Design Of Multi-band Wide-beam Navigation Antenna

With the development of Beidou navigation satellite system(BDS),it becomes an important part of China aerospace industry.As the key equipment for receiving and transmitting signals,the antenna has a great influence on the efficiency of BDS.The receiving grounded terminal equipment is required to cover not only roof space radiation pattern but also the equator direction of the low elevation satellite signal.More working frequencies can reduce the complexity of the antenna and optimize the working space of the whole machine.Nowadays,circularly polarized antenna is widely used in this field,because of its depolarization and anti-multipath effect.Therefore,circularly polarized antennas with multi-frequency and wide beam performance is a hotspot in satellite navigation.In this thesis,microstrip antenna for BDS B1 frequency(the antenna gain about 6.7dBic,half power beam width about 73�)is taken as an example based on the research background.In the third chapter,the characteristics of broadband and wide beam are studied respectively.By loading lumped inductors and capacitors on the feeding network,composite left/right handed transmission line is introduced to improve the impedance matching of this antenna,and the relative bandwidth of the proposed antenna is up to 45%.By loading metal back cavity,the half power beam width is improved from 73� to 90�.In addition,the sequential rotation feeding technique and the second-order Wilkinson power divider are used to improve the number of feeding points,it is aimed to improve the stability of the phase center.The fourth chapter summarizes the research methods of the third one,and the new proposed antenna should have the characteristics of broadband and wide beam.The feeding network is composed of a 180� phase shifter and two 90� power dividers and lumped inductors and capacitors.The signal is exported by four linear polarized waves with equal amplitude but 90� in such a wide operating band and the operating bandwidth of the proposed antenna is up to 60%.In order to simplify the antenna structure,four ?-shaped parasitic branches rather than metal back cavity are conducted to widen their 3dB beamwidths which are raised to 100� at representative navigation frequencies.The far field direction is superimposed by the microstrip antenna and dipole antenna.The stability of the lowfrequency phase center is less than 1%,and the stability of the high frequency phase center is less than 5%.This antenna can be widely used in satellite navigation systems.