Enhanced global positioning system Delta-Range processing

• US 4,646,096 A
• Filed: 10/05/1984
• Issued: 02/24/1987
• Est. Priority Date: 10/05/1984
• Status: Expired due to Term

• Current Assignee: Litton Systems Incorporated
• Original Assignee: Litton Systems Incorporated
• Inventors: Brown, Alison
• Primary Examiner(s): Blum, Theodore M.
• Assistant Examiner(s): GREGORY, BERNARR E
• Application Number:
  US06/659,231
• Time in Patent Office: 872 Days
• Field of Search: 343/6.5 R, 343/6.5 LC, 343/7 PL, 343/352, 343/356-358, 343/394, 364/443, 364/449, 364/457, 370/104, 375/97
• US Class Current: 342/357.25
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

A circuit is shown which utilizes signals transmitted from global positioning system satellites to create change in phase signals. The change in phase signals are measured over a predetermined time interval, one second, and stored. The stored signals are applied to a Kalman filter and back to the storage unit so that each one second time interval includes the information from all previous time intervals. This accumulated information is referred to as accumulated Delta-Range information which permits a more rapid determination of position by the circuit.

Claims

1. A method for enhancing the information received from a global positioning system which includes a plurality of satellites each transmitting at least two carrier frequency signals, comprising the steps of:

(a) identifying a plurality of selected satellites;

(b) setting information storage units for accumulated Delta-Range information for each selected satellite to zero;

(c) tracking the selected satellites;

(d) receiving said carrier frequency signals from said selected satellites;

(e) measuring the phase of said carrier frequency signals from said selected satellites;

(f) storing changes in phase of said carrier frequency signals over a predetermined time interval in said storage units to create a Delta-Range measurement for each selected satellite;

(g) accumulating the Delta-Range measurement by adding the above-mentioned accumulated Delta-Range information for each satellite to the Delta-Range measurement from step f for each satellite;

(h) processing the accumulated Delta-Range information from each selected satellite through a filter which receives said input information and produces said information into output information, said output information being position information; and

(i) repeating steps f, g and h until said position information is refined to the accuracy desired.

2. A method, as claimed in claim 1, wherein:

step a includes the selection of four satellites.

3. A method, as claimed in claim 1, wherein:

step f includes a one second time interval.

4. A method, as claimed in claim 1, wherein:

step h includes the use of a Kalman filter.

8. Apparatus, as claimed in claim 1, wherein:

said filter means includes a Kalman filter.

5. Apparatus for enhancing the information received from a global positioning system which includes a plurality of satellites each transmitting at least two carrier frequency signals, comprising:

(a) means for selecting a plurality of satellites whose transmitted signals are to be received;

(b) means for storing;

(c) means for setting each means for storing to zero;

(d) means for receiving said carrier frequency signals from said selected satellites;

(e) means for measuring the phase of said carrier frequency signals received from said selected satellites;

(f) means for measuring changes in phase of said carrier frequency signals over a predetermined time interval;

(g) means for placing said measured changes in phase in said means for storing over said time interval to create a Delta-Range measurement for each selected satellite;

(h) means for accumulating said Delta-Range measurement by adding the above mentioned accumulated Delta-Range information for each satellite to said Delta-Range measurement;

(i) filter means for processing said accumulated Delta-Range information for each selected satellite for producing an output representing position information.

6. Apparatus, as claimed in claim 5, wherein:

said plurality of satellites includes four satellites.

7. Apparatus, as claimed in claim 5, wherein:

said time interval includes a one second time interval.

9. An apparatus for improving the accuracy of measurement information obtained from a plurality of satellites of a global positioning system, said apparatus comprising:

a satellite selectable global positioning system receiver, said receiver being capable of receiving at least two carrier frequencies from each selected satellite and tracking the difference between their phase measurements, to produce Delta-Range signals which are derived from said phase measurements;

said global positioning system receiver being operatively associated with a resettable data storage and accumulation means, said receiver providing said data storage and accumulation means with said Delta-Range signals;

said resettable data storage and accumulation means storing and accumulating said Delta-Range signals over a first time interval;

said resettable storage means processing said Delta-Range signals to develop a first set of Accumulated Delta-Range signals, said first set of signals being a function of the accumulation of Delta-Range signals at said storage means during said first time interval;

said storage means operatively connected to a filter means, said storage means transmitting said Accumulated Delta-Range signals to said filter and simultaneously feeding back said signals to the storage means, so that said Accumulated Delta-Range signals may be stored in said storage means during a second time interval and processed together with a second set of Delta-Range signals, for deriving a second set of Accumulated Delta-Range signals at the end of said second time interval, at which time said second set of Accumulated Delta-Range signals are transmitted to said filter means;

said filter means further processing said first and said second sets of Accumulated Delta-Range signals from each selected satellite to develop an output signal representative of enhanced position information.

10. The apparatus of claim 9 wherein the Accumulated Delta-Range signals are continuously processed and updated by said storage means over a subsequent series of time intervals, said filter means processing a subsequently derived series of Accumulated Delta-Range signals, thereby the position information so derived is continually updated and made more accurate at the end of each of said subsequent time intervals.

11. The apparatus of claim 9 wherein the filter is a Kalman Filter.

12. A method for improving the accuracy of position measurement information obtained from a global positioning system having a plurality of satellites, each of said satellites transmitting at least two carrier frequency signals, comprising the steps of:

(a) receiving the transmitted satellite carrier frequency signals;

(b) processing said satellite signal through a receiver means capable of identifying and tracking each of the satellites according to their transmitted carrier frequency signals;

(c) deriving an output signal from said receiver means which is characteristic of Delta-Range information for each of said satellites;

(d) processing said output signal through a data accumulation and storage means, deriving an Accumulated Delta-Range information signal, by storing said signal for a predetermined time interval, creating an Accumulated Delta-Range information signal corresponding to each satellite;

(e) repeating said step (d) to further refine the signal so processed, whereby an Accumulated Delta-Range signal is derived which corresponds to an accurate position for each satellite to the degree desired.

13. The method of clam 12, wherein the Accumulated Delta-Range signal derived as a result of steps (d) and (e) is further repeatedly processed through a Kalman Filter to correlate said accumulated signals and correct the information derived, so information obtained from signal processing is further refined and more accurately presented.