On The Missile-borne Miniaturized Phased Array Antenna System And Special Circularly Polarized Antennas

The research works are made on the basis of scientific projects.Researches on the missile-borne miniaturized phased array antenna system and special circularly polarized antennas are presented in this dissertation.This dissertation consists of two main parts:First one presents the X-band missile-borne phased array antenna system,which achieves properties of broadband wide-angle scanning and miniaturization.The second part is concerned with the development of special circularly polarized antennas,including two unit rotation circular polarized array antennas and two planar endfire circularly polarized antennas.The author's major contributions are outlined as follows:1.X-band broadband wide-angle scanning missile-borne phased array antenna systemAccording to the requirements of broadband wide-angle scanning,limited size,and fast beam switching,the tile construction is employed to develop the system.From top to bottom,the system consists of a 6×6 Vivaldi antenna array,the beam controller with FPGA as the main chip,18 one-to-two T-shaped power dividers,the 18-square-to-round,and the transceiver switch.The system realizes broadband wide-angle scanning and fast beam switching under the limited platform size.Based on the study,the prototypes of all the parts in the system are fabricated and assembled.Various electrical properties of the system is measured.The measured results reveal that within the required operating bandwidth from f _L to f_H,the 6×6 linearly polarized phased array system has a VSWR of less than 2.5 under all scanning states.7 scannning beam positions are achieved in both the elevation plane and the azimuth plane.Under all the scanning states,SLL are less than-8.0dB,gains are greater than 5.7 d B,and the 3-dB beamwidths are less than 31°.The proposed phased array has a wide scanning range of±?_s.The beam switching is less than 1?s.The whole size of the system is?136 mm×83 mm.The interface form of the microwave signal is SMA,and the interface form of the control and power signals is J30J.All of the resuls meet the design requirements.2.Unit rotation circularly polarized array antennaTwo unit rotation circularly polarized array antenna are studied.One is the unit rotation circularly polarized array antenna without phase compensation,which can generate beam scanning.The other one is the unit rotation circularly polarized array antenna with phase compensation,which can suppress the cross polarization.For some circularly polarized antennas,there is a linear relation between the phases of their far fields and the azimuth angle,and the amplitudes are almost constant with the variation of the azimuth angle.If such an antenna is rotated around its own phase center by certain degrees,there is a phase difference between the electric far fields generated by the antenna rotated before and after at a fixed point.Then a linear array with such sequentially rotated CP antennas as elements can generate beam scanning.First,a linear array with 4 sequentially rotated planar spiral antennas as elements is designed to validate the proposed mechanism.The proposed array consists of spirals,bluns,and cavities.The planar spiral antenna is loaded with two 50 ohm resistors to absorb the reflected current at the end of its two arms to improve the propertis at lower frequencies and realize miniaturization.For easy fabrication and low cost,the eflection cavity is formed with the stepped metallic vias in substrates and the conical cavity.On the basis of simulation,a prototype of the planar spiral array is fabricated and measured.The measured results reveal that the proposed array has a good beam scanning characteristic within X band.The axial ratios in the total scanning range are better than 3dB.The unit rotation circularly polarized beam scanning array antenna can generate beam scanning with different unit rotation angles.The beam scanning approach is validated.Second,a linear array with 4 planar spiral antennas sequentially rotated by 180°and a wideband out-of-phase power divider based on slotline T-junction is designed and fabricated.The simulated results reveal that within 8~12 GHz,the axial ratio of the unit rotation planar spiral array with phase compensation is less than 3 dB.Compared with the array without unit rotation and phase compensation,the proposed array has an improved cross polarization,which verifies the cross polarization suppression method.3.Planar endfire circularly polarized antennasTwo planar endfire circularly polarized antennas are developed.They are the printed endfire circularly polarized loop antenna and the endfire circularly polarized SIW horn antenna.The printed circularly polarized loop antenna is a quadrangle loop fed with microstrip line at one of its corner.The endfire circularly polarized SIW horn antenna is the combination of a classic SIW horn antenna and a printed dipole on the same substrate.In the printed circularly polarized loop antenna,the microstrip line part mainly provides the vertical polarization,and the horizontal polarization is generated by the loop part.The coaxial feed structure in the previous planar endfire circularly polarized antennas is not easy to be integrated with other microwave components on the same substrate.The microstrip line feed structure in the proposed loop antenna can solve this problem.The impedance bandwidth and the 3-dB AR bandwidth of the improved printed endfire circularly polarized loop antenna can both cover 8.0~12.5 GHz(43.9%),which improves the usable bandwidth of the previous planar endfire circularly polarized antennas.In the endfire circularly polarized SIW horn antenna,the classic SIW horn antenna mainly provides the vertical polarization,and the horizontal polarization is generated by the printed dipole.The simulated and measured results show that the proposed antenna radiates an end-fire RHCP CP beam parallel with its plane within 10.73~11.26 GHz.Whithin this band,the antenna has an AR of less than 3 dB and a CP gain between 4 dBic and 6 dBic.As a result,the designed endfire circularly polarized SIW horn antenna can be used in a windward platform with low section profile or a high-speed platform.