| Global Navigation Satellite Systems(Global Navigation Satellite System,GNSS)has been widely used in various fields.The receiver antenna of satellite navigation system should have good omnidirectional reception characteristics,receive circular polarization signals,and meet the needs of satellite navigation frequency band.In general,the bandwidth of the receiver antenna only needs to meet the designed satellite navigation frequency band,but in order to improve the universality,multi-frequency antenna is generally used to cover multiple frequency bands.But some bands tend to be clustered together,it's hard to use a multi-frequency antenna to cover these bands one by one,so a broadband antenna should be used to cover these frequency bands.For these requirements,the quadrifilar helix antenna(QHA)has a good omnidirectional reception characteristic,receiving circular polarized waves,large working bandwidth.However,the QHA has a disadvantage that is the contradiction between the bandwidth and the size.When the antenna size is reduced,the impedance matching of the antenna will become worse,resulting in the reduction of the bandwidth.Based on the standard QHA,this paper combined with a variety of antenna structure design methods,mainly aimed at the miniaturization and broadband design of the QHA.The main work of the paper is divided into the following three points:(1)A design method of miniaturized wideband QHA is presented,which USES three improved techniques.First,the antenna arms are folded twice to reduce the size.Second,dielectric loading with a cylinder which relative permittivity is 9.5 to reduce electrical length.Finally,a short-circuit probe is added to the second bend of the antenna arm to adjust the impedance matching and expands the bandwidth.The size of the designed QHA was reduced and the working bandwidth of 100 MHz was reserved.Compared with the standard QHA,the axial length of the QHA is reduced by 77.1%,and the diameter of the antenna is miniaturized by 62.5%,This antenna has wider bandwidth than other smaller antennae,and is more compact than the other antennae with larger bandwidth.(2)Based on this design method,the working frequency of the antenna is designed by adjusting the inner and outer diameter of the dielectric cylinder.The working frequency of the antenna can be adjusted between 1.2 and 1.8 GHz without changing the size of other structures,and the bandwidth of about 100 MHz can be guaranteed.This method only needs to prepare the antenna arm,and then replace different replacement dielectric cylinder,can get the antenna of different operating frequency.According to this method,two antennas with center frequency of 1.227 GHz and 1.575 GHz were designed to meet the needs of satellite navigation system,which successfully covered the densely distributed band nearby.(3)Considering the limitation of experimental materials,this paper redesigned the antenna with center frequency of 1.500 GHz for physical production and testing to verify the correctness of the whole design.For this reason,the structure of the antenna is analyzed,and the antenna base plate and feed network are designed.The simulation results are basically the same. |
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