface of the SIW \(H\)-plane horn antenna to realize dual polarizations. The Vivaldi antenna radiates VP electromagnetic waves, and the horn antenna radiates HP electromagnetic waves. A dielectric lens is loaded at the aperture of the horn antenna for better impedance matching and enhancing directivity. To improve the isolation between two ports, two different feeding structures are utilized to excite different ports. The proposed dual-polarized antenna is fabricated and measured, which achieves a \(-10\) dB impedance bandwidth from 20.94 GHz to 25.50 GHz for both polarizations. In the operating band, the antenna achieves a maximum gain of 8.2 dBi. The proposed dual-polarized antenna is suitable for 5G mm-wave communication. In Section 2, the design procedure of the dual-polarized antenna is illustrated, including the simulation results of the SIW horn antenna and Vivaldi antenna. In Section 3, parametric study is presented which is used to verify the influence of different parameters on antenna performance. The dual-polarized antenna is fabricated and tested. A comparison of the antenna simulation and test results as well as a comparison of this antenna with other published antennas are given in Section 4. Section 5 draws a conclusion of this work.