Research On Miniaturized Broadband Printed Dipole Antenna With Dual Polarization

With the rapid development of modern co mmunications, the fourth generation mobile communication system technology is relatively mature, and then the communication system has a higher demand for the electromagnetic characteristics of the antenna. As a communication system terminal, the antenna needs to have a wide impedance bandwidth, stable pattern and gain in working band, a low cross polarization level and a miniaturized size. O n the purpose of realizing profile miniaturization, broadband and dual-polarization of antenna, the planar crossed dipole antenna is studied in this paper.Firstly, a bowtie- like planar cross dipole antenna is designed.This antenna is composed by two same bowtie- like planar dipole antennas placed orthogonally. Based on traditional bowtie planar dipole antenna, each bowtie- like planar dipole antenna uses two isosceles trapezoids as arms, and every arm of the dipole antenna has a T-shaped slot and two symmetrical bending slots. Then a parasitic patch is loaded above the antenna, and the new resonant frequency is generated by introducing the parasitic structure to achieve the characteristic of broadband operation. The two ports' relative bandwidth of the bowtie- like cross dipole antenna are 55.7%, and the maximum gain of the antenna is 9.81 d B.In order to simplify the structure of antenna and the feed ing network, a C lover- like planar cross dipole antenna is presented. The antenna is composed by two same C lover- like planar dipole antennas placed orthogonally. One arm of each C lover-like dipole is printed on the front side of a dielectric substrate while the other arm is printed on the backside of the substrate. The C lover-like dipole is fed directly by coaxial line. Due to the coupling between two C lover- like dipole antennas orthogonally placed, a wide band is achieved. The antenna achieves a relative bandwidth of 49% of both ports, and a gain of 8.35 d B.Finally, based on the C lover- like planar cross dipole antenna mentioned before, the square patch AMC structure is loaded to miniaturize the antenna profile. Through the analysis of AMC surface impedance and reflection phase, some important parameters which have large impact on antenna are determined. Simulation results show the port 1 of antenna has a relative bandwidth of 57.5%, and port2 has a relative bandwidth of 54.7%. The gain is about 7.4d B. Compared with C lover-like planar cross dipole antenna without AMC structure, the bandwidth of antenna is increased about 27%, and approximately 50% height of antenna is reduced.The three antennas designed in this paper all have good front-to-back ratio,low cross polarization and stable gain to meet the requirements of modern communication systems for high performance antenna.