METHOD AND DEVICE FOR COMPRESSING A WIDE BAND RADIO-NAVIGATION SIGNAL, ASSOCIATED METHOD AND DEVICE FOR CALCULATING THE CORRELATION FUNCTION OF THE SPREADING CODE OF THE SAID COMPRESSED SIGNAL

• US 20140348210A1
• Filed: 03/13/2014
• Published: 11/27/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Revol, Marc
• Granted Patent: US 9,094,109 B2
• Time in Patent Office: Days
• US Class Current: 375/142
• CPC Class Codes: G01S 19/09 providing processing capability normally carried out by the receiver
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: H04B 1/7073 Synchronisation aspects
• CPC Class Codes: H04B 1/709 Correlator structure

Abstract

The invention relates to a method for compressing a wide band satellite radio-navigation signal in order to transmit it on a narrow band channel and to a method for calculating the correlation function of the spreading code of a satellite radio-navigation signal compressed by application of the compression method.

Claims

1. Method for compressing a wide band satellite radio-navigation signal in order to transmit it on a narrow band channel, said method comprising the following steps:

a step of receiving a satellite radio-navigation signal,

a step of spectral conversion of the said signal into a plurality N of frequency channels of reduced bandwidth,

a step of time-shifting each of the channelled signals by a predetermined distinct delay, the delay being configured so as to be greater than the duration of the correlation support of the spreading code of a channelled signal,

a step of accumulation of the shifted channelled signals in order to produce a compressed signal.

2. to the method of claim 1, wherein the spectral conversion step is carried out by means of a fast Fourier transform.

3. The method of claim 1, wherein the predetermined delay is equal to a multiple, different for each of the channelled signals, of a predetermined delay Δ

T of duration greater than the duration of the correlation support of the spreading code of a channelled signal.

4. to the method of claim 3, wherein the duration of the correlation support of the spreading code of a channelled signal is equal to the inverse of the width of a frequency channel.

5. The method of claim 1, wherein the plurality N of frequency channels covers the whole of the wide band of the radio-navigation signal.

6. The method of claim 1, furthermore comprising a step of selection of a sub-set of M channels from among the plurality N of frequency channels, the said steps of time shifting and of accumulation being carried out solely for the M channelled signals of the said sub-set.

7. The method of claim 6, wherein the selection of the said sub-set of M channels is carried out periodically by a random selection from among the N available channels.

8. Method for calculating the correlation function of the spreading code of a satellite radio-navigation signal compressed by application of the compression method according to claim 1, said method comprising the following steps:

a step of receiving a compressed signal transmitted on a narrow band,

a step of spectral conversion of a locally generated spreading code into a plurality N of frequency channels,

a step of time shifting the said received compressed signal by a plurality of predetermined distinct delays in order to obtain a plurality of delayed signals, the said delays being configured so as to be greater than the duration of the correlation support of the channelled spreading code, the number of delayed signals being equal to the number N of frequency channels,

a step of calculation of the complex conjugate pair product between a delayed signal and a channel of the spectrum of the said locally generated spreading code in order to obtain an intermediate signal,

a step of calculation of the inverse Fourier transform of the said intermediate signal in order to obtain the correlation function of the spreading code of the said radio-navigation signal.

9. The method of claim 8, wherein the spectral conversion step is carried out by means of a fast Fourier transform.

10. The method of claim 8, wherein the said predetermined delays are equal to a multiple, different for each delay, of a predetermined delay Δ

T of duration greater than the duration of the correlation support of the channelled spreading code.

13. Device for calculating the correlation function of the spreading code of a satellite radio-navigation signal compressed by application of the compression method according to claim 1, said device comprising:

means of spectral conversion of a locally generated spreading code into a plurality N of frequency channels,

means of time shifting the said radio-navigation signal by a plurality of predetermined distinct delays in order to obtain a plurality of delayed signals, the said delays being configured so as to be greater than the duration of the correlation support of the channelled spreading code,

means for calculating the complex conjugate pair product between a delayed signal and a channel of the spectrum of the said locally generated spreading code in order to obtain an intermediate signal,

means for calculating the inverse Fourier transform of the said intermediate signal in order to obtain the correlation function of the spreading code of the said radio-navigation signal.

14. Receiving station comprising means for receiving a compressed radio-navigation signal on a narrow band and a device, according to claim 13, for calculating the correlation function of the spreading code of the said received compressed radio-navigation signal.

11. Device for compressing a wide band satellite radio-navigation signal in order to transmit it on a narrow band channel, comprising:

means for spectrally converting the said signal into a plurality N of frequency channels of reduced bandwidth,

means for time shifting each of the channelled signals by a predetermined distinct delay, the delay being configured so as to be greater than the duration of the correlation support of a channelled signal,

means for accumulating the said shifted channelled signals in order to produce a compressed signal.

12. Transmitting terminal comprising means for receiving a satellite radio-navigation signal, a device for compressing the said satellite radio-navigation signal according to claim 11 and means for transmitting the said compressed signal on a narrow band channel.