P-code enhanced method for processing encrypted GPS signals without knowledge of the encryption code
First Claim
1. A receiver for processing a received signal transmitted as an L1 or an L2 signal comprised of a single carrier modulated by a known code and by an unknown code wherein said unknown code causes adverse effects, said receiver comprising:
- means for converting said L1 or L2 signal to quadrature components;
means for generating a model for said carrier;
means for generating a model for said known code;
means for counter-rotating said quadrature components of said L1 or L2 signal with said model carrier to produce counter-rotated signals;
means for correlating said model code with said counter-rotated signals to produce at least one correlation product separately for each counter-rotated signal;
means for accumulating said correlation products successively over selected time intervals;
means for combining with one another said accumulated correlation products derived from said quadrature components of said L1 or L2 signal in a manner reducing said adverse effects of said unknown code; and
,means for generating an amplitude factor whereby said combined accumulated correlation products and amplitude factor are used to extract said signal'"'"'s amplitude, phase, and delay, in the presence of said unknown code.
1 Assignment
0 Petitions
Accused Products
Abstract
In the preferred embodiment, an encrypted GPS signal is down-converted from RF to baseband to generate two quadrature components for each RF signal (L1 and L2). Separately and independently for each RF signal and each quadrature component, the four down-converted signals are counter-rotated with a respective model phase, correlated with a respective model P code, and then successively summed and dumped over presum intervals substantially coincident with chips of the respective encryption code. Without knowledge of the encryption-code signs, the effect of encryption-code sign flips is then substantially reduced by selected combinations of the resulting presums between associated quadrature components for each RF signal, separately and independently for the L1 and L2 signals. The resulting combined presums are then summed and dumped over longer intervals and further processed to extract amplitude, phase and delay for each RF signal. Precision of the resulting phase and delay values is approximately four times better than that obtained from straight cross-correlation of L1 and L2. This improved method provides the following options: separate and independent tracking of the L1-Y and L2-Y channels; separate and independent measurement of amplitude, phase and delay L1-Y channel; and removal of the half-cycle ambiguity in L1-Y and L2-Y carrier phase.
-
Citations
23 Claims
-
1. A receiver for processing a received signal transmitted as an L1 or an L2 signal comprised of a single carrier modulated by a known code and by an unknown code wherein said unknown code causes adverse effects, said receiver comprising:
-
means for converting said L1 or L2 signal to quadrature components; means for generating a model for said carrier; means for generating a model for said known code; means for counter-rotating said quadrature components of said L1 or L2 signal with said model carrier to produce counter-rotated signals; means for correlating said model code with said counter-rotated signals to produce at least one correlation product separately for each counter-rotated signal; means for accumulating said correlation products successively over selected time intervals; means for combining with one another said accumulated correlation products derived from said quadrature components of said L1 or L2 signal in a manner reducing said adverse effects of said unknown code; and
,means for generating an amplitude factor whereby said combined accumulated correlation products and amplitude factor are used to extract said signal'"'"'s amplitude, phase, and delay, in the presence of said unknown code. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
-
-
19. A receiver for processing a received L1 signal and a received L2 signal, each having a single respective carrier modulated by a respective known code and by respective unknown codes wherein said unknown code causes adverse effects, said receiver comprising:
-
means for converting each said L1 and L2 signal to respective quadrature components; means for generating a respective model for each said carrier; means for generating a respective model for each said known code; means for counter-rotating said respective quadrature components of said L1 and L2 signal with said respective model carrier to produce respective counter-rotated signals; means for correlating said respective model code with said respective counter-rotated signals to produce at least one respective correlation product separately for each said respective counter-rotated signal; means for accumulating said respective correlation products successively over selected respective time intervals; means for combining with one another separately for the L1 and L2 signals said respective accumulated correlation products derived from said quadrature components of said L1 and L2 signals in a manner reducing said adverse effects of said unknown code; and
,means for generating an amplitude factor whereby said respective combined accumulated correlation products and amplitude factor are used to extract said signal'"'"'s amplitude, phase, and delay, in the presence of said unknown codes. - View Dependent Claims (20, 21, 22)
-
-
23. A method for processing a received signal transmitted as an L1 or an L2 signal comprised of a single carrier modulated by a known code and by an unknown code wherein said unknown code causes adverse effects, said method comprising the following steps:
-
converting said L1 or L2 signal to quadrature components; generating a model for said carrier; generating a model for said known code; counter-rotating said quadrature components of said L1 or L2 signal with said model carrier to produce counter-rotated signals; correlating said model code with said counter-rotated signals to produce at least one correlation product separately for each counter-rotated signal; accumulating said correlation products successively over selected time intervals; combining with one another said accumulated correlation products derived from said quadrature components of said L1 or L2 signal in a manner reducing said adverse effects of said unknown code; and
,generating an amplitude factor whereby said combined accumulated correlation products and amplitude factor are used to extract said signal'"'"'s amplitude, phase, and delay, in the presence of said unknown code.
-
Specification