| With the rapid development of wireless communication system,the main trends of system design are developing towards broadband,low cost,miniaturization and multi-function.For the purpose of reducing the system complexity,low profile microstrip patch antenna has become a hot research topic.In addition,with the rapid development of wireless communication system,satellite navigation and positioning technology has also developed rapidly.Global Positioning System(GPS)is a satellite-based navigation system,which has a wide application market.GPS system requires the antenna has the characteristics of wide-beam circular polarization.In this thesis,a wide-band low profile microstrip patch antenna and a high stable phase center PIFA antenna are investigated.The work is mainly divided into four parts:1.A broadband low profile microstrip patch antenna with double tuning impedance matching is designed.The antenna consists of a square copper patch,a ground plate and a step folded feeding network.The air layer is between the square patch and the ground plate.Using step folded probe as feeding structure,double tuning impedance matching can be generated to obtain wider working bandwidth.The antenna is fed by a 50 ? coaxial cable.The working principle of the antenna is analyzed from the point of view of equivalent circuit.The designed antenna model is also processed and measured.The results show that the algorithm is in good agreement with the simulation results.Relative impedance bandwidth(S11 < 10 d B)is 54.5%(1.60-2.80 GHz)and the antenna gain is about 7.7± 0.5 d Bi.At the same time,the Single-polarized antenna is changed to differential feeding and dual-polarized mode respectively.The simulation results show that the impedance bandwidth is not much different from that of single polarized antenna,but the cross-polarization level is lower.2.A single-fed single-layer linear polarization(LP)rotating square patch with omnidirectional radiation pattern is presented in this paper.The impedance bandwidth(|S11|<-10 d B)of the antenna are 40.7%(3.19-4.82 GHz).Meanwhile,the height of the antenna is 0.14?0(?0 is the free space wavelength corresponding the lowest frequency).The TM01 modes are excited in the two square patches.In the process of antenna design,two square patches are synthesized into a rotating patch,which forms the omnidirectional radiation characteristics.Using the proximity-fed,the dual-resonant point performances are realized.Moreover,the prototype processing and test of the antenna further show the effectiveness of the proposed structure.The proposed antenna has the characteristics of wide band and low profile,which makes it have great practical application value.3.The circularly polarized PIFA antenna system is designed.Firstly,the traditional PIFA antenna unit is analyzed,and then an 8-port feed circularly polarized antenna is analyzed.In order to simplify the feeding network design,the 8-port feed antenna is changed to 4-port feed antenna.The final antenna system is fed through four feed lines.The antenna radiator is printed on the upper layer of the circular FR4 dielectric plate with the shape of Chinese character "meter".The antenna radiator is connected to the floor through a metal short circuit column with a radius of 1.5 mm in the middle of the radiator.The metal ground and the feed network are respectively located on both sides of the substrate.In addition,a Wilkinson power divider is designed to output four 90° signals of equal amplitude and phase difference in sequence.The antenna is processed according to the simulation results.The impedance bandwidth of the antenna is 1.4-1.8 GHz and the axis ratio is less than 3 d B among 1.4-1.8 GHz.The maximum gain is about 7.52 d Bi at 1.56 GHz.4.A differentially fed dual-polarized PIFA antenna is designed.The antenna can meet|S11|<-10 d B in the 1.54GHz-1.62 GHz band,achieving a 5% impedance bandwidth.Due to the feed mode of differential feed,the differential isolation degree of the two antenna ports is greatly improved,and the simulation results show that the isolation degree is more than60 d B..At the same time,the gain of dual-polarized PIFA antenna floats within the operating frequency band in the range of 8.32 d Bi-8.45 d Bi,which is very stable.In addition,the radiation patterns of both polarized antennas have stable characteristics.Based on the dualpolarized PIFA antenna,an eight element dual polarized PIFA antenna array with equal amplitude and phase feeding is designed.From the analysis of the results,the antenna array meets |S11|<-10 d B in the 1.54GHz-1.62 GHz band,achieving 5% impedance bandwidth.Meanwhile,the radiation characteristics of the antenna maintain stable in the working band. |
PDF Full Text Request