Helix Antenna
Helix antennas are used in space applications, satellitesystems, radar systems, TV signal transmission, etc.
Usually, a helix is manufactured as a wire, coiled
around dielectric cylinder.

Our aim is to compare simulation times, numbers of
unknowns and radiation patterns for simulatedantennas. We will assume that given antenna is used inI-band (NATO bands classification).

Main characteristics of helix antennas are•

Circular polarization,•

Broad-band,•

Two operation modes depending of usedfrequency,•For unifilar helices, using a reflector isnecessary.

Several models of helix antennas are created andsimulated in WIPL-D Pro and presented here. Onemodel is made of wires; another model is made ofplates while the third model is made of plates coiled
around the dielectric. The wire model is shown inFig. 1, plate model is shown in Fig. 2 and plate modelwith dielectric rod is shown in Fig. 3. Main dimensionsof these antenna models are the same. Some differences
exist, because of using wires and plates which are ofdifferent geometrical shapes. Parameters of thedielectric are:•ε r = 2 + j⋅ 0 ,•µ r = 1+ j⋅ 0 .

Figure 2. Plate helix model

Figure 3. Plate helix model with dielectric

WIPL-D Simulation
In WIPL-D Pro, helix antennas can be designed using
the built-in Helix object. Antennas shown in Figs 1-3
can be also modeled “manually” (using individual wires
as building blocks) but that would make modelingdifficult.

Figure 1. Wire helix model

Analyzed helix antennas consist of radiating elements
and a reflector.
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Here, metallic parts are considered to be perfectlyconducting. Central operating frequency is 9 GHz. Allof the antennas are used in axial mode.
Radiation pattern of the wire helix model in 3D isshown in Fig. 4. Overlaid 2D radiation patterns for
phi-cuts are shown in Fig. 5. Please note that the theta
angle is measured with respect to the xOy plane.
Near field of the wire model is given in Fig. 6. Numberof unknowns and simulation time of analysis are givenin Tab. 1. Computer used for these calculations isPentium® Core2 Quad CPU @ 2.83 GHz.
Figure 6. Near field of helix antenna made of wiresTable 1. Analysis characteristics

ModelNo. ofunknowns

MemoryWires

401

1.2

<1Plates

751

4.5<1Plates/dielectric

2245

40.3

3

Figure 4. Radiation pattern of wire helix antenna[MB]Time @
9 GHz[sec]

Conclusion
Using WIPL-D Pro Helix object with the possiblities
for parameterization, we can easily create andmanipulate helicoidal structures.
As we can see in Tab. 1, proper approximation of plate
helixes using wires can decrease number of unknowns
and simulation time. Gains from replacing plates bywires wherever possible can be much higher for more
complex structures.

Figure 5. Overlaid 2D radiation patterns for a phi-cut

We can see (Fig. 5) that helix antenna model with
dielectric has significantly different radiation pattern.
Reason for this is dielectric influence on antennacharacteristics. Dielectric is used because of antenna
physical solidity, but it changes the operating band ofantenna and thus must be considered in the design
process. The influence of dielectric is successfully
simulated in WIPL-D Pro.

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