Method for treating signal in the presence of interference

• US 20050169409A1
• Filed: 03/07/2003
• Published: 08/04/2005
• Est. Priority Date: 03/22/2002
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Coatantiec, Blandine, Issler, Jean-Luc, Martin, Nicolas, Revol, Marc
• Granted Patent: US 7,295,635 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/71 the interference being narrowband interference
• CPC Class Codes: H04B 1/7101 with estimation filters
• CPC Class Codes: H04B 2201/70707 Efficiency-related aspects
• CPC Class Codes: H04B 7/216 Code division or spread-spectrum multiple access [CDMA, SSMA]

Abstract

The invention relates to methods of processing signals subjected to interference. It consists, when this signal is formed of a first wideband channel and of a second narrowband channel modulating one and the same carrier in which these signals are cut off for the duration of the interference, in using a single phase loop and a single code loop to process these two channels simultaneously. It makes it easier to process signals in satellite based navigation systems of the GPS type when they are scrambled by the DME-type distance measuring system signals, as well as more generally making it possible to increase the robustness of the processing by joint processing of the bands broadcast to the users.

Claims

1. A method of signal processing in the presence of interference, this signal including a first wideband channel (WB) and a second narrowband channel (NB) modulating one and the same carrier (FO), comprising the step of simultaneously processing said two channels using a single phase loop and a single code loop.

2. The method as claimed in claim 1, wherein a phase loop signal is generated at the frequency of the carrier, the phase loop signal is sine and cosine phase-shifted and the first channel and the second channel are demodulated synchronously with these two phase-shifted signals so as to obtain a signal I_WB and a signal Q_WB and a signal I_NB and a signal Q_NB respectively.

3. The method as claimed in claim 2, wherein the code loop a signal is generated at the frequency of the code of the wideband signal, a first punctual code and a first Δ

code are generated on the basis of this signal, the first Δ

code is multiplied respectively with the signal I_NB and the signal Q_NB, the first punctual code is multiplied with the signal I_NB and the signal Q_NB, the signals resulting from these multiplications are integrated to obtain signals I_PNB, I<sub>Δ

NB</sub>, Q_PNB and Q<sub>Δ

NB</sub>, a second Δ

signal and a second punctual signal are generated on the basis of the code frequency signal, the second Δ

signal is multiplied respectively with the signal I_WB and the signal Q_WB, the second punctual signal is multiplied by the signal I_WB and the signal Q_WB, and the signals resulting from these multiplications are integrated to obtain signals I_PWB, I<sub>Δ

WB</sub>, Q_PWB and Q<sub>Δ

WB</sub>.

4. The method as claimed in claim 3, wherein the signals I_PWB, I_Δ

WB, Q_PNB and Q<sub>Δ

NB</sub> are used in a first phase discriminator common to the two signals, wideband and narrowband, to obtain the phase of the carrier and to drive, after filtering, the oscillator making it possible to obtain said signal at the frequency of the carrier.

5. The method as claimed in claim 4, wherein in the first phase discriminator the input signals are mixed before the discrimination proper according to proportions determined by the formulae:

I_popt=α

I_pWB+β

_IpNB
Q_popt=α

Q_pWB+β

Q_pNB

6. The method as claimed in claim 5, wherein the parameters α

and β

are determined by the formulae;

7. The method as claimed in claim 5, wherein the signals I_PWB, I_Δ

WB, Q_PWB, Q<sub>Δ

WB</sub>, I_PNB, I<sub>Δ

NB</sub>, Q_PNB and Q<sub>Δ

NB</sub> are used in a second phase discriminator common to the two channels, wideband and narrowband, to obtain the setting of the two codes and to drive, after filtering, the oscillator making it possible to obtain said signal at the code frequency.

8. The method as claimed in claim 7, wherein the second phase discriminator the input signals are mixed before the discrimination proper according to proportions determined by the formulae:

I<sub>Δ

opt</sub>=(al<sub>Δ

WB</sub>+bl<sub>Δ

NB</sub>)
Q<sub>Δ

opt</sub>=(aQ<sub>Δ

WB</sub>+bQ<sub>Δ

NB</sub>)

9. The method as claimed in claim 8, wherein the parameters a and be are determined by the formulae:

10. The method as claimed in claim 6, wherein the signals I_PWB, I_Δ

WB, Q_PWB, Q<sub>Δ

WB</sub>, I_PNB, I<sub>Δ

NB</sub>, Q_PNB and Q<sub>Δ

NB</sub> are used in a second phase discriminator common to the two channels, wideband and narrowband, to obtain the setting of the two codes and to drive, after filtering, the oscillator making it possible to obtain said signal at the code frequency.