Deployable Quadrifilar Helical Antennas for Various Frequency Bands

Deployable Quadrifilar Helical Antennas for Various Frequency Bands

Deployable Quadrifilar Helical Antennas Available for Various Frequency Bands
Greg O’Neill

Helical Communication Technologies
634 Barnes Blvd, Rockledge, FL 32955 (321) 208-8978

[email protected]

ABSTRACT

Quadrifilar Helical Antennas (QHAs) are very appropriate for Low Earth Orbiting small satellites because they offer
better useable footprints on Earth than simple monopole antennas. A comparison between a monopole and a
Quadrifilar Helical Antenna will be presented. Results of a recent project will be presented. Measured antenna
performance provided good correlation with the simulations. Simulations have been performed for satellite
frequency ranges from 350 MHz to about 3 GHz. Simulations are based on deployable antennas suitable for
occupying about one third to one half of a 1 U size structure. There is good confidence that the simulations to be
presented can be developed into useable QHAs.

The Quadrifilar Helical Antenna can provide a greater coverage footprint on Earth than simple linearly polarized
monopole antennas or circularly polarized patch antennas. The antennas for this application were comprised of two
bifilar loops. Antennas using this approach should be used in a loop configuration to be able to apply the direct
current. So far, Quadrifilar Helical Antennas and Spiral Antennas have been found to be suitable for this technique.

The Quadrifilar Helical Antenna dimensions can be tailored for small size with less coverage area or larger size for
greater coverage area. Iso-Flux QHA’s can be provided for greater range at longer slant angles. Recent advances in
Quadrifilar Helical Antenna development for small satellites now allow the antenna to be stowed within 1U to 12U
modules.

Utilizing Deployable Quadrifilar Helical Antennas on Small Satellites

As small satellites move toward higher frequency bands, it will be increasingly important to utilize better antennas.
A more definite and repeatable antenna pattern footprint on earth is important. The QHA can overcome fading due
to cross polarization of linear antennas. When a QHA is used on the satellite as well as at the ground station, easier
communications may result without the need for high gain ground station antennas that require a tracking means to
point to the small satellite.

QHA simulations indicate the potential for improved small satellite communications. HCT has an available
capability to develop QHAs for frequencies from about 350 MHz to about 3 GHz.

The QHA circularly polarized antenna gain is normally designed to be just over 3 dBicp for near hemispheric
radiation patterns. Pattern goals can be the ISO-Flux pattern where more gain is adjusted for maximum slant range
and less gain at the nadir. For other purposes, such as lunar or other deep space objectives, HCT has an ability to
develop high gain QHAs to 12 dBi. The high gain QHA’s have much narrower beam widths accordingly to their
higher gain.

One of the reasons QHAs are not prevalent on small satellites has to do with their complicated structure and need to
remain dimensionally true when deployed. Small antenna modules can be developed with a means to deploy the
QHA structure after launch. Recent advances in Quadrifilar Helical Antenna development for small satellites now
allow the antenna to be stowed in one-third to one-half of a 1U module portion of a small satellite.

Greg O’Neill 1 Space Tech Expo 2016
Helical Communication Technologies

Deployable Quadrifilar Helical Antennas for Various Frequency Bands

Deployable QHAs need Attitude Control The monopole antennas are mounted on either side of
the small satellite.
Typically, quarter wave monopole antennas are
mounted where they can be fitted on small satellites,
perhaps without positioning for the best antenna
patterns. The QHA must be positioned with the axis
pointing to Earth using the attitude control of the
satellite.

Practical Frequency Range

The frequency bands from 350 MHz to 3 GHz are
appropriate for deployable storage in portions of 1U
size structures. The practical lower frequency is limited
by the diameter of the structure. We may be able to
design antennas higher than 3 GHz, but we have not
done so to date.
If larger module sizes can be accommodated, then
lower frequency QHA’s could be developed.

Consider a 436.5 MHz Horizontal Monopole on 1U
Small Satellite

Many small satellites employ a simple monopole. The
radiation pattern is reasonably good at this frequency
for communicating short message information.

For a satellite orbiting in the +Y direction, a wide beam
width is provided in the –X to + X direction. However,

the dwell time will be rather short.

For a satellite orbiting in the +X direction, good The lower half of the pattern may be directed to earth.
coverage is provided along the path of the orbit. The beam width is about 80 degrees
However the coverage on either side is limited.

Greg O’Neill 2 Space Tech Expo 2016
Helical Communication Technologies

Deployable Quadrifilar Helical Antennas for Various Frequency Bands

View of a Stowed QHA on a 90 x 90 mm Grid

Simulation of an ISO-FLUX 2200 to 2400 MHz
Quadrifilar Helical Antenna

Dimensions for this 2.3 to 2.4 GHz QHA are: Stowed Axial Height is less than 35 mm.

Axial Height ~148 mm The QHA may be stowed and recessed into a portion of
a 1U cube sat. The antenna is placed within a suitable
Diameter ~ 30 mm plastic module to be a portion of a 1U cube satellite.

View of the Iso-Flux QHA on a 90 x 90 mm on a 2U
Small Satellite

Pitch Angle ~ 45 degrees

Filar Diameter ~ 1.5 mm

The QHA is attached to a 90 x 90 mm grid, as part of a

side of a small satellite.

The ISO-Flux radiation pattern

Greg O’Neill 3 Space Tech Expo 2016
Helical Communication Technologies

Deployable Quadrifilar Helical Antennas for Various Frequency Bands

Simulation of a High Gain 400 MHz tapered
Quadrifilar Helical Antenna

The antenna is tapered to facilitate stowing.

Close up view of the stowed 400 MHz QHA.

The overall axial height is about 1.5 meters.
The bottom diameter of the QHA is 80 mm.

The overall height of this stowed antenna is
about 72 mm.

These are simulated results. We have not A 3D view of the 400 MHz QHA radiation
built this antenna yet. pattern.

We believe we can handle the long axial
height of this structure.

The antenna is deployed by applying a direct
current to the Nitinol wires for one minute.
This DC power would be applied safely long
after leaving the rocket dispenser.

Greg O’Neill 4 Space Tech Expo 2016
Helical Communication Technologies

Deployable Quadrifilar Helical Antennas for Various Frequency Bands

Simulation of a 436.5 MHz Quadrifilar Helical A side view of the stowed 436.5 MHz QHA. The pitch
Antenna on a 2U Small Satellite angle is reduced to 5 degrees. The height is reduced
from 208 mm to 35 mm.
The 3D antenna radiation pattern shows the wide beam
width for this rather small antenna on the 2U small
satellite.

Dimensions for this 436.5 MHz QHA are:

Axial Height ~208 mm

Diameter ~ 80 mm This 436.5 MHz is shown as an example of a small
realizable antenna for this band. It can provide good
Pitch Angle ~ 65 degrees gain for a large omnidirectional coverage area.

Filar Diameter ~ 1.5 mm

The QHA is attached to a 90 x 90 mm grid, as part of a

side of a small satellite.

Greg O’Neill The 3 dB Beam Width is almost 140 degrees at all
Helical Communication Technologies azimuth angles.
The Max Gain is plotted as 3.95 dBicrhcp,

5 Space Tech Expo 2016

Deployable Quadrifilar Helical Antennas for Various Frequency Bands

Picture of an L-Band Small Satellite

Measured Results for the Deployable L-Band QHA

A view of the Stowed Deployable QHA

Trace colors indicate low, mid, and high frequency
performance.

Picture of a Deployable L-Band QHA Module

Summary
Helical Communication Technologies can
accommodate a wide variety of Quadrifilar Helical
Antenna requirements.

Greg O’Neill 6 Space Tech Expo 2016
Helical Communication Technologies