| VHF comnunication has an irreplaceable position in trunking communication,to-air communications,data link communications,and VHF communication is an important complement in cellular mobile communication systems and satellite communication system,With the continuous development of modem VHF communications applications,we put forward new demands VHF antenna under the conditions of the particular application,VHF antenna with low Profile,ultra-wideband,high power is a very important antenna type with a practical application background.For a long time,quadrifilar helix antenna is a kind of classic VHF wideband antenna,it has a wide range of applications in high power-efficient transceiver VHF antenna.Low-profile VHF wideband high-power antenna is a new antenna needed in special applications environment,not only need the antenna keep high power and high efficiency,but also good characteristics of a low-profile shaped covert.This paper introduces the research background and progress of the helical structure of the antenna,propose the significance of the helical antenna。This paper analyzes the antenna radiation theory,analysis methods of radiation pattern of spiral structure antenna,feeding mode,and introduces the principle of small antennas。At last we will design a improved quadrifilar helix antenna with lumped element matching network.The antenna size is about 175mm × 175mm × 200mm.It has some theoretical reference value.The main contents of this paper are:1、In the overall structure of the antenna size,By using of the characteristics of the spiral structure to increase the electrical length of the antenna,reduce the height of the antenna.2、Introducing lump element feeding network,using HFSS and AnsoftDesigner co-simulation function to optimize the network performance and make it better for the helical structure of the antenna input impedance offset and balance to achieve impedance transformation effects and show wide bandwidth to achieve matching in the frequency band.3、By changing physical length of each spiral arm of the quadrifilar helical antenna to achieve 200MHz～600MHz frequency band.According to the above methods,the paper realize the low profile quadrifilar helical antenna VHF broadband,height of about 200mm,VSWR less than 3 in the entire band,gain greater than 2,omnidirectional radiation level in a good performance.By adjusting the electrical length of each helical arm to cover different frequency bands.Therefore,this paper has a good significance to design a low-profile broadband antenna design. |
