Investigation On The Key Technology Of The Folded Reflectarray Antennas

The reflectarray antenna combines the advantages of both the microstrip array antenna and reflector antenna,thus it becomes a hot topic during the past two decades.As one important type of reflectarray,the folded reflectarrays successfully decrease the entire antenna height to a half of the traditional reflectarrays by utilizing the polarizer grid.Therefore,depending on the low profile,the ease of fabrication and realization of multifunction,the folded reflectarrays have a huge potential to be applied in the SatCom-on-move system.According to the application background mentioned above,the key technology,the design method and the engineering realization aiming at the achievement of the large-angle beam-scanning,the employment of the integrated array feed and the function expansion of the circular polarization in the folded reflectarrays are researched systematically in this thesis.Therefore,the main contents of the thesis include as follow:1.Study on the receiving efficiency the folded relfectarray.The basic theoretical model of the folded reflectarray is built up.The related major factors,which effect the antenna efficiency of the folded relfectarray,are analyzed in detail.The receiving efficiency of the main reflecting face in the floded reflectarray is discussed with emphasis through using the Fourier Transform in the spectral domain.And the relationship between the receiving efficiency and the realizable beam-scanning angle of the unit cell is deduced.2.By employing the low-k dielectric overlayer,a design method of the dual-linear-polarized couple-feed microstrip slot-type unit cell for the wide-angle beam-scanning folded reflectarray is presented.The designs of the unit cells in C-band and Ka-band are accomplished.By using the commercial software,the performance of the proposed unit cells is characterized by the simulated results of the reflection coefficient of the the feed ports,the coupling coefficient between the feed ports,the transmission coefficient between the feed ports and floquet ports,the coupling coefficient between the floquet ports of the unit cell models under the periodical condition(master and slave boundary).According to the simulated results,the beam-scanning range from-60° to +60° in both E-plane and H-plane are achieved.3.Based on the PCB technology,a design method of the planar integrated primary feed for the folded reflectarray with the transmission-type polarization convertion manner.The design of the C-band integrated array feed is accomplished.The performance of the array feed and the horn feed is compared with each other through the simulated reflection coefficient and the radiation pattern and the prototype of proposed integrated array feed is characterized by the measured results.In addition,the design of the C-band and Ka-band folded reflectarray with the fixed beam angle including 0°,45° and 60° is accomplished.The wide-angle beam-scanning capability of the proposed folded relfectarrays is demonstrated by the simulated and measured results.4.By combining the classic meander-line polarizer and the polarizer grid,a design method of the circularly polarized folded reflectarray is presented.The design,fabrication and measurement of the C-band circularly polarized broadside folded reflectarray are accomplished.The tested results show that the axial ratio on the broadside direction of the proposed circularly polarized folded reflectarray is lower than 1.5 dB covering the frequencies from 4.75 GHz to 5.25 GHz.