A Study Of Dual-sleeve Broadband Antenna Based On End-loaded Technology

This paper proceed from achieving excellent impedance matching and broadband at the same time, based on the sleeve antenna and the basic theory of the asymmetric dipole antenna and impedance transformation, introducing the idea of cancellation, designed a novel of broadband dual-sleeve omnidirectional antenna based on end-loaded technology. Due to the particularity of the antenna’s structure, making the antenna composed by a double fed asymmetric dipole.The working frequency of the antenna is from 57 MHZ to 103 MHZ, in this range, the antenna’s VSWR is less than 1.5(i.e., S11< 13.98 dB), namely the relative bandwidth of the antenna is 57.5% under such a high VSWR requirement, and the impedance bandwidth is1.81:1. The measured results show that the gain is more than 2 dB in the working frequency the antenna. Results also show that the S11, E plane and H plane direction graph of the model antenna with resonance frequency 60 MHZ and 85 MHZ are in good agreement with the simulation results, thus proves the feasibility and effectiveness of the antenna.In this paper, we discussed the end load parts of the broadband dual-sleeve omnidirectional antenna based on end-loaded technology, and particularly discussed the influence of the two end load parts to the antenna’s S11 respectively. Furthermore, the equivalent circuit model of the broadband dual-sleeve antenna based on end-loaded technology is proposed in this paper, using MATLAB to solve the input impedance, and get the S11. Results show that the S11 obtained from the model matches well with the S11 obtained by CST simulation, which can provide a new method for the building of the traditional sleeve antenna’s theory model, thus solved the problem that traditional sleeve antenna’s theory solution can’t agree well with the actual results.In the same time, based on the theory that is proposed in this paper, the antenna with working frequency 0.8GHz-2.7GHz is proposed, and it’s Omni-directional in the H-plane, and the gain is mostly more than 2dB. This antenna proves the effectiveness of the broadband dual-sleeve antenna based on end-loaded technology, and this antenna’s working frequency covers the 2G, 3G, 4G, so it can be used as village’s base station antenna, thus will solve the problem that the traditional base station antenna can’t cover a wide band frequency so it needs several antennas, and they disturb each other, besides, they would occupy more area.All in all, this paper proposed a new broadband dual-sleeve antenna based on end-loaded technology, which breaks traditional sleeve antenna’s limitation that its impedance bandwidth is not wide enough with excellent impedance match. By introducing the idea of cancellation, greatly expand the impedance bandwidth of the antenna with excellent impedance match(VSWR < 1.5), thus provides a new train of thought for broadband antenna’s design. At the same time, this paper puts forward the equivalent circuit model of this new broadband dual-sleeve antenna based on end-loaded technology, providing a new train of thought for theory model’s building of traditional sleeve antenna, so as to solve the problem that traditional sleeve antenna’s theory solution can’t agrees well with the actual result, which has a great significance.