Device and System for Suppression of Interference Linked to Distant Paths

• US 20120282873A1
• Filed: 12/02/2010
• Published: 11/08/2012
• Est. Priority Date: 12/04/2009
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Lucidarme, Thierry
• Granted Patent: US 8,660,552 B2
• Time in Patent Office: Days
• US Class Current: 455/297
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service

Abstract

An onboard device for receiving a signal coming from an aircraft at a distance d from the device, said signal resulting from the combination of multiple propagation paths, one of the paths corresponding to the main echo of the transmitted signal, said device including an equalizer of processing depth T. The device includes means for estimating the distance covered by the second path, means for deducing therefrom a delay value τ associated with it, means for estimating when τ is greater than or equal to T the interfering signal associated with the main echo and for reducing the contribution of said signal to the total level of interference received. Also a system of communication between aircraft using the onboard device.

Claims

1. An onboard device for receiving a signal s(t) coming from a transmitting aircraft at a distance d from the device, said signal s(t) resulting from the combination of a plurality of propagation paths, one of the paths corresponding to the main echo of the transmitted signal, said device comprising:

an equalizer of processing depth T;

means for estimating a distance D covered by the second path;

means for deducing therefrom a delay value τ

associated with the distance D; and

means for estimating when τ

is greater than or equal to T the interfering signal associated with the main echo and for reducing the contribution of said signal to the total level of interference received.

2. The device according to claim 1, wherein the distance D is estimated using the expression:

D=√

{square root over (d²+4×

ha×

hb)}

in which;

ha is the altitude of the device relative to sea level or ground level; and

hb is the altitude of the transmitting aircraft.

3. The device according to claim 1, further comprising means for subtracting from the received signal s(t) a version of said signal delayed by τ

in order to reduce the contribution of the main echo to the total length of interference received.

4. The device according to claim 3, further comprising means for estimating a differential Doppler shift Δ

f_diff using the following expression;

5. The device according to claim 4, wherein a coefficient β

is applied to the signal s′

(t−

τ

), said coefficient being such that it minimizes a mean square error between a received pilot signal and the received signal s(t).

6. The device according to claim 1, further comprising means for estimating a transfer function of the propagation channel in the area corresponding to the delay τ

of the main echo to reduce by equalization the contribution of the main echo to the total level of interference received.

7. The device according to claim 6, wherein said transfer function is obtained by processing pilot bits present in said area.

8. The device according to claim 6, further comprising conjoint pilot/data equalization means used to reduce the contribution of the main echo to the total level of interference received.

9. A satellite including the device according to claim 1.

10. An aircraft including the device according claim 1.

11. A system for communication between a plurality of aircraft comprising:

a first aircraft including at least one device for transmitting signals with a chosen waveform; and

the receiver device according to claim 1, said device enabling reception of signals using the chosen waveform.

12. The system according to claim 11, wherein the plurality of aircraft include an altitude measuring device.

13. The system according to claim 12, wherein the altitude measuring device is a radio altimeter.

14. The system according to claim 12, wherein the altitude measuring device is a GPS receiver.

15. The system according to claim 14, wherein the plurality of aircraft include means for reciprocal transmission of their position estimated by their GPS receiver.

16. The system according to claim 11, wherein the plurality of aircraft include means for reciprocal transmission of their altitude.