GPS Reviews & Technology

SiRF Star III GPS Chipset Powering Location Aware Mobile GPS Devices

The SiRF Star III chipset family has proved a watershed innovation GPS chip architecture by offering impressive performance improvements to the GPS receiver manufacturing industry. They have been adopted by major GPS manufacturers including Garmin, TomTom and Magellan. The SiRF Star III chipset family was developed by SiRF Technology Holdings, Inc. (SIRF – Nasdaq Stock Exchange) of San Jose, California.

SiRF Star III chipset
There are three primary reasons why SiRF Star III chipsets are a revolutionary (evolutionary) development compared to previous products:

1. Faster fix times
As covered in more detail in our GPS technology overview, GPS satellites emit coded GPS signals designed to enable the receivers to recover necessary positioning information. By acquiring the signal of a minimum of four satellites, and determining the difference between signal transmission and reception times a GPS receiver can triangulate and calculate its latitude, longitude and elevation.

Receivers determine the arrival time of coded signals by comparing a locally generated reference signal against the received satellite signal – sliding the local reference in time until it is time-aligned with the received signal. The comparison process, achieved by a by a mathematical multiplication and integration process, is known as correlation.

Because of the signals cycle length and frequency there are a limited number of possible match/correlation points. Instead of performing all the correlation calculations in a sequential fashion, the SiRF Star III chipsets perform them in parallel. In fact the SiRF Star III family has over 200,000 correlators allowing it to perform all the calculations to establish a signal match simultaneously. So the signal fix time is determined by the infinitesimal time to perform a single signal matching calculation.

2. Higher signal locking and tracking sensitivity
If a GPS receiver is in a heavily signal obstructed environment, such as a built-up central city location or forest, it obtains only short bursts of satellite signals. As the whole satellite signal locking process must be restarted if a lock is not obtained in an available window, a receivers locking sensitivity is dependent on the speed it can match and lock on a satellite signal. Therefore SiRF Star III chipsets, with their speed advantage of massively parallel correlation engines, can achieve a satellite lock in reception windows other receivers would find too short giving it higher signal locking and tracking sensitivity.

3. Much lower power requirements
The SiRF III family has been designed to have minimal power requirements giving GPS receiver manufacturers an advantage to provide both longer battery charge life and smaller form factor mobile devices. In a double advantage, manufacturers now also have higher performance, smaller form factor lithium iron batteries (have you noticed the rapidly diminishing size of digital cameras lately?).

What opportunities does this technology jump open?
With improved signal acquisition and tracking reliability and lower battery power requirements and form factors the environment is set for manufacturers to push the pervasion of GPS location awareness into a multitude of mobile devices including cell phones, personal digital assistants (PDAs), music players, video players, cameras, watches (Dick Tracy eat your heart out) and notebook PCs.

Teamed with Location Based Services, this GPS technology leap is set to change all our lives.

Categories: GPS Technology

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