Abstract: According to certain aspects, the invention includes using acquisition channel results from a number of satellites to achieve composite weak acquisition. According to certain other aspects, the invention also includes solving for an improved position estimate and, with a sufficiently accurate, either initial or improved position estimate, also solving for GPS system time using a composite of acquired signals from a plurality of satellites. Within commonly experienced initial position and time uncertainties, the geometric range changes are fairly linear, which allows the point of convergence of ranges to solve for GPS position and subsequently for time with reasonable accuracy, which is the equivalent to obtaining frame sync without any data demodulation or preamble matching.

Abstract: A method for soft frame synchronization in a navigational receiver is provided. A distance between bits of a sync pattern received by the navigational receiver and a known sync pattern is computed. A probability of detection value for the received sync pattern based on the distance is assigned. A confidence level for the received sync pattern using the probability of detection value is computed. The confidence level is compared with a confidence threshold. If the confidence level is greater than or equal to the confidence threshold, the confidence level of the received sync pattern is updated to generate a credibility of the sync pattern. The credibility of the received sync pattern is compared with a predetermined credibility value and, if the credibility of the received sync pattern is greater than or equal to the predetermined credibility value, synchronization of the navigational receiver is performed using the received sync pattern.

Abstract: Methods, systems, and apparatuses for a portable device capable of receiving satellite navigational system signals to retrieve visibility mask information corresponding to the portable device's current location and/or trajectory are described.

Abstract: A method for soft frame synchronization in a navigational receiver is provided. A distance between bits of a sync pattern received by the navigational receiver and a known sync pattern is computed. A probability of detection value for the received sync pattern based on the distance is assigned. A confidence level for the received sync pattern using the probability of detection value is computed. The confidence level is compared with a confidence threshold. If the confidence level is greater than or equal to the confidence threshold, the confidence level of the received sync pattern is updated to generate a credibility of the sync pattern. The credibility of the received sync pattern is compared with a predetermined credibility value and, if the credibility of the received sync pattern is greater than or equal to the predetermined credibility value, synchronization of the navigational receiver is performed using the received sync pattern.

Abstract: Methods, systems, and apparatuses for a portable device capable of receiving satellite navigational system signals to retrieve visibility mask information corresponding to the portable device's current location and/or trajectory are described.

Abstract: According to certain aspects, the invention includes using acquisition channel results from a number of satellites to achieve composite weak acquisition. According to certain other aspects, the invention also includes solving for an improved position estimate and, with a sufficiently accurate, either initial or improved position estimate, also solving for GPS system time using a composite of acquired signals from a plurality of satellites. Within commonly experienced initial position and time uncertainties, the geometric range changes are fairly linear, which allows the point of convergence of ranges to solve for GPS position and subsequently for time with reasonable accuracy, which is the equivalent to obtaining frame sync without any data demodulation or preamble matching.

Abstract: A communication device with cross-correlation detection based upon statistical tests to determine whether the off-peak signal energy is consistent with auto-correlation energy levels.

Abstract: Memory reallocation and sharing among components of an electronic system is provided. The electronic system includes a first memory area coupled for access by a first processor via a first bus, and a second memory area coupled for access by a second processor via a second bus. An example system includes a central processor as the first processor and a digital signal processor as the second processor. The electronic system further includes memory configurations that support shared access of the second memory area by the first processor. Using shared access, the first processor can directly access the second memory via the first bus or indirectly access the second memory via the second bus and the second processor. The memory sharing also includes partitioning the shared memory to simultaneously provide the first processor with direct and indirect access to the shared memory.

Abstract: A system is provided for storing positional data received from GPS signals in response to an event, and then processing that positional data at a later time to obtain detailed location information of the system at the time of the event. The received GPS signals may be decimated to a desired sampling rate and then stored for later correlation. In one embodiment, the system is a digital camera having an antenna, an RF front end, and a non-volatile memory device. The event which triggers the storage of the positional data is a photo capture by the digital camera. The positional data, in decimated but uncorrelated form, is stored with the image data in the non-volatile memory device. The positional data can then be transferred with the image data to a separate device, such as a personal computer, for post-processing.

Abstract: A method and apparatus for real time clock brownout detection. A low power real time clock (RTC) operates continuously to keep time in a global positioning system (GPS) receiver while some receiver components are powered down. In various embodiments, a brownout detector circuit detects a loss of RTC clock cycles. If a loss of RTC clock cycles exceeds a predetermined threshold such that the RTC is not reliable for GPS navigation, an RTC status signal so indicates.

Abstract: An Edge-Aligned Ratio Counter (EARC) that includes at least one processor coupled to at least one counter circuit is provided for determining a ratio between two clock signals by receiving a first and a second value in response to a first clock signal and generating a control signal under control of the loaded value by counting the pulses of the first clock signal and a second clock signal and captures the count of each clock signal in response to the control signal and determining a ratio between a frequency of the first clock signal and a frequency of the second clock signal using the differences of the captured counts taken at two different occurrences of the control signal.

Abstract: A data detection circuit within a global positioning system (GPS) satellite receiver operates to detect and decode data sent in a spread spectrum signal. The data detection circuit receives input from a radio receiver, the information containing data from a plurality of satellites. The data is supplied to a circular memory device, which determines which data corresponds to which satellite. The memory device sends the received signal to a matched filter, which decodes the signal received from each satellite. This signal is analyzed to determine whether a phase inversion due to data modulation on the received signal is present. The phase inversion can occur at boundaries, known as data epochs, in the received signal, and corresponds to data in the received signal. This data contains information relating to the position of each satellite and is collected by the data detection circuit for use by the GPS receiver.

Abstract: A frequency phase correction system and method are described that provides a receiver with a greater ability to lock onto relatively weak radio frequency signals by determining and estimating an amount of frequency error in a local frequency reference of the receiver, and using the error estimate to maintain frequency coherence with a received signal, thereby allowing tracking over a longer period of time, enabling longer integration times to capture weaker signals without losing frequency coherence.

Abstract: A signal detector is provided in which complex samples of a received signal are multiplied by data representative of a hypothesis, and the resulting product data is coherently integrated over a desired duration to provide correlation data representative of the level of correlation between the hypothesis and the signal. In one embodiment, the signal detector is part of a GPS receiver.

Abstract: Memory reallocation and sharing among components of an electronic system is provided. The electronic system includes a first memory area coupled for access by a first processor via a first bus, and a second memory area coupled for access by a second processor via a second bus. An example system includes a central processor as the first processor and a digital signal processor as the second processor. The electronic system further includes memory configurations that support shared access of the second memory area by the first processor. Using shared access, the first processor can directly access the second memory via the first bus or indirectly access the second memory via the second bus and the second processor. The memory sharing also includes partitioning the shared memory to simultaneously provide the first processor with direct and indirect access to the shared memory.

Abstract: A signal detector is provided in which correlation analyses of multiple segments of a received signal from separate and distinct periods of time are combined to improve the detection capability of the signal detector. In one embodiment, the signal detector is part of a GPS receiver.

Abstract: A cancellation system may utilize a system architecture that delays the received signals and cancels less than all the received signals from the delayed version of the received signals. An implementation of this system architecture may include a delay circuit, a demodulation and despreader unit, a re-modulator and re-spreader unit and a combiner. The delay circuit produces a delayed version of the received signals and the demodulator and de-spreader unit produces a demodulated and de-spread signal corresponding to one of the received signals. The respreader and remodulator unit produces a remodulated and respread signal from the demodulated and despread signal and the combiner produces a combined signal from the delayed version of the received signals and the remodulated and respread signal. The cancellation system may also utilize a system architecture that stores the received signals and cancels less than all the received signals from the stored version of the received signals.

Abstract: A signal detector is provided in which complex samples of a received signal are multiplied by data representative of a hypothesis, and the resulting product data is coherently integrated over a desired duration to provide correlation data representative of the level of correlation between the hypothesis and the signal. In one embodiment, the signal detector is part of a GPS receiver.