Method and device for acquiring weak global navigation satellite system (GNSS) signals
First Claim
1. In a navigational system utilizing a plurality of satellites that transmit radio-frequency signals containing time and orbit information of said satellites, a method of acquiring said satellite signals at a receiver, the method comprising:
- receiving a satellite signal at the receiver;
performing short-length correlations between the received satellite signal and locally generated reference codes, wherein each short-length correlation spans approximately 1 ms;
performing block accumulating coherent integration of said short-length correlations over a preset extended length, wherein performing the block accumulating coherent integration includes;
reducing frequency error for a block of short-length correlations prior tointegrating said block with preceding blocks over said preset extended length;
adding said frequency error reduced block of short-length correlations to partialsums of previous blocks of short-length correlations, thereby updating said partial sums, wherein each partial sum is added for a different possible data bit edge and a corrected bit sign of said block; and
making a decision based upon said updated partial sums to ascertain the presence or absence of said satellite signal up to this point.
3 Assignments
0 Petitions
Accused Products
Abstract
A Global Navigation Satellite System (GNSS) receiver and associated method capable of acquiring weak GNSS signals from a plurality of GNSS satellites produces a GNSS signal'"'"'s code time, carrier frequency, and data bit transition parameters for subsequent signal tracking and position fixing. The GNSS receiver includes a baseband signal processor with special functionalities for acquiring weak signals. In a preferred embodiment, the time and frequency uncertainty space is reduced using available information and then special techniques are used to rapidly search the remaining uncertainty space. Successive reversal of short-length correlations within a data bit interval (a block) enables data bit transition detection and data bit sign correction prior to coherent integration. Fast Fourier Transform (FFT) is applied as a bank of bandpass filters to coherently accumulate blocks of short-length correlations over extended coherent integration intervals to boost the signal power while averaging noise out despite unknown data bit transitions.
58 Citations
20 Claims
-
1. In a navigational system utilizing a plurality of satellites that transmit radio-frequency signals containing time and orbit information of said satellites, a method of acquiring said satellite signals at a receiver, the method comprising:
-
receiving a satellite signal at the receiver; performing short-length correlations between the received satellite signal and locally generated reference codes, wherein each short-length correlation spans approximately 1 ms; performing block accumulating coherent integration of said short-length correlations over a preset extended length, wherein performing the block accumulating coherent integration includes; reducing frequency error for a block of short-length correlations prior to integrating said block with preceding blocks over said preset extended length; adding said frequency error reduced block of short-length correlations to partial sums of previous blocks of short-length correlations, thereby updating said partial sums, wherein each partial sum is added for a different possible data bit edge and a corrected bit sign of said block; and making a decision based upon said updated partial sums to ascertain the presence or absence of said satellite signal up to this point. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
-
15. A receiver including:
-
an antenna capable of coupling to signals transmitted from a plurality of satellites of the Global Navigation Satellite System; a radio frequency front-end that receives said signals from said satellites via said antenna, wherein said radio frequency front-end comprises a bandpass filter, power amplifier, and frequency down-converter; a baseband signal processor comprising signal acquisition and tracking circuitry containing a plurality of functionally identical channels for extracting navigation data bits and other time and frequency parameters from said signals using said functionally identical channels; and a data processor for calculating a navigation solution from said extracted navigation data bits and other time and frequency parameters; wherein the baseband signal processor dynamically assigns said signals to the functionally identical channels such that distinct signals are assigned to distinct channels, and wherein each of the functionally identical channels performs weak signal acquisition using a block-accumulating coherent integrator for coherently adding successive blocks of consecutive short-length correlations over a desired extended length for different possible tentative data bit transitions with tentative bit transition and sequence of data bits dynamically estimated, wherein each short-length correlation spans approximately 1 ms. - View Dependent Claims (16, 17, 18, 19, 20)
-
Specification