Product category:
Antennas and Feeders
News Release from: Sarantel | Subject: GeoHelix-H
Edited by the Electronicstalk Editorial
Team on 23 April 2002
Novel GPS antenna picks up more
satellites
The GeoHelix-H is a new-technology high-gain active antenna for portable GPS receivers which enables more satellites to be acquired than conventional patch devices.
The GeoHelix-H is a new-technology high-gain active antenna for portable GPS receivers which enables more satellites to be acquired than conventional patch devices Developed by Sarantel, GeoHelix-H measures only 30.4 x 13.3 x 6.4mm and weighs 12g
This article was originally published on Electronicstalk on 27 Jun 2001 at 8.00am (UK)
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The GeoHelix-H operates over the L1 GPS band and has an integral low noise amplifier (LNA) which provides a typical gain of 20dB.
Its omnidirectional pattern along with a 3dB beamwidth of 120 degrees enables more satellites to be 'seen' by the antenna than would be possible with a patch antenna.
Furthermore, it does not require a bulky ground plane, making it easy to incorporate in small portable GPS receivers, tracking devices or GPS-equipped notebooks and PDAs.
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GeoHelix-H has two additional benefits.
The balanced design allows it to reject common-mode noise, and it has a very low near field meaning that it is not detuned when in proximity to body tissue.
This also means that it is suitable for positioning next to another antenna, such as that used with new-generation mobile handsets or Bluetooth-equipped peripherals.
GeoHelix-H uses the same advanced design and manufacturing process as Sarantel's current passive and low-gain antennas, the specially-matched LNA simply increases the GPS signal level while keeping the noise level down.
The amplifier, which provides an output impedance of 50ohm, is mounted in an attached plated plastic case.
This is supplied with either an female MCX connector or it can be fitted with a patch cord which can be supplied with popular connectors such as MCX, MMCX and SMA and SSMT.
During the latter stages of the development of the GeoHelix-H, comparative tests were carried out in Taipei using Sarantel's antenna and a regular 26dB active GPS patch antenna: both were connected to identical Compaq Ipaq handheld computers running the relevant software packages.
Taipei is notoriously difficult to navigate reliably using GPS because of its highly built-up urban, electrically noisy radio environment.
The performance of the two antennas was comparable in some situations, but performance in heavily built-up areas and in difficult situations such as the re-acquisition of a GPS fix, when emerging from tunnels, the performance was considerably better with the GeoHelix unit.
Re-acquisition typically took only 12% of the time required by the patch equivalent.
In-car performance was particularly improved, as Tod Urquhart, Sarantel's sales and marketing director, remarked, "We were confident we'd get good results but there were certain aspects of the GeoHelix performance, such as the rapid re-acquisition, that surprised even us.
For portable applications, size and weight are particularly important, so being able to provide equivalent or better performance with such a small antenna is just what some of the new personal tracking applications demand".
The patented antenna design, developed by Sarantel in conjunction with Loughborough University UK, uses copper tracks, deposited on to a small ceramic cylinder which is individually and automatically laser-trimmed for optimum frequency response.
The robust antenna measures only 13.3mm in diameter by 30.4mm and will save space for in-vehicle and handheld GPS applications.
(This was Electronicstalk's Top Story on 22 April 2002).
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