| With the rapid development of air-space-ground integrated communication,the co-aperture antenna used in satellite communication system has an obvious advantage of improving the aperture utilization of satellite.Based on the theory of microstrip circularly polarized antenna,this thesis studies the design of circularly polarized and co-aperture antenna over the application background of satellite communication antenna,and the main contents are as follows:Firstly,a C-band microstrip circularly polarized antenna is proposed.On the basis of the traditional chamfered square circularly polarized microstrip antenna,the antenna uses the sequential rotated feeding technique to feed the four orthogonal microstrip patches with the same amplitude and phase delay of 90°.The results show that the antenna achieves an impedance bandwidth of 5.2% in the 4.87-5.13 GHz operating frequency band,the isolation between elements is more than 18 d B,and the axis ratio of the maximum radiation direction of the antenna in the target frequency band is less than 3 d B.Compared with the traditional circularly polarized antenna element,the antenna has wider impedance bandwidth and axial ratio bandwidth,and can be used as the higher band part of the common aperture design.Secondly,two S-band microstrip circularly polarized antennas are proposed.Both antennas adopt the orthogonal doubly-fed technology with close coupling of microstrip lines to feed the two orthogonal ports with equal amplitude and phase difference of 90°,respectively.Therefore it realizes the radiation of circularly polarized waves.The first antenna radiator is a circular patch,and the antenna achieves 2.8% impedance bandwidth in the 3.72-3.81 GHz working frequency band.The axial ratio of the maximum radiation direction of the antenna at the central frequency point is close to 0 d B,shows better impedance bandwidth and axial ratio bandwidth.The second antenna radiator is a cross patch.The results show that the working frequency band of the antenna is 2.78-2.80 GHz,and the axis ratio of the maximum radiation direction at the central frequency point is about 1.3 d B.Compared with the first antenna,this antenna has more compact structure and is easy to integrate with the higher band antenna.These two antennas are used as the lower band part of the co-aperture design.Thirdly,based on the above design of higher band circularly polarized antenna and two lower band circularly polarized antennas,two co-aperture circularly polarized antennas are proposed.The two antennas adopt interlaced structure,and the lower band antenna is embedded in the interspace of the higher band antenna to avoid the pattern distortion caused by mutual coupling.The first antenna embeds the lower band circular patch antenna into the central interspace of the higher band antenna to realize the co-aperture antenna,and its overall size is 72 mm×72 mm×1.574 mm.The results show that radiation patterns of the two antennas have little variation.The second antenna places the lower band cross patch in the cross interspace of the higher band antenna with an overall size of 63 mm×63 mm×1.574 mm,which is significantly smaller than the size of the last co-aperture antenna,while the far-field radiation characteristics of the two-band antenna remain unchanged compared with independent antenna units.Measured results show that the reflection coefficient of the antenna is less than-10 d B in the bands of 4.87-5.13 GHz and 2.495-2.505 GHz.The relative bandwidth of the higher band antenna the and lower band antenna is 8.1% and 0.4%.The axial ratio of the two antennas in the maximum radiation direction at the central frequency is less than 3 d B.Then,an array composed of the second co-aperture antenna is proposed,and its size is 1×5.The impedance characteristics and scanning characteristics of the antenna array are studied and analyzed. |
PDF Full Text Request