US5068872A
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Apparatus and method for short cycling sequences of a p-code generator
Assignee: Raytheon Co
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Filing: 1989-11-27
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Granted: 1991-11-26
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Expires: 2009-11-27
Abstract
Abstract An improved short cycled sequencer of a P-code generator is disclosed for generating a ranging code in a Global Positioning System receiver. A shift register in the sequencer has a predetermined number of stage outputs exclusive-ored with a decoded outpout of the shift register stages and the exclusive-ored output is fed back to the serial input of the shift register. At the end of sequencing through a plurality of vectors, reinitialization of the shift register occurs without having to load an initialization vector from an external source.
Inventors
- 👤 John C. Schroter
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 20:05
CPC Classifications
H; H03; H03K; H03K3/00; H03K3/84; G; G01; G01S; G01S11/00; G01S11/02; G01S11/08; G01S19/00; G01S19/01; G01S19/13; G01S19/24; G01S19/30
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
143 words
A P-code generator of a Global Positioning System comprising: a plurality of pseudo-random number generators for generating a ranging P-code, each of said generators having a sequencer means for determining said ranging P-code; shift register means included in each of said sequencer means comprising a plurality of stages, said shift register means having a serial input port, a serial output port, and shifting in accordance with an input signal; decoder means coupled to each stage of said shift register means for generating a decode signal when the contents of said shift register means equals one predetermined vector word; and means coupled to an output port of said decoder means and to a plurality of predetermined stages of said shift register means for generating a feedback signal fed to said serial input port of said shift register means to short cycle said sequencer means.
Claim 2
Dependent Claim
143 words
A P-code generator of a Global Positioning System comprising: a plurality of pseudo-random number generators for generating a ranging P-code, each of said generators having a sequencer means for determining said ranging P-code; shift register means included in each of said sequencer means comprising a plurality of stages, said shift register means having a serial input port, a serial output port, and shifting in accordance with an input signal; decoder means coupled to each stage of said shift register means for generating a decode signal when the contents of said shift register means equals one predetermined vector word; and means coupled to an output port of said decoder means and to a plurality of predetermined stages of said shift register means for generating a feedback signal fed to said serial input port of said shift register means to short cycle said sequencer means.
Claim 3
Dependent Claim
30 words
The P-code generator as recited in claim 1 wherein: each of said pseudo-random number generators comprises a register means for loading an initial vector word into said shift register means.
Claim 4
Dependent Claim
18 words
The P-code generator as recited in claim 1 wherein: said feedback signal generating means comprises an exclusive-OR gate.
Claim 5
Dependent Claim
98 words
The P-code generator as recited in claim 1 wherein said generator further comprises: means for generating an X1 signal by performing a modulo-2 sum on an output signal of a first one and an output signal of a second one of said plurality of generators; means for generating an X2 signal by performing a modulo-2 sum on an output signal of a third one and an output signal of a fourth one of said plurality of generators; and means for generating said P-code by performing a modulo-2 sum on said generated X1 signal and said generated X2 signal.
Claim 6
Independent Claim
157 words
A method of generating a ranging P-code of a Global Positioning System comprising the steps of: generating sequences of pseudo-random numbers with a plurality of pseudo-random number generators, each of said generators having a sequencer means for determining said P-code; providing a shift register means in each of said sequencer means for shifting a vector word in accordance with an input signal, said shift register means having a plurality of stages, a serial input port and a serial output port; generating a decode signal with a decoder means coupled to each stage of said shift register means when the contents of said shift register equals one predetermined vector word; generating a feedback signal based on said decode signal and output signals of predetermined stages of said plurality of stages of said shift register means; and feeding said feedback signal to said serial input port of said shift register means to perform short cycling of said sequencer means.
Claim 7
Independent Claim
157 words
A method of generating a ranging P-code of a Global Positioning System comprising the steps of: generating sequences of pseudo-random numbers with a plurality of pseudo-random number generators, each of said generators having a sequencer means for determining said P-code; providing a shift register means in each of said sequencer means for shifting a vector word in accordance with an input signal, said shift register means having a plurality of stages, a serial input port and a serial output port; generating a decode signal with a decoder means coupled to each stage of said shift register means when the contents of said shift register equals one predetermined vector word; generating a feedback signal based on said decode signal and output signals of predetermined stages of said plurality of stages of said shift register means; and feeding said feedback signal to said serial input port of said shift register means to perform short cycling of said sequencer means.
Claim 8
Dependent Claim
31 words
The method as recited in claim 5 comprises the step of: loading a predetermined initial vector word into said shift register means of each of said plurality of pseudo-random number generators.
Claim 9
Dependent Claim
39 words
The method as recited in claim 5 wherein: said step of generating said feedback signal comprises coupling said decode signal and said output signals of predetermined stages of said plurality of stages to input terminals of an exclusive-OR gate.
Claim 10
Dependent Claim
147 words
A P-code generator of a Global Positioning System comprising: a plurality of pseudo-random number generators for generating a ranging P-code; sequencer means in each of said pseudo-random number generators for sequencing to a predetermined vector word from a preset initial vector word prior to being short cycled to said initial vector word in accordance with a feedback signal; means for generating an X1 signal by performing a modulo-2 sum on an output signal of a first one and an output signal of a second one of said plurality of pseudo-random number generators; means for generating an X2 signal by performing a modulo-2 sum on an output signal of a third one and an output signal of a fourth one of said plurality of pseudo-random number generators; and means for generating said P-code by performing a modulo-2 sum on said generated X1 signal and said generated X2 signal.
Claim 11
Dependent Claim
147 words
A P-code generator of a Global Positioning System comprising: a plurality of pseudo-random number generators for generating a ranging P-code; sequencer means in each of said pseudo-random number generators for sequencing to a predetermined vector word from a preset initial vector word prior to being short cycled to said initial vector word in accordance with a feedback signal; means for generating an X1 signal by performing a modulo-2 sum on an output signal of a first one and an output signal of a second one of said plurality of pseudo-random number generators; means for generating an X2 signal by performing a modulo-2 sum on an output signal of a third one and an output signal of a fourth one of said plurality of pseudo-random number generators; and means for generating said P-code by performing a modulo-2 sum on said generated X1 signal and said generated X2 signal.
Claim 12
Dependent Claim
25 words
The P-code generator as recited in claim 8 wherein: each of said sequencer means comprises a shift register means preloaded with said initial vector word.
Claim 13
Dependent Claim
44 words
The P-code generator as recited in claim 9 wherein: said sequencer means comprises logic means coupled to predetermined stages of said shift register means and a decode signal for generating said feedback signal being fed to a serial input port of said shift register.
Claim 14
Independent Claim
152 words
A method of generating a ranging P-code of a Global Positioning System comprising the steps of: generating said ranging P-code with a plurality of pseudo-random number generators, each of said generators having a sequencer means; sequencing to a predetermined vector word from a preset initial vector word in said sequencer means prior to being short cycled to said initial vector word in accordance with a feedback signal; generating an X1 signal by performing a modulo-2 sum on an output signal of a first one and an output signal of a second one of said plurality of pseudo-random number generators; generating an X2 signal by performing a modulo-2 sum on an output signal of a third one and an output signal of a fourth one of said plurality of pseudo-random number generators; and means for generating said P-code by performing a modulo-2 sum on said generated X1 signal and said generated X2 signal.
Claim 15
Independent Claim
152 words
A method of generating a ranging P-code of a Global Positioning System comprising the steps of: generating said ranging P-code with a plurality of pseudo-random number generators, each of said generators having a sequencer means; sequencing to a predetermined vector word from a preset initial vector word in said sequencer means prior to being short cycled to said initial vector word in accordance with a feedback signal; generating an X1 signal by performing a modulo-2 sum on an output signal of a first one and an output signal of a second one of said plurality of pseudo-random number generators; generating an X2 signal by performing a modulo-2 sum on an output signal of a third one and an output signal of a fourth one of said plurality of pseudo-random number generators; and means for generating said P-code by performing a modulo-2 sum on said generated X1 signal and said generated X2 signal.
Claim 16
Dependent Claim
31 words
The method as recited in claim 11 wherein: said step of sequencing further comprises the step of loading said preset initial vector word into a shift register of said sequencer means.
Claim 17
Dependent Claim
44 words
The method as recited in claim 12 wherein: said sequencing step further comprises the step of coupling predetermined stages of said shift register and a decode signal to logic means for generating said feedback signal fed to a serial input of said shift register.
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