Helical antennaby

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.

Radiation pattern

Cylindrical 3 strip antenna

Hfss module

Resoanace frequency 2.77GHz return loss -17db

Radition pattern

Cylindrical 2 strip antenna

Resoanace frequecy vs s11resonace frequency=3.41GHz and return loss=-

17db

Radiation pattern

Cylindrical single strip

Frequency vs return loss

UPPER L ,C LOADING L=3MICRO H ANDC=3NF LMIDDLE L ,C LOADING L=2MICROH AND C=2.2NF,LOWER L ,C

L=3MICRO H ANDC=2.5NFGROUND PLANESI=3000X3000 MM

Bifolded monopole antenna for naval commnication H=24cm,W=4cm,w=1.6cm,h=12cm

H

h

L

L

C

C

CL

Hfss design

Vswr<3 from 4mhz to 30mhz

Impedance of antenna

References…….. 1-Antenna theory analysis and design third edition “constantine

A.balanis page 27 to 102.and page 497 to 521 and page 557 to 575. 2-cylindrical antennas and arrays and enlarged 2nd edition of array of

cylindrical dipole Ronald ,W.P.king George J fikioris,rechard B.Mach. 3-IEEE transation on antennas and propagation, vol41 no.2

febuary1993 Cylindrical rectangular microstrip patch antenna for circular

polarization”keh lu wong shyh-yeong ke” 4- A curved spiral antenna above a conducting cylinder (Hisamatsu

Nakano, Fellow IEEE,and Kazuo Nakayama, Member IEEE) IEEE Transactions on antenna and propagation , vol,47,no.1,january1999.

5-IEEE Transation antennas and propagation vol.56.no.3 march 2008. Metamaterial-inspired efficient electrically small antenna.”Aycan

Erntok.member ,IEEE,and Richard W.Ziolkowski,fellow ,IEEE. 6-IEEE antenna and wireless propagation letters,vol 4,2005. 7-Design of a broad band HF antenna for multimode naval

communication Lorenzo Mattioni and Gaetano Morrocco, Member, IEEE.