Satellite and local system position determination
View Patent ↗In a local positioning system, augmentation of the land-based system is provided by receiving signals from a GNSS. The signals from the land-based positioning system have a code phase accuracy better than one wavelength of a carrier of the signals from the GNSS. Different decorrelation may be used for signals from a satellite than from a land-based transmitter, such as using a digital decorrelator for signals from the satellite and an analog decorrelator for signals from a land-based transmitter. The receivers may include both a GNSS antenna and a local antenna. The phase centers of the two antennas are within one wavelength of the GNSS signals from each other. The local antenna is sized for operation in the X or ISM-bands of frequencies. The GNSS antenna is a patch antenna where the microwave antenna extends away from the patch antenna in at least one dimension.
1. A system for determining a position of a receiver from transmitted signals, the system comprising:
a digital de-correlator operable to de-correlate first signals from at least one satellite;
an analog de-correlator operable to de-correlate second signals from at least one land based transmitter; and
a processor operable to determine the position of the receiver as a function of the outputs of the digital and analog decorrelators;
wherein the second signals have a modulation rate of a second code being at least 30 MHz carried in the X-band, JSM band or combinations thereof.
2. The system of claim 1 wherein the second signals from the at least one land based transmitter have a code phase range accuracy better than one wavelength of a carrier of the first signals from the at least one satellite.
3. The system of claim 1 further comprising:
first and second analog-to-digital converters;
wherein the digital de-correlator comprises:
a first code generator; and
a digital mixer operable to mix a first code output by the first code generator with the first signals output by the first analog-to-digital converter;
wherein the analog de-correlator comprises:
a second code generator; and
an analog mixer operable to mix a second code output by the second code generator with the second signals;
wherein the second analog-to-digital converter is operable to convert the mixed second code and second signals from analog to digital.
4. The system of claim 1 wherein the first signals have a carrier with a wavelength greater than 15 cm, and measurements of the second signals have code phase range accuracy better than 2 cm.
5. The system of claim 1 wherein the modulation rate of the second code of the second signals is at least ten times a first code modulation rate of the first signals.
6. The system of claim 1 wherein the first and second signals are direct-sequence, spread spectrum signals responsive to a first code and the second code, respectively, the first code different than the second code.
7. The system of claim 1 wherein the first signals have a carrier with a wavelength greater than 15 cm, and measurements of the second signals have accuracy better than one-half wavelength of the carrier of the first signals.
8. A method for determining a position of a receiver from transmitted signals, the method comprising:
(a) digital de-correlating first signals from at least one satellite;
(b) analog de-correlating second signals from at least one land based transmitter; and
(c) determining the position of the receiver as a function of the de-correlated first and second signals;
wherein (a) comprises de-correlating the first signals, the first signals having a carrier with a wavelength greater than 15 cm; and
wherein (b) comprises de-correlating the second signals, the second signals having a better than 2 cm code phase range accuracy.
9. The method of claim 8 wherein (b) comprises de-correlating the second signals from the at least one land based transmitter, the code phase range accuracy better than one wavelength of a carrier of the first signals from the at least one satellite.
10. The method of claim 8 wherein (a) comprises mixing a first code with the first signals after converting the first signals from analog to digital; and
wherein (b) comprises mixing a second code with the second signals prior to converting the mixed second code and signals from analog to digital.
11. The method of claim 8 wherein (b) comprises de-correlating the second signals, the second signals having a modulation rate of a code being at least 30 MHz carried in the X-band, ISM band or combinations thereof.
12. The method of claim 8 wherein (b) comprises de-correlating the second signals, the second signals have a second code modulation rate at least ten times a first code modulation rate of the first signals.
13. The method of claim 8 wherein (a) and (b) comprise de-correlating direct-sequence, spread spectrum signals responsive to different codes.
14. The method of claim 8 wherein the code phase range has an accuracy better than one-half wavelength of the carrier of the first signals.
15. A system for determining a position of a receiver from transmitted signals, the system comprising:
a digital de-correlator operable to de-correlate first signals from at least one satellite;
an analog de-correlator operable to de-correlate second signals from at least one land based transmitter; and
a processor operable to determine the position of the receiver as a function of the outputs of the digital and analog decorrelators;
wherein the first signals have a carrier with a wavelength greater than 15 cm, and measurements of the second signals have code phase range accuracy better than 2 cm.