Method and apparatus for digital processing in a global positioning system receiver
First Claim
1. A method of processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said method comprising the steps of:
- demodulating each of the received L1 and L2 signals with a locally generated replica of their respective carrier signals and with locally generated replicas of the known P-code that is contained therein to generate first and second modulated L1 signals and first and second demodulated L2 signals;
separately integrating the first and second demodulated L1 signals and the first and second demodulated L2 signals over a time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals and first and second integrated demodulated L2 signals;
correlating the second integrated demodulated L1 signal with said second integrated demodulated L2 signal in order to provide a correlated L2 signal, and correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 tracking signal, andadjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L1 tracking signal and upon said correlated L2 signal, said locally generated carrier and P-code phases being useable to recover at least said unique L2 frequency carrier with favorable signal to noise ratio.
5 Assignments
0 Petitions
Accused Products
Abstract
A Global Positioning System (GPS) commercial receiver including a digital processor disposed to utilize the energy of both the L1 and L2 GPS satellite signals in order to derive an estimate of an unknown security code used to modulate the signals. In processing the signal energy from the received L1 and L2 signals in accordance with statistical Maximum A Posteriori (MAP) estimation theory, the received L1 signal is correlated with a locally generated replica of the P-code, and passed through a bandpass filter having a bandwidth approximating the bandwidth of the unknown modulation code. The received L2 signal is similarly correlated and filtered, and the decorrelated signals are then latched in such a way as to account for the differential ionospheric refraction of the L1 and L2 signals. The bandlimited L2 signal is used to produce quadrature error signals related to phase difference between the L2 signal and a locally generated L2 replica. The error signals are integrated over an integration period which approximates the bit period of the unknown code, with the resulting estimates of the bits of the unknown code being combined with corresponding L1 channel code bit estimates weighted by a factor proportional to the difference in received L1 and L2 signal power. The hyperbolic tangent of each combined W-code bit estimate is then computed, with the result being multiplied by one of the integrated error signals. The resulting control voltage is then used to adjust the locally generated L2 carrier phase.
85 Citations
30 Claims
-
1. A method of processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said method comprising the steps of:
-
demodulating each of the received L1 and L2 signals with a locally generated replica of their respective carrier signals and with locally generated replicas of the known P-code that is contained therein to generate first and second modulated L1 signals and first and second demodulated L2 signals; separately integrating the first and second demodulated L1 signals and the first and second demodulated L2 signals over a time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals and first and second integrated demodulated L2 signals; correlating the second integrated demodulated L1 signal with said second integrated demodulated L2 signal in order to provide a correlated L2 signal, and correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 tracking signal, and adjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L1 tracking signal and upon said correlated L2 signal, said locally generated carrier and P-code phases being useable to recover at least said unique L2 frequency carrier with favorable signal to noise ratio. - View Dependent Claims (2, 3, 4, 5, 6)
-
-
7. A method of processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said method comprising the steps of:
-
demodulating each of the received L1 and L2 signals with a locally generated replica of their respective carrier signals and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals and first and second demodulated L2 signals; separately integrating the first and second demodulated L1 signals and the first and second demodulated L2 signals over a time period equal in length to a plurality of P-code cycles, to generate first and second integrated demodulated L1 signals and first and second integrated demodulated L2 signals; correlating the first integrated demodulated L1 signal with the second integrated demodulated L1 signal in order to provide a correlated L1 signal, and correlating the second integrated L1 signal with the first integrated demodulated L2 signal in order to generate an L2 tracking signal, and adjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L2 tracking signal and upon said correlated L1 signal, said locally generated carrier and P-code phases being useable to recover at least said unique L1 frequency carrier.
-
-
8. A method of processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said method comprising the steps of:
-
demodulating the received L1 signal with a locally generated replica of its respective carrier signal and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals; demodulating the received L2 signal with a locally generated replicas of the known P-code contained therein to generate first and second pre-demodulated L2 signals.; separately integrating the first and second demodulated L1 signals over a predefined time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals; correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 P-code track signal; providing said first and second pre-demodulated L2 signals and said second integrated demodulated L1 signal to a feedback loop network operative to generate an estimate of said L2 carrier signal in response thereto; and adjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L1 P-code track signal and said estimate of said L2 carrier signal, said phases of said locally generated carrier signal and P-code replicas being useable to recover at least said unique L2 frequency carrier. - View Dependent Claims (9, 10, 11, 12)
-
-
13. A method of processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said method comprising the steps of:
-
demodulatina the received L1 signal with a locally generated replica of its respective carrier signal and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals; demodulating the received L2 signal with a locally generated replicas of the known P-code contained therein to generate first and second pre-demodulated L2 signals; separately integrating the first and second demodulated L1 signals over a predefined time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals; separately correlating the first pre-demodulated L2 signal with estimates of in-phase and quadrature-phase L2 carrier signals, separately integrating the results of the separate correlations over said predefined time period to generate first and second integrated demodulated L2 signals, and, based upon a predefined function of said first and second integrated demodulated L2 signals in combination with said second integrated demodulated L1 signal, providing said estimates of in-phase and quadrature-phase L2 carrier signals; correlating the second pre-demodulated L2 signal with the estimate of the in-phase L2 carrier signal and integrating the result to generate a third integrated demodulated L2 signal; correlating the third integrated demodulated L2 signal with the second integrated demodulated L1 signal in order to provide an L2 P-code track signal, and correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 P-code track signal; and adjusting the phases of the P-code replicas relative to the received L1 and L2 signals based upon said L1 and L2 P-code track signals. - View Dependent Claims (14, 15)
-
-
16. A receiver for processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said receiver comprising:
-
means for demodulating each of the received L1 and L2 signals with a locally generated replica of their respective carrier signals and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals and first and second demodulated L2 signals; means for separately integrating the first and second demodulated L1 signals and the first and second demodulated L2 signals over a time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals and first and second integrated demodulated L2 signals; first means for correlating the second integrated demodulated L1 signal with said second integrated demodulated L2 signal in order to provide a correlated L2 signal, and second means for correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 tracking signal; and phase adjusting means for adjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L1 tracking signal and upon said correlated L2 signal, said locally generated carrier and P-code phases being useable to determine location of said receiver. - View Dependent Claims (17, 18, 19, 20, 21)
-
-
22. A receiver for processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said receiver comprising:
-
means for demodulating each of the received L1 and L2 signals with a locally generated replica of their respective carrier signals and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals and first and second demodulated L2 signals; means for separately integrating the first and second demodulated L1 signals and the first and second demodulated L2 signals over a time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals and first and second integrated demodulated L2 signals; first means for correlating the first integrated demodulated L1 signal with the second integrated demodulated L1 signal in order to provide a correlated L1 signal, and second means for correlating the second integrated L1 signal with the second integrated demodulated L2 signal in order to generate an L2 tracking signal, and means for adjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L2 tracking signal and upon said correlated L1 signal.
-
-
23. A receiver for processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said receiver comprising:
-
means for demodulating the received L1 signal with a locally generated replica of its respective carrier signal and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals; means for demodulating the received L2 signal with a locally generated replicas of the known P-code contained therein to generate first and second pre-demodulated L2 signals means for separately integrating the first and second demodulated L1 signals over a predefined time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals; means for correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 P-code track signal; means for providing said first and second pre-demodulated L2 signals and said second integrated demodulated L1 signal to a feedback loop network operative to generate an estimate of said L2 carrier signal in response thereto; and means for adjusting the phases of the locally generated carrier signal and P-code replicas relative to the received L1 and L2 signals based upon said L1 P-code track signal and upon said estimate of said L2 carrier signal. - View Dependent Claims (24, 25, 26, 27)
-
-
28. A receiver for processing L1 and L2 signals received in a global positioning system (GPS), each of said L1 and L2 signals including a unique frequency carrier with a known pseudo-random P-code and unknown code modulated thereon, said receiver comprising:
-
means for demodulating the received L1 signal with a locally generated replica of its respective carrier signal and with locally generated replicas of the known P-code contained therein to generate first and second demodulated L1 signals; means for demodulating the received L2 signal with a locally generated replicas of the known P-code contained therein to generate first and second pre-demodulated L2 signals; means for separately integrating the first and second demodulated L1 signal over a predefined time period equal in length to a plurality of P-code cycles to generate first and second integrated demodulated L1 signals; means for separately correlating the first pre-demodulated L2 signal with estimates of in-phase and quadrature-phase L2 carrier signals, for separately integrating the results of the separate correlations over said predefined time period to generate first and second integrated demodulated L2 signals, and, based upon a predefined function of said first and second integrated demodulated L2 signals in combination with said second integrated demodulated L1 signal, for providing said estimates of the in-phase and quadrature-phase L2 carrier signals; means for correlating the second pre-demodulated L2 signal with the estimate of the in-phase L2 carrier signal integrating the result to generate a third integrated demodulated L2 signal; means for correlating the third integrated demodulated L2 signal with the second integrated demodulated L1 signal in order to provide an L2 P-code track signal, and for correlating the second integrated demodulated L1 signal with the first integrated demodulated L1 signal in order to generate an L1 P-code track signal; and means for adjusting the phases of the P-code replicas relative to the received L1 and L2 signals based upon said L1 and L2 P-code track signals. - View Dependent Claims (29, 30)
-
Specification