Research On Multifunctional,Miniaturized,Low Profile,Vertically Polarized,End-Fire Antennas

Low profile vertically polarization end-fire antennas are very promising in airborne,vehicle,missile-borne communication and radar system.With the mature development of the modern integrated circuit technology,wireless communication and radar system towards miniaturization and compactness.Therefore,the miniaturization of antennas has also become an inevitable trend,especially in the fields of defense and military.A series of high-tech equipment,such as Beidou navigation systems and stealth fighter,has higher requirements for the miniaturization and compactness of antennas.It is still extremely challenging to realize the miniaturized design of vertically polarized end-fire antenna under the condition of low profile.Based on this background,some research is done on the reduction of profile and size of vertical polarization end-fire antennas in this thesis.And on this basis,the flexible and reconfigurable performance of antennas are extended to make antennas more intelligent.Two miniaturized low-profile vertically polarized end-fired antennas are designed:1.A miniaturized low profile vertically polarized end-fire antenna with flexible conformal characteristics is proposed.Using the near-field resonant parasitic(NFRP)technology,employing the interdigital structure,and etching a C-shaped slot by steps,the miniaturized total size is obtained,and based on the Yagi antenna principle,the end-fire radiation of the antenna is achieved.Finally,the antenna maintains good end-fire radiation and high radiation efficiency(>96%)even when the electrical size parameter ka is only 0.82 and the profile height is only 0.035?_L(?_L is the free-space wavelength corresponding to the lowest operating frequency in the working frequency band).Moreover,the antenna exhibited stable radiation performance characteristics when it was conformally mounted on conducting cylinders with different radii.A6-element array that encircles a conducting cylinder with only 50mm radius was simulated,fabricated and measured.The measured results indicated that the proposed antenna provides an impedance bandwidth of?8.2%and a peak realized gain of 6.4d Bi.The half-power beam width in H-plane higher than 60°,which allows the array to have the beam-scanning ability that dynamically covers all forward directions around the cylinder.2.A miniaturized low profile vertically polarized end-fire antenna with pattern reconfigurability is proposed.The antenna consists of three identical top-loaded folded monopoles and a simple reconfigurable feed structure.The antenna has three dynamic end-fire states facilitated with only three p-i-n diodes.The half-power beamwidth in H-plane in each state covers more than 120°,and hence,it can achieve beam scanning that covers the entire azimuth plane by dynamically adjusting three states.The antenna profile height and transverse size are,respectively,only 0.048?₀ and 0.1?₀².Measured and simulated results demonstrate that the antenna exhibits a?11%fractional impedance bandwidth(FBW),and a?6.6d Bi peak realized gain in three pattern-reconfigurable states.This pattern-reconfigurable antenna has potential applications in space-limited base stations and compact intelligent transportation systems.