Satellite-based positioning system improvement

Abstract

A method, device and system for determining a receiver location using weak signal satellite transmissions. The invention involves a sequence of exchanges between an aiding source and a receiver that serve to provide aiding information to the receiver so that the receiver's location may be determined in the presence of weak satellite transmissions. With the aiding information, the novel receiver detects, acquires and tracks weak satellite signals and computes position solutions from calculated pseudo ranges despite the inability to extract time synchronization date f, 'n the weak satellite signals. The invention includes as features, methods and apparatus for the calibration of a local oscillator, the cancellation of cross correlations, a Doppler location scheme, an ensemble averaging scheme, the calculation of almanac aiding from a table of orbit coefficients, absolute time determination, and a modified search engine.

Description

[0001]This application claims the priority filing date of U.S. Provisional Application Ser. No. 60 / 416,367 filed on Oct. 4, 2002.FIELD OF THE INVENTION[0002]This invention relates to the design of receivers employed in satellite-based positioning systems (SPS) such as the US Navstar Global Positioning System (GPS), the Russian Global Navigation Satellite System (GLONASS) and the European Galileo system. More specifically, the invention relates to methods, devices and systems for determining a receiver location using weak signal satellite transmissions.BACKGROUND OF THE INVENTION[0003]Satellite based positioning systems operate by utilizing constellations of satellites which transmit to earth continuous direct sequence spread spectrum signals. Receivers within receiving range of these satellites intercept these signals which carry data (navigation messages) modulated onto a spread spectrum carrier. This data provides the precise time of transmission at certain instants in the signal ...

AI Technical Summary

Benefits of technology

The patent text describes a method for acquiring and tracking satellite signals using a search engine and a modified acquisition system. The invention aims to improve the efficiency and energy requirement for acquiring and tracking satellite signals. The method includes a search range of at least 60 chips after acquisition of the first satellite. The invention uses an algorithm to measure the amplitude, frequency, and phase of the satellite signal and a timer to turn the receiver on and off. The invention also addresses the issue of initial position uncertainty by using an algorithm to measure the code phase differences of the satellite signal. The invention utilizes a higher correlator output sampling rate to estimate the amplitude of the residual carrier signals in the code phase measurements. The method also includes a window operation to improve the signal-to-noise ratio and a squaring operation to remove the data. Overall, the invention provides a more efficient and energy-effective way to acquire and track satellite signals.

Problems solved by technology

Moreover, subsequent fixes require equally as much energy as the satellites must be acquired from scratch again.

Firstly, the power hungry search engine can be turned off.

Secondly, the entire receiver can be duty cycled over quite long periods to achieve considerable savings.

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