The GPS signal uses a modulation scheme called CDMA for spectrum diffused transmission. The spectrum diffused signal is buried by natural noise. The GPS receiver contains a duplicate of the diffusion code in correlation to the transmitted signal, and uses overlap processing (inverse diffusion) to extract the buried signal from the noise.
The signal is so weak that a normal GPS receiver cannot determine a position in areas obstructed by buildings, etc. For these situations, a high sensitivity receiver is required.
A high sensitivity receiver is a GPS receiver that can extract and calculate a position from a weak signal that is 1/1000 of a typical outdoor signal. With this kind of sensitivity, a position can be calculated in many different indoor situations. This type of receiver is designed to improve upon the weaknesses of GPS receivers that do not perform well inside buildings or obstructed areas, and can be used indoors or underneath elevated structures.
To extract a weak signal that is only 1/1000 the strength of a normal signal, an especially large amount of correlation processing is required for a sustained period. Correlation processing allows a signal to be targeted from the confusing mix of false signals generated by noise and other satellites aside from the target satellite.
Circuit with a number of correlators, necessary for high precision positioning, is effectively integrated into the the high-sensitivity GPS/GNSS receiver chip "eRideOPUS 7" in high density by utilising our proprietary technology.
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