Design Of Beam-Switchable Cylindrical Conformal Antenna Array And Feeding Circuit

In recent years,with the rapid development of mobile communication technology,the number of mobile users has increased sharply,and the problem of spectrum resources shortage has become more and more serious.To solve this problem,low-cost,high-efficiency beam-switchable antennas are widely used in wireless communication systems.This kind of antenna can switch the appropriate beam to work according to the different requirements of the user’s location and radiation coverage.However,the current planar structure has problems such as difficulty in achieving omni-directional beam coverage and difficulty in erection.The cylindrical conformal beam-switchable antenna can make up for these shortcomings.Thus,two cylindrical conformal beam-switchable antennas are designed in this thesis,the main achievements are as follows:（1）A cylindrical conformal dielectric resonator array antenna based on aperture-coupled series-feeding approach is presented.The proposed design presents a tapered current amplitude distribution by using dielectric resonator element width gradation method,and low side-lobe level（SLL）characteristic can be obtained.The measured results show that the antenna is well matched in the working frequency range of 5.78 GHz～5.87 GHz(|S₁₁|<-10d B).At 5.8 GHz,the antenna offers a measured peak gain of 14.75 d Bi,and the vertical sidelobe level is-19.3 d B.The polarization discriminations of the array on the vertical and horizontal planes are greater than 25 d B.The measured results demonstrate that the proposed design can meet the requirement of applying for wireless communication system with curved surface.In addition,the isolation degree and the horizontal directivity patterns of 5 cylindrical conformal DRA array antennas are simulated,and the results show that the beam switching characteristics can be achieved.（2）A cylindrical conformal series-feeding microstrip array antenna is designed.The antenna is composed of 3 columns of 10-element microstrip series-fed antennas and a 3-way power divider.The current amplitude of the linear array meets the Chebyshev current distribution by using gradual patch method,so that the SLL characteristics of the antenna are improved.Besides,to improve gain of the array antenna,the proposed design uses the power divider to feed the three linear array antennas in same amplitude and phase.The measured results show that the 10-d B impedance bandwidth of the antenna is 90 MHz.The polarization discriminations of the array on the vertical and horizontal planes are greater than 35 d B.At the operating frequency of 5.8 GHz,a narrow beam radiation with a peak gain of 17.85 d Bi can be achieved,the SLL on vertical plane is-21.7 d B,and the SLL on horizontal plane is-22.4 d B.The proposed design can meet the target requirements of high gain,low SLL,and easy erection.The isolation degree and horizontal directivity patterns of 10 cylindrical conformal microstrip antenna arrays are simulated,and the results show that the beam switching characteristics can be achieved.3)In order to realize the beam-switchable characteristics based on the above two conformal array antennas,two feeding circuits are designed,including a 5-way power split switch feeding circuit and a 10-way switch feeding circuit.Among them,the 5-way power divider switch feeding circuit is composed of 5-way power divider and switch circuits,which can realize the separate excitation and simultaneous excitation of each preset antenna.The actual measurement results show that the output signal amplitude of each port of the circuit is about-10 d B.The 10-way switch feeding circuit is composed of 50Ωmicrostrip lines,microstrip power divider circuits and switching diodes,which can realize single output and arbitrary constant amplitude outputs.The actual measurement results show that the signal amplitude of the circuit is about-4.8 d B when the circuit is output with a single output,and the signal amplitude is about-8.5 d B when the two arbitrary outputs with equal amplitude.It proves that these two feeding circuits can meet the excitation requirements of the cylindrical conformal array antenna for the beam-switchable characteristics.