System and method for estimating terminal position based on non-geostationary communication satellite signals
View Patent ↗A device is provided for use with a satellite and a receiver having a local oscillator. The satellite is traveling in a vector and transmits a signal having an expected frequency. The receiver receives a received signal having a received signal frequency. The device includes: a Doppler shift measuring portion measuring a Doppler shift D m ; a predetermined Doppler shift storage portion storing a predetermined received Doppler shift D p ; a received signal Doppler shift error calculating portion calculating a received signal Doppler shift error D e ; a predetermined receiver position storage portion storing a predetermined position P p of the receiver; and a receiver position estimating portion calculating an estimated receiver position P e based on the predetermined position P p of the receiver and the received signal Doppler shift error D e .
1. A device comprising:
a receiver configured to receive ephemeris and time information regarding a communications satellite, and to receive a signal transmitted from the satellite, wherein the ephemeris information reflects velocity and direction data regarding the satellite;
a Doppler shift calculator configured to determine an expected Doppler shift D p and a measured Doppler shift D m based on the ephemeris information, a last known position of the device and the received signal;
a Doppler shift error calculator configured to determine a Doppler shift error D e based on the expected Doppler shift D p and the measured Doppler shift D m ; and
a position calculator configured to determine a predetermined position P p of the device based on the ephemeris information and the last known position of the device, and to determine an estimated change in distance P e of the device, along a maximum effect vector from the predetermined position P p , based on the predetermined position P p and the Doppler shift error D e .
2. The device according to claim 1 , wherein the Doppler shift error is determined as D e =D p −D m .
3. The device according to claim 2 , wherein the estimated change in distance of the device is determined as P e =P p +(K 2 ×D e ), wherein K 2 is a predetermined value associated with a position estimation loop.
4. The device according to claim 1 , further comprising:
a frequency calculator configured to determine a frequency correction factor f e , for correcting a local oscillator frequency, based on a predetermined oscillator frequency f p and the Doppler shift error D e .
5. The device according to claim 4 , wherein the Doppler shift error is determined as D e =D p −D m .
6. The device according to claim 5 , wherein the frequency correction factor is determined as f e =f p +(K 1 ×D e ), wherein K 1 is a predetermined value associated with a frequency estimation loop of the device.
7. The device according to claim 5 , wherein the estimated change in distance of the device is determined as P e =P p +(K 2 ×D e ), wherein K 2 is a predetermined value associated with a position estimation loop of the device.
8. The device according to claim 7 , wherein the frequency correction factor is determined as f e =f p +(K 1 ×D e ), wherein K 1 is a predetermined value associated with a frequency estimation loop of the device.
9. A method comprising:
receiving, by a satellite terminal (ST), ephemeris and time information regarding a communications satellite, and receiving a signal transmitted from the satellite, wherein the ephemeris information reflects velocity and direction data regarding the satellite;
determining an expected Doppler shift D p and a measured Doppler shift D m based on the ephemeris information, a last known position of the ST and the received signal;
determining a Doppler shift error D e based on the expected Doppler shift D p and the measured Doppler shift D m ; and
determining a predetermined position P p of the ST based on the ephemeris information and the last known position of the ST, and determining an estimated change in distance P e of the ST, along a maximum effect vector from the predetermined position P p , based on the predetermined position P p and the Doppler shift error D e .
10. The method according to claim 9 , wherein the Doppler shift error is determined as D e =D p −D m .
11. The method according to claim 10 , wherein the estimated change in distance of the ST is determined as P e =P p +(K 2 ×D e ), wherein K 2 is a predetermined value associated with a position estimation loop.
12. The method according to claim 9 , further comprising:
a frequency calculator configured to determine a frequency correction factor f e , for correcting a local oscillator frequency, based on a predetermined oscillator frequency f p and the Doppler shift error D e .
13. The method according to claim 12 , wherein the Doppler shift error is determined as D e =D p −D m .
14. The method according to claim 12 , wherein the frequency correction factor is determined as f e =f p +(K 1 ×D e ), wherein K 1 is a predetermined value associated with a frequency estimation loop of the ST.
15. The method according to claim 13 , wherein the estimated change in distance of the ST is determined as P e =P p +(K 2 ×D e ), wherein K 2 is a predetermined value associated with a position estimation loop of the ST.
16. The method according to claim 15 , wherein the frequency correction factor is determined as f e =f p +(K 1 ×D e ), wherein K 1 is a predetermined value associated with a frequency estimation loop of the ST.