Autonomous satellite navigation system

• US 6,608,589 B1
• Filed: 04/21/1999
• Issued: 08/19/2003
• Est. Priority Date: 04/21/1999
• Status: Expired due to Term

• Current Assignee: Johns Hopkins University
• Original Assignee: Johns Hopkins University
• Inventors: Chacos, Albert A., Morgan, Richard C., Devereux, William S., Strohbehn, Kim, Gruenbacher, Don M., Heins, Robert J., Asher, Mark S., Kusterer, Thomas L., Linstrom, Lloyd A., Duven, Dennis J.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/295,544
• Time in Patent Office: 1,581 Days
• Field of Search: 342/357.06, 342/357.12, 342/357.15, 701/213, 701/226, 701/13, 375/149, 375/150
• US Class Current: 342/357.29
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/54 using carrier phase measurements; using long or short baseline interferometry

Abstract

An autonomous navigation system for an orbital platform incorporating a global positioning system based navigation device optimized for low-Earth orbit and medium-Earth orbit applications including a 12-channel, GPS tracking application-specific integrated circuit operating in concert with a microprocessor implementing an extended Kalman filter and orbit propagator which autonomously generates estimates of position, velocity, and time to enable planing, prediction and execution of event-based commanding of mission operations.

Claims

1. A satellite navigation system, comprising:

a radio frequency receiver incorporating a plurality of channels for concurrently processing code containing signals received from a plurality of global positioning system satellites, wherein said radio frequency receiver comprises;

a plurality of antennas;

a plurality of preamplifiers, driven by each one of said plurality of antennas; and

a separate downconverter for each one of said preamplifiers for processing the amplified signals produced thereby, wherein each of said downconverters comprises;

a phase locked loop frequency synthesizer;

a reference oscillator for driving said phase locked loop frequency synthesizer;

a mixing means for combining an output of said phase locked loop frequency synthesizer with an output of said preamplifier;

an intermediate frequency band pass filter for processing the output of said mixing means; and

a quantizer for producing a pair of complementary signals from an output of said intermediate frequency band pass filter;

a microprocessor for executing software which manipulates data processed by said plurality of channels according to an extended Kalman filter to autonomously generate estimates of position, velocity, time and earth-sun vector data;

position-based event notifications and predictions; and

orbit determinations; and

an application specific integrated circuit for tracking said code containing GPS signals, wherein said application specific integrated circuit comprises;

a latch circuit for sampling said pair of complementary signals from two of said downconverters and producing therefrom a pair of complementary quadrature signal samples and a pair of complementary non-quadrature signal samples;

a plurality of tracker channels, wherein said tracker channels each comprises;

a plurality of accumulators;

a separate latch register for outputting the contents of each of said accumulators for outputting the contents thereof;

a coarse acquisition code generator; and

a differential mixer for combining said signal samples with a code created by said course acquisition code generator to lock the phase and frequency of said code carried by said signal samples with said code created by said course acquisition code generator; and

a data router for distributing each of said complimentary signal sample pairs to a different one of said tracker channels;

wherein the application specific integrated circuit produces tracking data for each of said global positioning system satellites from said amplified signals processed by said downconverters;

wherein the radio frequency receiver, the microprocessor, and the application specific integrated circuit are onboard the satellite.

2. A satellite navigation system, comprising:

a radio frequency receiver incorporating a plurality of channels for concurrently processing code containing signals received from a plurality of global positioning system satellites;

a microprocessor for executing software which manipulates data processed by said plurality of channels according to an extended Kalman filter to autonomously generate estimates of position, velocity, time and earth-sun vector data;

position-based event notifications and predictions; and

orbit determinations;

an application specific integrated circuit for tracking said code containing GPS signals;

a plurality of input channels for producing GPS signal samples, wherein each of said input channels comprises;

a first exclusive NOR gate for processing a pair of complementary non-quadrature signals derived from one of said code containing signals;

a second exclusive NOR gate for processing a pair of complementary quadrature signals derived from one of said code containing signals;

a first multiplexer for producing a non-quadrature signal sample in response to an input from said first exclusive NOR gate;

a second multiplexer for producing a first quadrature signal sample in response to an input from said second exclusive NOR gate;

a third multiplexer for producing a second quadrature signal sample complementary to said first quadrature signal sample from one of said complementary non-quadrature signals and one of said complementary quadrature signals; and

an output means for a non-quadrature signal sample complementary to said signal sample produced by said first multiplexer from said one of said complementary non-quadrature signals;

a plurality of tracker channels for accumulating code carried by said GPS signal samples, wherein each of said tracker channels comprises;

a numerically control oscillator;

means for combining a cosine function of said numerically control oscillator with said non-quadrature signal samples received from said IF input channel;

means for combining a cosine function of said numerically control oscillator with said quadrature signal samples received from said IF input channel;

means for combining a sine function of said numerically control oscillator with said non-quadrature signal samples received from said IF input channel;

means for combining a sine function of said numerically control oscillator with said quadrature signal samples received from said IF input channel;

means for summing a product of said cosine function combined non-quadrature signal samples and said sine function combined quadrature signal samples;

means for summing a product of said cosine function combined quadrature signal samples and said sine function combined non-quadrature signal samples;

a non-quadrature flip-flop for producing a plurality of parallel output signals of different values from an output of said means for summing a product of said cosine function combined non-quadrature signal samples and said sine function combined quadrature signal samples;

a quadrature flip-flop for producing a plurality of parallel outputs signals of different values from an output of said means for summing a product of said cosine function combined quadrature signal samples and said sine function combined non-quadrature signal samples;

a coarse acquisition coated generator;

a coarse acquisition code numerically control oscillator for controlling said coarse acquisition code generator;

a multibit shift register responsive to outputs from said coarse acquisition code numerically control oscillator and said coarse acquisition code generator for producing a plurality of time shifted coarse acquisition codes for combining with said plurality of outputs from said non-quadrature and quadrature differentiators;

a plurality of accumulators, each of which accumulates code resulted from said combination of said time shifted coarse acquisition codes and said plurality of outputs from said non-quadrature and quadrature flip-flop; and

a latch register for each of said accumulators for setting and output thereof;

a data router for distributing said GPS signal samples to said tracker channels as a function of tracker channel availability and said global positioning system satellite originating said GPS signal samples;

a timing means synchronizing the circuits of said application-specific integrated circuit; and

a bus interface for coupling said accumulated code to said microprocessor and for receiving controlling data from said microprocessor;

wherein the radio frequency receiver, the microprocessor, and the application specific integrated circuit are onboard the satellite.

3. The satellite navigation system as defined by claim 2, wherein the sampling times of the tracker channels are controlled to align with Universal Coordinated Time (UTC) time tics.