Abstract: A Global Positioning System receiver incorporating a method of reducing the effect of common mode oscillator phase noise. Oscillator phase noise in the receiver is a basic limitation on narrowing the carrier tracking loop bandwidth and, therefore, on the achievable carrier-track C/No for a GPS receiver tracking a single satellite signal. However, when receiving several satellite signals, the receiver phase noise is common to all tracking loops and, in principle, can be removed by a common-mode rejection scheme. The phase noise contributed by the satellites is negligible in comparison with the phase noise contributed by the receiver's oscillator; hence, the common-mode rejection is improved by tracking multiple satellite signals.
Abstract: A GPS car navigation system derives GPS position update information from motion of the car along the actual track. Turns along the track are detected when they actually occur and are compared with the predicted turns so that the time and position at the actual turn can be used to update the then current GPS derived position of the vehicle. Updating position information with actual turn data improves the accuracy of GPS navigation especially during single satellite navigation.
Abstract: The compact voltage controlled ring oscillator includes two variable delay gates (VDGs). Each input port of one variable delay gate is connected to the output port of the other variable delay gate to form a feedback loop. A control interface receives an input voltage control signal (VCON), and generates a limited and buffered voltage control signal VX, which is provided to each of the VDGs to generate VDG bias currents which are limited and monotonic with VCON. Each VDG comprises a fixed bias differential transconductance gain stage (GM1), a variable bias differential transconductance hysteresis feedback stage (GM2), and a variable bias voltage follower stage. The combination of delay control from variable hysteresis and variable voltage follower output resistance provides a compact, low power ring oscillator VCO, with over an octave of tuning range.
Abstract: A GPS car navigation system permits single satellite navigation by representing the x and y unknowns with on-track and cross track vectors and estimating the z and t unknowns. An estimate of the y unknown, representing the maximum width of the track or roadway, is thereby combined with altitude and clock hold estimates to derive GPS position information along the predicted track. Turns along the track are detected when they actually occur and are compared with the predicted turns so that the time and position at the actual turn can be used to update the then current GPS derived position of the vehicle. Updating position information with actual turn data improves the accuracy of GPS navigation especially when using single satellite navigation.
Abstract: A spread spectrum receiver, such as a GPS car navigation system, uses multiple, parallel correlations of data in a wide capture window, permits seamless tracking and rapid reacquisition of satellite signals at speeds sufficient to permit position information updates during momentary views available of satellites in intersections. The received data is processed in 11 bit samples, for a total of 186 time segments per 1 msec code period, which are each Doppler shifted and multiplexed into 12 channels. The code correlations are performed 22 times per channel by shifting the 11 bit locally generated code by one bit each correlation. The chip rate of the incoming data is 2f.sub.0 and the correlations are performed at 48f.sub.0 providing a time magnification advantage of 24.