Research On Miniaturized Broadband Antennas For Direction Finding

In recent years,wireless positioning and direction finding technology has not only been in the military field,but also received extensive attention and application in the civilian field.Whether it is a monopulse direction finding system or an interferometer direction finding system,it is desirable that the antenna unit has ultra-wideband,miniaturization and light weight.In this paper,two wideband direction finding antennas with practical application value are designed based on wideband direction finding antenna theory and design scheme.In chapter 3,a four-arm spiral antenna based on monopulse direction finding is designed.Based on the multi-mode antenna theory,a microstrip tapered spiral feeder structure which can meet the input impedance of the antenna in two modes is adopted.Under the condition that the antenna radius is 52 mm and the profile height is 75 mm,the operating bandwidth of the antenna in 12 octaves in mode 1 and mode 2 is realized through simultaneously loading the resistor,the sine function zigzag arm,and the longitudinally extending arm.Finally,a multi-section metal reflective cavity that meets the broadband requirements is designed and loaded onto the antenna.The four-arm spiral antenna loaded with the reflective cavity achieves Active VSWR less than 2.5 and 2 in the 1GHz?2GHz and 2GHz?12GHz frequency bands,respectively.The mode 1 beam satisfy the Gain greater than-2d B within ±30°.In2GHz?12GHz,when ? is ±30°,the mode 2 beam Gain is not less than-5d B,meeting the technical requirements of the project.In chapter 4,an SC band four-arm sinuous antenna for interferometer direction finding is designed.The metal ring is loaded at a certain distance away from the antenna arm to expand the bandwidth of the low frequency.Two pairs of antenna radiating arms are fabricated on both sides of the dielectric substrate for convenient connection to the designed low profile dual balun.A highly symmetrical feed point structure is designed to ensure the circular polarization of the antenna.The final antenna radius is 18 mm and the profile height is40.254 mm.The antenna can achieve Active VSWR below 2 in the operating band of2.7GHz?7.5GHz.The Axial Ratio Value of left-handed and right-handed circular polarization is below 3d B.The antenna unit has a wide beam width to meet the direction finding requirements,and the gain meets the project requirements at each frequency and scanning angle after arraying.