Research On Low-construct Horizontal Antennas Of Very Low Frequency

The wave-length of VLF is from10km to100km. It has some very important charactersfor the communication of subwater and underground, such as the long depth of penetratinginto the ground or sea, the stable propagation and the small weakening. As the result, theVLF EM wave is mainly used in communication with submarines, navigation, time serviceand magnetosphere. The VLF communication is the master method for submarine in navy ofall over the world, which can help the submarines to hide in the sea when they are inwarfare.Nowadays, the Tx antennas for VLF wireless system are most vertical monopoles.Because the wave-length is very long, the size of VLF transmit antenna is very large. TheVLF Tx antennas are usually supported by huge towers with several hundred meters heightor by mountains. The defects of the VLF Tx antennas are also obvious: the limited fightdamage ability, small bandwidth, communication ability low, and bad anti-jam ability.According to this condition, this paper proposes a low-construct horizontal antenna for VLFtransmit system.Based on the hybrid potential integral equation (HPEI) and the discrete complex imagemethod (DCIM), the full-wave model is established for the low-structure horizontal antennawith arbitrary shape. The full-wave model is solved by MoM, with which the numericalresults can be obtained for single antenna or array with or without loading. The analysismodel is check out by comparing the results with the published experiment results.In order to study the effect of the capacitance loading, the mode equation of thepropagation constant for the low construct horizontal antennas is formulated. It is proven intheory that fast wave mode will be excited along the antenna with suitable capacitor loading.By using the MoM model, the effect of antenna parameters on the electric performance isanalyzed and the optimization of the radiation efficiency is discussed. A proposal of the lowconstruct horizontal antenna array is presented for the practical VLF wireless system basedon the research of single antenna. The numerical simulation shows that the efficiency of thisarray is exceeded10%. The electric performance of the presented proposal is analyzed indetail in this paper and the high power feed technology is also discussed.