| SiRF TECHNOLOGY HOLDINGS, INC. Patent applications |
| Patent application number | Title | Published |
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| 20110193742 | Method and Apparatus for Weak Data Frame Sync in a Positioning System - The present invention is related to location positioning systems, and more particularly, to a method and apparatus of synchronizing to data frames in a positioning system signal. According to one aspect, the invention speeds up the frame synchronization process by computing a frame synchronization metric for each satellite and then combining together the metrics for all tracked satellites together, after compensating for respective signal transit times. Then the invention makes a frame sync decision on the combined satellite metric. In embodiments, an optimal combining algorithm is used based on CNO of each satellite. According to further aspects, the invention further speeds up the frame synchronization process by predicting many bits in the subframe so that more bits are known in addition to the 8-bit preamble. For example, the invention recognizes that many bits in a subframe rarely change or don't change very often. Moreover, the invention uses old ephemeris used to predict new ephemeris parameters. These parameters are translated into predicted bits in the signal. Still further, old ephemeris can be used to predict almanac parameters, and the almanac can be used to predict ephemeris parameters. | 08-11-2011 |
| 20110184645 | USE OF ACCELEROMETER ONLY DATA TO IMPROVE GNSS PERFORMANCE - The present invention provides apparatus and methods for improving satellite navigation by assessing the dynamic state of a platform for a satellite navigation receiver and using this data to improve navigation models and satellite tracking algorithms. The dynamic state of the receiver platform may be assessed using only accelerometer data, and does not require inertial navigation system integration. The accelerometers may not need to be very accurate and may not need to be aligned and/or accurately calibrated. A method of accelerometer assisted satellite navigation may comprise: detecting a stationary condition of an accelerometer set; gross-calibrating the accelerometer set when in the stationary condition, wherein gross-calibrating includes determining a combined-bias of the accelerometer set; defining at least two acceleration levels using the combined-bias; collecting accelerometer data; categorizing the accelerometer data into one of the acceleration levels; and utilizing the categorized accelerometer data to enhance satellite navigation. | 07-28-2011 |
| 20110077891 | ACCELEROMETER-ONLY CALIBRATION METHOD - Methods for calibrating an accelerometer without needing to use external assistance signals, such as GNSS signals. The invention is applicable to accelerometers generally—in both GPS navigation devices and other devices. A method of calibrating an accelerometer, the accelerometer having a bias, comprises: rotating the accelerometer, wherein the orientation of the axis of the accelerometer changes with respect to the local gravity vector; collecting accelerometer measurements as the accelerometer is moving; and calculating the bias and/or scale factor; wherein the accelerometer measurements are primarily due to local gravity. Furthermore, some embodiments of the present invention include a self-calibration process—a process that does not engage the user's attention. For example, in a self-calibration process for an accelerometer in a cell phone the moving step may be the movement of the phone out of a user's pocket to hold it up to view the screen. | 03-31-2011 |
