Design Of Wideband And Miniature Antennas In Very High Frequency

VHF communication is becoming more and more popular in aviatic communication equipment,and requirements of VHF antenna are getting higher and higher,making the broadband and miniaturization design of VHF antenna become a hot spot.Therefore,this paper studies the broadband and miniaturization technology of VHF antenna based on the development and application of VHF antenna,and introduces the basic theoretical knowledge of the sleeve antenna which belongs to the broadband antenna,and gives a supplement with some practical examples in order to obtain more comprehensive understanding of the sleeve antenna,which will be helpful in design of ultra-shortwave sleeve antenna.Three sleeve antennas were designed in this paper,and operating frequency range is100~400MHz.The first one is the sleeve dipole antenna with the loading of metal rings,in the inner wall of the sleeve symmetrically loads two metal ring,it can effectively improve reactance in the high frequency band,and then expand the antenna bandwidth;The second one is a biconical sleeve dipole antenna,the use of biconical structure and increasing radius of the end of the radiator method is a good way to broaden the bandwidth of the antenna,and it has a simple structure,and is easy fabricated;The third one is a miniaturized sleeve dipole antenna,it used top loading,media loading to achieve the purpose of size reducing,which is on the basis of the metal rings sleeve dipole antenna.These three antennas have very good broadband characteristics and horizontal omnidirectional radiation characteristics.In the last chapter,the proposed antennas are arranged in vertical coaxial to form a composite antenna,which can make the antenna to work in different frequencies at the same time.By adjusting the distance between the antennas to meet its isolation requirements of greater than 20 d B,on this basis,the mutual coupling between the antennas is small in the vertical direction,therefore,the antennas still have great broadband and omnidirectional characteristics.