On The Conformal Missile-borne Antenna For End-fire Radiation And Low Profile Ultra-wideband Antenna

The research works of the thesis are made according to scientific research projects.First of all,the thesis describes the concepts,applications,the research status at home and abroad,and the background and significance of the topic selection of the designed antennas.Secondly,the research contents of this paper are discussed.Finally,the research results and research issues to be further studied are described.The major research can be divided into two sections:The first section is the design of two conformal missile-borne antennas for end-fire radiation,including conformal missile-borne linearly polarized antenna and conformal missile-borne circularly polarized antenna And the second section mainly aimes at the design and process of low profile Ultra-wideband antenna.The main contexts of the dissertation are outlined as follows:?1?Design of conformal missile-borne antennas for end-fire radiationAccording to the index of scientific research projects,we anlysis the technique difficulties how to produce radiation toward missile tail under the condition of the small distance between the antenna and the projectile body.Based on the above anlysis of difficulties,the schemes of conformal missile-borne linearly polarized antenna and conformal missile-borne circularly polarized antenna are determined.1)On the Conformal Missile-borne Antenna with Linely Polarized Character for End-fire Radiation.According to the requirements of limited size and end-fired radiation,we anlysis the technique difficulties.The resonant ring and reflective ring are selected to form Yagi ring antenna as the design scheme.The conformal missile-borne linearly polarized antenna dopts a resonant ring as a radiating element,so that the antenna radiates bidirectionally along the axis of the missile body.In order to suppress the interference of the back lobe to the adjacent region,the principle of Yagi antenna is used to construct a binary orientation loop array.By adjusting the size and spacing of the feeding loop and the reflection loop,the antenna produces end-fire radiation.Impedance matching can be adjusted by using the shorting pins and the gradation structures.ANSYS HFSS 13.0 simulation software is used to simulate the antenna.The simulation results show that the designed antenna has a voltage standing wave ratio of less than 1.2 in the operating frequency band?f₀±10MHz?,and the gain is greater than 7.3dB within a range of±15°beam,which meet the requirements of the project.The feasibility of the program is verified.2)On the Conformal Missile-borne Antenna with Circularly Polarized Character for End-fire Radiation.According to the requirements of limited size and end-fired radiation,we anlysis the technique difficulties.Two quaternion sub-arrays are selected for this antenna design.The sub-array select an inverted-F antenna as the array element,which is fed with sequential rotation feeding technology?0°,90°,180°,270°?.The sub-array realizes bidirectional circular polarization radiation and broadens the axial ratio bandwidth.But the gain of main polarization?right-hand circular polarization?don't meet the requirements.According to the end-fire array principle,the two sub-arrays are fed with equal amplitude and phase difference of 90°,and the distance between the two sub-arrays is about 1/4 wavelength,which can enhance the main polarization?right-hand circular polarization?and weaken the cross-polarization?left-handed Circular polarization?.The simulation results by HFSS software show that VSWR lower than 1.6 over 380–480MHz and axial ratio less than2.1dB can be accomplished.The gain is greater than 0.1dB within a range of±20°beam.The designed antenna meets the requirements of the project.?2?Design of low profile Ultra-wideband antenna with monopole-Like radiation characteristics.According to the requirements of the low profile of the antenna and the ultra-wideband,the technical difficulties are analyzed and the antenna scheme is determined.The antenna consists of a top-loading cap,an orthogonal cone-shaped radiation patch and a bending short-circuiting pin.In order to meet the low profile requirements,a top-loading cap is used to reduce the antenna profile.The folding paths are loaded,which extend the current path and improve the low frequency VSWR.Two tapered radiation patches on the crossed substrates can obtain good omni-directionality in the azimuth plane.However,in order to orthogonalize the two printed cone-shaped radiation patches,it is necessary to cut off each of the two dielectric plates by a complementary rectangular strip.But it has an influence on the distribution of the high-frequency current,so that the high-frequency standing wave coefficient increases.The method of loading the metalized vias in the center of the two dielectric plates can be used to turn on the high frequency current distribution,improve the high frequency standing wave coefficient,and further broaden the antenna bandwidth.The proposed antenna is simulated,fabricated and measured.The measured results show the antenna structure size is?74mm×26mm.Its working frequency band is 880-3800MHz.In the whole working frequency band,the pattern is circular in the azimuth plane and“?”in the elevation plane.The measure results are in good agreement with the simulation results,verifying that the project has engineering value.