Helical antenna by subhash yadav under guidance of prof..Bratin ghosh
antenna diamentions Monopole hight=595mm.copper Monopole radius=1mm. Helix pitch length =20mm. Helix radius=50mm. Nomber of turns=25. Rect hight=15mm. Rect metal thickness=10mm copper Ground plane =5000X5000 mm. Total helix hight=25(15+20)=875mm Coaxial feed is given inside the ground outer radius of condutor is shown in figure and inner radius is radius of monopole antenna.
Basic priciple Helix antenna is exited by electric field generated by monopole in near field. Flux is captured by helix antenna and change of flux with time produced induce current in helix this induce current produces inductance in the system. Strong electric field genrated by monopole antenna in near field create capacitance in the syastem. The conductor loss is due to monopole antenna radius and thickness of metal strip. So RLC system form in whole system . Monopole antenna and helix are properly adjusted for tuning if helix pitch length is small and rectangle length is large it produce large inductance because higher metal density.
Hight of monopole antenna dermine resoanace behavior of antenna higher monopole length create strong resoanace and small monopole create low resonance . This antenna can be scale defferent frequency range for proper adjustment of monopole hight and helix paramer. This antenna is design for naval communication in the frequncy of 18.6 MHz. This antenna shifted lower frequency by increasing pitch of helix because metal density between two turns are reduce.
Ansoft hfss simulated results Resoance frequency=18.6MHz and corresponding S 11=-9.5db.as shown in frequency vs S11 graph.
Bifolded monopole antenna for naval commnication H=24cm,W=4cm,w=1.6cm,h=12cm C L H L C h L CUPPER L,C LOADING L=3MICRO H ANDC=3NF LMIDDLE L,CLOADING L=2MICROH AND C=2.2NF,LOWER L,C L=3MICRO H ANDC=2.5NF GROUND PLANESI=3000X3000 MM
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