Adaptive correlation for detection of a high-frequency signal

#An embodiment of the invention relates generally to a receiver for processing and detection of a high-frequency received signal, such as a satellite navigation signal, and a related method.

#Satellite navigation has become a prerequisite for a wide range of electronic positioning devices that include products intended for vehicular and portable applications. As a result, deep urban and indoor areas are becoming increasingly important for emerging satellite navigation designs. Attenuation, shadowing, and multipath fading effects in urban canyons and indoor areas frequently degrade the received satellite navigation signals. Signal obstructions in these environments often lead to limited service availability.

#A navigation system in use today for determining a position of a mobile radio receiver may utilize the satellite-based GPS system, and in the near future, the European Galileo system. The terms “GPS” and “Galileo” are used interchangeably herein. Both systems work similarly, each employing about 24 to 31 orbiting satellites, each satellite with accurately known position and time that transmit a signal with a time stamp that indicates when the signal was sent from the satellite. In order to be able to compute the position of the mobile receiver, satellite clocks in each system are accurately synchronized to a common time reference. The mobile receiver calculates its position by the following (simplified) steps: First the time stamp of at least four satellites is extracted from received signals by the mobile receiver, and the time of arrival of the time-stamped message is recorded. The distance from each satellite to the mobile receiver is calculated by comparing the respective time stamp with its arrival time, using the accurately known propagation velocity of the radio signal. The position of each satellite can be accurately determined at any instant in time by the mobile receiver using satellite ephemeris data, which is regularly updated and transmitted by the satellites. Thus, the distance to at least three of the satellites can be calculated by the mobile receiver position using triangulation. However, the clock in the mobile receiver may not be accurately synchronized with the synchronized clocks in the satellites. A time-stamped signal received from a fourth satellite by the mobile receiver is generally used to compensate clock uncertainty in the mobile receiver. To improve accuracy even further in determining the location of the mobile receiver, perturbation effects operative on the received signal such as atmospheric effects, earth rotation, relativity, etc., are typically included in the computation of the mobile receiver location.

#The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. In the figures, identical reference symbols generally designate the same component parts throughout the various views, and may be described only once in the interest of brevity. For a more complete understanding of the invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

#FIG. 1 illustrates a signal flow diagram for a receiver with adaptive correlation, constructed according to an embodiment;

#FIGS. 2A-2D illustrate graphs showing reception sensitivity for the adaptive integration technique versus observation time for a receiver constructed according to an embodiment; and

#The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.

#The present invention will be described with respect to exemplary embodiments in a specific context, namely a process and method to provide improved signal detection capability for an RF (radio frequency) signal such as a GPS or Galileo satellite signal.

#An embodiment of the invention may be applied to various signal-detection arrangements in a high-frequency receiver, for example, to a cellular telephone receiver. Other signal-detection arrangements can be constructed and applied using processes introduced herein in different contexts using inventive concepts described herein, for example, a signal detection arrangement employed to detect a high-frequency modulated carrier signal that might be transmitted over an air or a hard-wired channel to a receiver in a local area network or to a television broadcast receiver.