International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Design of open ended Quadfilar helical antenna for
2.4 GHz
Vaibhav M Jotania#1,Ved Vyas Dwivedi*2, Jitendra P Chaudhari#3
#
Communication System Engineering, Charusat University
At & Po:Changa-388421, Dist-Anand,India
Abstract—There are two types of helical antenna (Monofilar
Helical Antenna and Multifilar Helical Antenna). In this paper,
the design of open ended quadfilar helical antenna(QHA) is
proposed. Antenna model is designed at the centre frequency of
2.4 Ghz. Details of antenna design parameters and simulation
results are presented along with Radiation Pattern, Axial Ratio
and gain.
Keywords— Quadfilar helical antenna(QHA), Axial Ratio.
I. INTRODUCTION
Helical antenn can be design as a monofilar helical antenna or
multifilar helical antenna.It is having two radiation modes.In
normal mode helix, the direction of radation is normal to the
axis of helix and in axial mode helix, the direction of
radiation is in the axis of helix.In multifilar helical antenna
more number of wires are wound. In quadfilar helical antenna
four wires are there and they are fed in phase quardature.
II. GEOMETRY OF HELICAL ANTENNA
The geometry of a conventional helix is shown in Fig.
1(a).The parameters that describe a helix are summarized
below.
D = diameter of helix
S = spacing between turns
N = number of turns
C = circumference of helix = 𝝅D
A = total axial length = NS
∝ = pitch angle
the relationships between S ,C,∝ and the length of wire per
turn, L , are obtained as below and shown in Fig. 1(b):
S =L sin ∝ = C tan ∝
L = (S 2 + C 2 )1 / 2 = (S 2 + π 2 D 2 )1/2
III. OVERVIEW OF QUADFILAR HELICAL ANTENNA
The quadrifilar helical antenna (QHA), also known as the
Kilgus coil, is mostly used for telemetry, tracking and
command (TT&C) satellite systems due to its simplicity,
small size, wide circularly polarized beam and insensitivity to
nearby metal objects. The QHA consists of four helical wires
equally spaced circumferentially and fed from the top or the
bottom. The open ended QHA generally uses the length of
each wire of λ/4 or 3 λ /4 while the short–circuited QHA uses
λ /2 or λ length of each wire. The open-circuit quadrifilar
helix antenna (O-C QHA), sometimes referred to as a volute
antenna, consists of four helical windings oriented 90° with
ISSN: 2231-5381
Fig 1. (a) Geometry of helix (b) Unrolled turn of Helix
small size, wide circularly polarized beam and insensitivity to
nearby metal objects. The QHA consists of four helical wires
equally spaced circumferentially and fed from the top or the
bottom. The open ended QHA generally uses the length of
each wire of λ/4 or 3 λ /4 while the short–circuited QHA uses
λ /2 or λ length of each wire. The open-circuit quadrifilar
helix antenna (O-C QHA), sometimes referred to as a volute
antenna, consists of four helical windings oriented 90° with
respect to one another, with each winding unterminated (opencircuited) at the ends away from the feed point. Typical
applications of the antenna include satellite, ground station,
GPS, etc. The Geometry of quadfilar helical antenna is shown
in fig. 2. The paprameters that describe quadfilar helical
antennas are Hh : Height of helix ,D : Diameter of helix, Hf :
Height of feed and N: number of turns.
The elements of the O-C QHA are excited in quadrature with
the relative phasing sequence 0°, 90°, 180° and 270°. Top
view is shown in fig. 2 in which Rg is radius of ground plane
and Rh is Radius of feed. The elements of the O-C QHA are
excited in quadrature with the relative phasing. Top view is
shown in fig. 3 in which Rg is radius of ground plane and Rh
is Radius of feed.
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
Fig 2. Geometry of QHA
Fig 4.Design of QHA
Fig 3.Top view of QHA
IV. GEOMETRY OF HELICAL ANTENNA DESIGN AND
SIMULATION RESULTS OF OPEN ENDED QHA
We have designed QHA with parameters which are shown in
Table 1. Fig. 4 shows that QHA is designed along z-axis at the
centre frequency of 2.4Ghz .
Fig 5.Return loss
N
1.08
Rh
Rg
Hh
Hf
D
8.66
17.33
71.75
1.33
666.7
mm
mm
mm
mm
µm
The results are generated using CST microwave studio.In
design, we used four waveguide ports for excitations. Fig. 5
shows the return loss of antenna at the centre frequency of
2.4 Ghz for the respective ports. Fig. 6 shows the Voltage
Standing wave ratio(VSWR).From the graph of VSWR it is
clear that value of VSWR is between 1 to 1.1 for all four
ports. Directivity of QHA is 2.2dBi at the 2.4Ghz as shown in
fig. 7. Fig 8, fig. 9,fig. 10 and fig. 11 shows the axial ratio at
the centre frequency 2.4Ghz at port 1,port 2, port 3 and port 4
respectively. Fig. 12 shows the 3D radiation pattern of QHA.
Fig 6.VSWR at the centre frequency
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
depends on diameter of helix, axial length of helix and
number of turns of helix.
Fig 7.Directivity of QHA
Fig 10.Axial Ratio at port 3
Fig 8.Axial Ratio at port 1
Fig 11.Axial Ratio at port 4
Fig 9.Axial Ratio at port 2
V. CONCLUSION
The frequency may be decreased by increasing the height or
increasing the radius of the QHA, which effectively increases
the length of the helical elements. It may be design as a RHCP
(Right hand circularly polarized ) or LHCP (Left hand
circularly polarized ). The Directivity, gain axial ratio are
ISSN: 2231-5381
Fig 12. Radiation pattern of QHA
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International Journal of Engineering Trends and Technology (IJETT) - Volume4Issue4- April 2013
ACKNOWLEDGMENT
The author is thankful to Dr. Ved Vyas Dwivedi and Prof.
J.P.Chaudhari for giving full support and motivation during
research work.
REFERENCES
[1]
[2]
[3]
[4]
C.C. Kilgus, ―Multielement, fractional turn helices‖, IEEE
Transactions on Antenna and Propagation, July 1968, pp. 499 – 500.
C.C. Kilgus, ―Resonant quadrifilar helix‖, IEEE Transactions on
Antenna and Propagation, May 1969, pp 349 – 351.
C.C. Kilgus, ―Resonant quadrifilar helix design, Technical Feature‖,
Microwave Journal, December 1970, pp. 49 – 54.
C.C. Kilgus, ―Shaped-conical radiation pattern performance of the
backfire quadrifilar helix‖, IEEE Transactions on Antenna and
Propagation, May 1975, pp. 392 – 397.
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