Abstract: A method and device to acquire navigational satellite signals combines non-coherent and coherent integrations and can efficiently acquire both strong and weak signals. Successive steps eliminate lower powered and less likely combinations of code offsets and carrier frequencies or dwells of a given satellite signal. Only remaining dwells then are correlated and integrated over larger time duration to obtain the most probable dwell or dwells, which results in reduced computational load. The selection of most likely dwells is based on Parseval's theorem on equivalence of power in time and frequency domains. An optimal estimator algorithm efficiently estimates the probable navigation data bits embedded in the received signal. In case of an ambiguity due to several possible dwells, the steps are repeated with a new set of signal samples.

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.

Abstract: The invention provides a method and apparatus to optimally estimate and adaptively compensate the temperature-induced frequency drift of a crystal oscillator in a navigational signal receiver. A Read-Write memory encodes two tables, one for looking up frequency drift values versus temperature readings and another one for valid data confirmation on the first table. The initially empty look-up table is gradually populated with frequency drift values while the receiver computes the frequency drift along with its position. During initial start of the receiver or re-acquisition of satellite signals, the stored frequency drift value corresponding to the current temperature is used. If no valid frequency drift value is available, the frequency drift value is computed based on the existing frequency drift values in the table. This invention reduces the Time-To-First-Fix (TTFF) of the receiver and enables the receiver to self-calibrate, thus no additional factory calibration would be necessary.

Abstract: The present invention provides a new baseband integrated circuit (IC) architecture for direct sequence spread spectrum (DSSS) communication receivers. The baseband IC has a single set of baseband correlators serving all channels in succession. No complex parallel channel hardware is required. A single on-chip code Numerically Controlled Oscillator (NCO) drives a pseudorandom number (PN) sequence generator, generates all code sampling frequencies, and is capable of self-correct through feedback from an off-chip processor. A carrier NCO generates corrected local frequencies. These on-chip NCOs generate all the necessary clocks. This architecture advantageously reduces the total hardware necessary for the receiver and the baseband IC thus can be realized with a minimal number of gate count. The invention can accommodate any number of channels in a navigational system such as the Global Positioning System (GPS), GLONASS, WAAS, LAAS, etc.

Abstract: The present invention provides a method and apparatus for a satellite navigation receiver to lock onto satellite signals in the cold start mode with no information on the receiver position, the satellite position, or time estimates stored in the receiver's memory. All satellites in a positioning system are divided into groups based on the satellite constellation structure. In an embodiment, the positioning system is the Global Positioning System (GPS) and all GPS satellites are divided into three groups. During initialization of the receiver, the satellites are searched per group to lock onto at least one satellite signal. Other satellites are then searched in a given order based on their respective distance or proximity to the first satellite acquired. This method reduces the Time-to-First-Fix (TTFF) ordinarily required by conventional receivers in the cold start mode.