Iridium Antennas

MARUWA offer a unique class of dielectric-loaded multi-filar antennas which provide unrivalled performance in applications which:

  • • The device is handheld, body-worn, or otherwise surrounded by materials of high relative dielectric constant which would de-tune other antennas.
  • • The antenna is installed in close proximity to other antennas sharing the same device housing and ground plane and it is necessary to avoid cross-interference. For example if a MARUWA GPS receiving antenna is co-sited with Bluetooth, Wifi, LTE, WiMax, or cellular radio antennas, there should be no impairment of performance.
  • • The antenna must fit into a very small installation volume with close proximity to other components and little or no space available for a ground plane.
  • • The orientation of the device may not be ideal so that the antenna’s omni-directional broad beam-width is required.


The Most Important Detail: A Pattern with Broad Beam-Width

  • • MARUWA’s multi-filar antennas offer a broader angle of reception than patch antennas.
  • • This enables the antenna to track more satellite signals even when the device is tilted from the upright angle of use.
  • • The device provides faster and more robust position fixes and an overall better user experience.










14(D) x 33(L)


Iridium Applications.
Waterproof, dust proof.



Maruwa Sarantel Multi-filar Antennas – How They Work

RHCP Definition(from source)
RHCP Definition (from source)

MARUWA helical antennas are designed for circular polarisation.
and Iridium satellite systems use right-hand (RH) circular polarisation.
Polarisation conventions are always defined from the perspective of a source. Passive antennas obey the law of reciprocity so similar definitions can made for receiving antennas.
The sense of polarisation is called right-hand if the direction of rotation of the electric-field(in a transverse plane) is clockwise when viewed by an observer, looking from the transmitter to the receiver, along the direction of propagation.

A circular-polarised antenna can be visualised as a spinning dipole. In this animation we are viewing from above, so according to the definition, the antenna will transmit a RH-circularly polarised signal in the direction of the green arrow.

Spinning Dipole (from above) RHCP pattern radiated above.
Spinning Dipole (from above) RHCP pattern radiated above.

However if the same spinning dipole is viewed from below we observe that the dipole is spinning in the opposite direction. Therefore the planar signal in the direction of the pink arrow (below). This is not desirable. We want to the antenna to look only at the sky upwards and not at the ground downwards.

Spinning Dipole (from below) same antenna radiates LHCP pattern below.
Spinning Dipole (from below) same antenna radiates LHCP pattern below.

The microstrip- patch antenna solves this problem with a metal ground-plane which acts as a mirror. If a LH-circular polarised signal is reflected in a mirror it changes to RH-circular (clockwise rotation is reflected as anti-clockwise rotation). Thus the LH-circularly polarised reverse-going wave is reflected as a RH-circularly polarised component to combine with the RH-circularly polarised signal from the forwards direction of the spinning dipole. If the ground-plane is large enough no power is wasted.
designers have the difficulty that the ground-plane needs to be large to be effective: at least /4 in diameter (about 5 cm for GPS L1). Many products cannot be styled attractively with this approach.

The patch antenna reflects from the ground-plane to concentrate radiation into wanted RHCP polarisation. But the ground-plane must be large.
The patch antenna reflects from the ground-plane to concentrate radiation into wanted RHCP polarisation. But the ground-plane must be.

The MARUWA multi-filar antenna solves the designer’s styling problem by resonating with a repeating “cork-screw” motion. The reverse-going LH-circular polarised wave propagation is suppressed because the spinning-dipole is “travelling” in the forwards going direction. This form of antenna can concentrate RH-circular polarisation in the forward-going direction without a ground-plane.

Reverse-going LHCP is suppressed because the “spinning” dipole is “travelling” in the forward going direction.
Reverse-going LHCP is suppressed because the “spinning” dipole is “travelling” in the forward going direction.

Of course circularly-polarised antennas do work by physically spinning a dipole. The MARUWA multi-filar antennas connect at least 2 dipoles together but with a phase-shift between them so that this combination of two or more antennas together synthesise the effect of a spinning dipole. In this hexafilar example three “twisted-loop” dipoles are combined together in a structure that radiates with circular polarisation.
Because circular polarisation always requires a combination of dipole antennas connected together in this fashion it is always very efficient in terms of use of volume: two or more dipole antennas are combined together in the same space.

Resonance of a MARUWA hexafilar antenna.
Resonance of a MARUWA hexafilar antenna.

MARUWA Resonant Structure

The MARUWA antenna structure operates with two co-operating resonance that are supported by a metal pattern that is printed onto a low-loss MARUWA dielectric material. The structure is back-fire fed from a balanced (two-terminal) connection. In the decafilar example that is shown opposite each terminal is connected to fixe helices which are each resonating in a twisted loop that is formed with the opposite helix that is connected to the other terminal. The phasing of the five twisted loops is managed by a circular wave-length resonance of the “balun-rim”.

The lower metallised part of the structure functions as a sleeve balun (un-balanced to balanced transition). This structure isolates the antenna’s radiating section from the device ground-plane so that the antenna’s resonance is independent from the housing. The device configuration can easily be designed so that human-body loading does not detune or significantly reduce the efficiency of the antenna. Also as a balanced structure incorporating a balun, the antenna does not pass common-mode ground noise to the receiver input.

balanced load

MARUWA RHCP elevation pattern.

The effect of incorporating an isolating structure (balun) together with the high-quality design of the antenna provides excellent performance. The use of distinctive dielectric materials technology concentrates resonance fields into the dielectric core (across which fields are balanced at all times). Therefore the antenna can provide excellent pattern performance when tightly integrated into the device even when close to cluttering objects (LCD, switches, connectors etc).

In addition to increasing the efficiency of the antenna, the addition of a greater number of helices to the MARUWA antenna improves the quality of circular polarisation. This is because the greater number of helices promotes a smoother rotating effect.

MARUWA decafilar resonance.
MARUWA decafilar resonance.

The MARUWA antenna structure can be used in applications which require a well defined phase-centre. The excellent circular-polarisation performance means that phase can be un-wrapped to a point. Unlike planar antennas there is no surface-wave parasitic mode.

MARUWA technology supports accurate position measurements.
MARUWA technology supports accurate position measurements.


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