Wideband Low-profile Dual-polarized Antenna

With the increasing number of communication users,the pressure on capacity of the original communication have doubled,and the traditional base station antenna(narrow bandwidth,large size,high profile)has been unable to meet the communication requirements.Therefore,the new generation of mobile communications is facing the contradictions of the continuous growth of users and the shortage of existing space resources.This leads to the developing trend of antenna toward broadband and miniaturization in the future.So the broadband and miniaturization are the core issues discussed in this paper.(1)In order to achieve broadband antenna design,a dual-polarized dipole antenna based on structural typing is designed.The antenna covers 1.63 ~ 2.97 GHz(S11 < 10 dB),and the isolation between two ports is greater than 22 dB in the frequency band.The radiation pattern is stable and the gain exceeds 7.77 dB.The wider bandwidth meets the design requirements of broadband base station antenna unit.(2)In order to optimize the broadband design of the antenna,a grid-type broadband dual-polarized antenna based on near-field coupling is designed.The principle of near-field coupling expanding antenna bandwidth is analyzed.The impedence matches well at 1.7GHz,2.2GHz and 2.7GHz in the whole band,which overcomes the problem of mid-frequency mismatch caused by the separation of two resonant frequency points.The relative bandwidth of impedence matching is 47.1%(1.67-2.70 GHz,S11 < 15 dB),the isolation is more than 23 dB with stable gain over 8.35 dB in the whole band.In order to enhance the near-field coupling effect,a planar cage broadband bipolar antenna is designed.The relative bandwidth of impedence matching is 55.0%(1.70-2.99 GHz,S11 < 15 dB),the isolation is more than 20 dB with stable gain over 8.3 dB in the whole band.(3)In order to realize the miniaturization design of broadband antenna,the broadband artificial magnetic conductor is designed to utilize in-phase reflector to reduce antenna profile in this paper.The equivalent circuit topology of broadband AMC structure is proposed.Compared with the traditional patch AMC structure,the in-phase bandwidth is extended from 7.5% to 61.5%.A broadband low profile dual-polarized dipole antenna based on broadband AMC is designed in this paper.The transverse dimension is reduced by the distributed capacitance inductance structure,the profile height is reduced by the principle of AMC in-phase reflection,and the broadband is realized by near-field coupling.The transverse dimension of the antenna is reduced by 22.7% and the profile of antenna is reduced by 50%.The relative bandwidth of impedence matching is 51.8%(1.70-2.84 GHz,S11 < 15 dB),the isolation is more than 30 dB with stable gain over 8.4 dB in the whole band.The simulated and measured result show a great agreement meeting the expected design targets.