Study On Directional High-gain Antenna Based On Tunnel Environment

Due to the interference of the tunnel environment on electromagnetic waves,directional high-gain antennas are needed to meet the complex terrain features.In this paper,a quasimicrostrip Yagi antenna that can be used for railway wireless communication is designed based on the relevant theory of Yagi antenna and printed dipole antenna,and its performance parameters such as bandwidth and gain are discussed.Based on this design,the gain is designed.Higher microstrip Yagi antennas,dual-polarization directional high-gain antennas and dual-band directional high-gain antennas.In order to improve the shortcomings of the large Yagi antenna and the relatively small gain of the microstrip printed antenna,a directional printed antenna designed for railway mobile communications was designed to work in the 900 MHz frequency band.The antenna is a combination of microstrip antenna and Yagi antenna.The microstrip antenna is a deformed printed dipole antenna with a T-shaped structure.The two vibrators are distributed on the upper side of the substrate at the same time,and a coupling branch structure is added between the two vibrators to improve the matching characteristics of the antenna.Add a dipole to the radiation direction of the printed dipole antenna,and add a reflector in the opposite direction to increase the antenna gain.The lead vibrator adopts a non-uniform Yagi antenna design,which achieves the purpose of widening the bandwidth.After simulation design,the average gain of the antenna in the 900MHz(885-935MHz)band is 9.6dBi,the relative bandwidth reaches 24%,the front-to-back ratio is greater than 20 dB,and the half-power beam width is controlled within 53°.Based on the design of the quasi-microstrip Yagi antenna,the microstrip Yagi antenna used in the 900 MHz frequency band was designed,and the number of directional vibrators was added.The antenna achieves a 28.5% relative bandwidth,a beam width within 40 °,and an average gain of 14.59 dBi through the non-uniform design of 11 dipoles and the fine-tuning of the printed dipole antenna structure.By orthogonally placing two pairs of linearly polarized microstrip Yagi antennas,the two ports are fed separately and packaged in the same radome,the dual-polarized high-gain radiation characteristics of the antenna are realized.In order to reduce the signal interference of the two antennas,a reasonable dislocation arrangement is adopted,and the microstrip structure is fine-tuned.The relative bandwidth of the dualpolarized antenna is 27.6%,the beam width is within 43 °,the dual-port isolation is greater than 26 dB,the average gain is 14.42 dBi,and the front-to-back ratio is greater than 20 dB,which effectively alleviates the signal fading problem in the tunnel.Based on the design theory of dipole antenna,a printed dipole antenna with microstrip balun structure is designed.And using its combination with Yagi antenna,a directional highgain antenna designed in the 1800 MHz frequency band was designed.The antenna has a relative bandwidth of 25.1%,a half-power beamwidth within 44 °,an average gain of 14.3dBi,and a front-to-back ratio greater than 18 dB.On the basis of this design,combined with the900 MHz frequency band microstrip Yagi antenna,two linearly polarized antennas are placed orthogonally,and the two ports are fed separately,encapsulated in the same radome,which realizes the antenna in the 900 MHz and 1800 MHz frequency bands.Dual frequency operation.The relative bandwidth of the dual-band antenna at low and high frequencies is 23.3% and 20%respectively,the average gain is 14.15 dBi and 13.95 dBi,and the half-power beam width is less than 41 ° and 45 °.It has high gain and directional capability,which can be effective Solve the problem of dual frequency working in the tunnel.