Research And Application Of Ultra-wideband Circularly Polarized Antenna Beam Broadening Technology

Ultra-wideband circularly polarized antennas have become the era of the military and civilian frontiers due to their extremely wide frequency band coverage and flexible low-loss polarization matching.An ultra-wideband antenna with broad beam-width could expand the application scenarios of ultra-wideband circularly polarized antennas in various fields.Therefore,various beam broadening techniques for different ultra-wideband circularly polarized antennas are deeply studied in this paper and some good designs are analyzed in detail:The first part focuses on the ultra-wideband circular polarization technology of microstrip antennas and several beam-broaden techniques in the field.In the second part,the effect of a backed-cavity on the beam of the planar spiral antenna has been explored.A novel conical-ladder hybrid cavity is proposed,which is designed to direct the reflected wave of the backward radiation and to be superimposed with the radiation at the low elevation angle,sacrificing the beam-width in a part of the azimuth range for the antenna to achieve beam-broaden effect in another part of the azimuth range.And the advantage is obvious.In the third part,the beam broadening technique of an ultra-wideband circularly polarized microstrip antenna is studied.First,an ultra-wideband four-fed octagonal-shaped microstrip patch with circular polarization is designed.Then,two different metal-derived structures are respectively loaded on the ground.The beam-width is broadened due to the parasitic radiation they generated.And the antenna is miniaturized,too.Finally,the flat lens dielectric cover and the parasitic dipole are taken separately to complement each other,and the beam-width is further broadened without affecting other performances.In the fourth part,a broad-beam receiving antenna front end working on the X-band with its polarization reconfigurable is designed for the missile-borne wireless communication system.It can receive left-handed and right-hand circularly polarized signals at different time.The entire receiving front end was processed and measured,it performs well and stable.Then,according to the derivative demand of the missile-borne receiving front end,the feeding network was improved by using LTCC technology,which greatly reduced the size and the risk caused by processing and amplitude and phase balance.