| Method and apparatus for receiving gps/glonass signals -> Monitor Keywords |
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Method and apparatus for receiving gps/glonass signalsRelated Patent Categories: Pulse Or Digital Communications, Spread Spectrum, Direct Sequence, Receiver, Correlation-type ReceiverMethod and apparatus for receiving gps/glonass signals description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060098721, Method and apparatus for receiving gps/glonass signals. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a continuation application which claims priority under 35 U.S.C. .sctn.120 from U.S. patent application Ser. No. 11/139,128, filed May 26, 2005, and which is incorporated by reference. U.S. patent application Ser. No. 11/139,128 also claimed priority from U.S. patent application Ser. No. 09/196,658, filed Nov. 19, 1998, now U.S. Pat. No. 6,967,992, issued Nov. 22, 2005, and which is also incorporated by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an electronic system and its components and to methods of operating the system and its components for receiving spread spectrum signals, for example, signals from a global positioning system such as Global Positioning System (GPS) and/or Global Orbiting Navigation Satellite System (GLONASS). [0004] 2. Description of the Related Technology [0005] An increasing number of applications and systems for communicating information nowadays make use of the spread spectrum technique. The spread spectrum technique is a digital modulation technique in which a digital signal is spread over a wide frequency band so that it has a noise-like spectrum. This can be done by breaking up or "chopping" each data bit of the digital signal into multiple sub-bits (commonly called chips) that are then modulated and up-converted to a carrier frequency. The chopping may be done by multiplying the digital information signal with a so-called pseudo-random code or PN code. By using orthogonal codes for different communication links, the same frequency band can be used for different simultaneous communication links. [0006] Using the same PN code as the transmitter, a receiver can correlate the received, spread signal and reconstruct the data signal while other receivers that use other codes or other transmission techniques cannot. One of the advantages of using the spread spectrum communication technique is the robustness to narrow band interference signals. Because spread-spectrum receivers are rapidly being introduced in applications and systems meant for the consumer markets, the cost of the receiver system is a major determining factor in order to remain competitive. [0007] A specific class of spread spectrum systems are devices and receivers for position determination. Such devices are gaining importance for both the consumer market and for high precision applications. Most of the existing systems are based on the American Global Positioning System (GPS). Because this is also a military system, a precise position determination can be made difficult by the satellite operator deliberately introducing errors (called "anti-spoofing"). Moreover, in many areas the number of visible satellites can be too limited to determine an accurate position. These two problems can be reduced by also using a second positioning system such as the Russian Global Orbiting Navigation Satellite System (GLONASS) system. [0008] Combined GPS and GLONASS receivers have been reported, e.g., S. Riley, N. Howard, E. Aardoom, R. Daly, and P. Silvestrin, in "A combined GPS/GLONASS high precision receiver for space applications," ION-GPS 95, Palm Springs, USA, September 1995, or Japanese patent application JP 7128423-950519, "Receiver Common to GPS and GLONASS." [0009] A GPS receiver is disclosed in U.S. Pat. No. 5,293,170 that can be used with P-code modulated signals, which have been modulated with an unknown code. Implementations of this known device require a lot of registers. [0010] U.S. Pat. No. 5,600,670 describes a GPS receiver that includes a hierarchical chain of channel modules which includes slave modules and a master module. The known system does not provide sufficient flexibility. SUMMARY OF CERTAIN INVENTIVE ASPECTS [0011] One aspect of the invention provides a method of processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random code modulated thereon, each L1 and L2 signal being converted into a plurality of digital signals, the method comprising: i) locally generating a single replica of the known code, ii) making the code replica available at different relative phases, iii) first demodulating the converted L1 and L2 signals with the single replica of the known code without any substantial delay, the first demodulated signal being associated with the L1 signal, iv) second demodulating the converted L1 and L2 signals with the generated replica of the known code from one of the taps of the delay line, the second demodulated signal being associated with the L2 signal, v) selectably switching the converted L1 and L2 signals for the first demodulation and selectably switching the converted L1 and L2 signals for the second demodulation, vi) repetitively and separately integrating the demodulated L1 and L2 signals over a time period, and vii) adjusting the phases of the locally generated code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the integrated demodulated L1 and L2 signals. [0012] Another aspect of the invention provides an apparatus for processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, the apparatus comprising: i) a generator of replicas of the known P-code, ii) a delay line configured to make the known P-code replicas available at different relative phases, iii) a first demodulator, connected to the generator, configured to demodulate one of the received L1 and L2 signals with one of the known P-code replicas, iv) a second demodulator configured to demodulate the other of the received L1 and L2 signals with one of the known P-code replicas, v) a first integrator configured to repetitively and separately integrate the demodulated one of the L1 and L2 signals over time periods related to the unknown code, vi) a second integrator configured to repetitively and separately integrate the demodulated other of the L1 and L2 signals over time periods related to the unknown code, and vii) a correlator configured to correlate the first integrator output with the second integrator output. [0013] Another aspect of the invention provides an apparatus for processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random code modulated thereon, each L1 and L2 signal being converted into a plurality of digital signals, the apparatus comprising: i) a generator configured to locally generate a single replica of the known code, ii) a delay line wherefrom the known P-code replicas are available at different relative phases thereof, wherein the single replica of the known code is applied to the delay line, iii) a first demodulator configured to first demodulate the converted L1 and L2 signals with the single replica of the known code without any substantial delay, the first demodulated signal being associated with the L1 signal, iv) a second demodulator configured to second demodulate the converted L1 and L2 signals with the generated replica of the known code from one of the taps of the delay line, the second demodulated signal being associated with the L2 signal, v) a switch configured to selectably switch the converted L1 and L2 signals for the first demodulation and selectably switch the converted L1 and L2 signals for the second demodulation, vi) an integrator configured to repetitively and separately integrate the demodulated L1 and L2 signals over a time period, and vii) a phase adjuster configured to adjust the phases of the locally generated code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the integrated demodulated L1 and L2 signals. [0014] Still another aspect of the invention provides a method of processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, the method comprising: i) locally generating replicas of the known P-code, ii) making the code replicas available at different relative phases, iii) demodulating the received L1 and L2 signals with replicas of the P-code, iv) repetitively and separately integrating the demodulated L1 and L2 signals over time periods related to the unknown code, and v) correlating an integration result for one of the L1 and L2 signals with an integration result for the other of the L1 and L2 signals. BRIEF DESCRIPTION OF THE DRAWINGS [0015] FIG. 1 is a schematic block diagram showing the major components of a spread spectrum receiver according to one embodiment of the present invention. [0016] FIG. 2 illustrates a schematic representation of a part of the correlator unit in accordance with one embodiment of the present invention. [0017] FIG. 3 illustrates a schematic representation of a channel matrix in accordance with an embodiment of the present invention. [0018] FIG. 4 illustrates a schematic representation of a CA-channel module in accordance with an embodiment of the present invention. [0019] FIG. 5 illustrates a schematic representation of a hierarchical chain of CA-channel modules in accordance with an embodiment of the present invention. [0020] FIG. 6 illustrates a schematic representation of a dual frequency channel in accordance with an embodiment of the present invention. Continue reading about Method and apparatus for receiving gps/glonass signals... 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