subject: A Guide To Gps Antennas For Global Positioning System [print this page] The GPS antenna industry is expanding, thanks to the increasing production of mobile phones and portable devices supporting GPS function. Makers continue to broaden the range to improve exports. Most models in their catalogues are used in vehicle tracking and portable navigation devices, and in RFID scanners for logistics and cargo handling.
GPS antennas are what aids to boost the reception signal to a GPS receiver, whether it's a standalone receiver or an embedded receiver. The GPS antenna is used to collect the GPS signals and coax cable is used to transfer signal information between the GPS antenna and receiver. A GPS antenna can receive signals from the GPS satellites when it is almost anywhere on earth. The electrical phase centre of GPS antenna at both ends of baseline has the same changes with GPS satellite receives.
Typically a GPS antenna is utilized in a situation where the GPS receiver itself is somehow faraway from a line of sight to the sky, (as in a car), to assist the GPS receiver see the sky without having to be moved.
Although antennas are simple to design and construct, they do not perform until tuned to resonance or to the frequency of use. Tuning is the process of adjusting the complex (real & reactive) impedance of the antenna to get the best impedance match (lowest SWR) to the 50 ohm transmission line and transmitter. Most civil GPS receivers access the C/A-code (coarse/acquisition code) transmitted on the L1 frequency (1575.42 MHz).
GPS antennas do not need a ground plane so they can be mounted on insulation if desired. The top of rollover structures or the top of the panel or the rear deck all work well. However, never mount a GPS antenna at an angle to the horizon, since, the antenna cannot "see" below that angle.
For applications where longer cable lengths are required, a high gain antenna is needed. The high gain is necessary to compensate for the additional losses that will be experienced in longer cables up to 600 ft (200 meters).
by: Chris Cowper
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