Method and device for notching the transmission band of an analog signal, in particular for a detect and avoid (DAA) operation mode of an MB-OFDM system

1. A method of notching a transmission band of a signal including successive symbols to be transmitted, with each symbol comprising sub-carriers to be modulated, the method comprising:

suppressing in at least some of the symbols the sub-carriers corresponding to a part of the transmission band to be notched;

suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated; and

multiplying in a time-domain the symbols by a windowing mask configured to keep orthogonality between the sub-carriers to be transmitted and to decrease side-lobe power of the sub-carriers to be transmitted, with the windowing mask being based on a rectangular mask multiplied by an auxiliary function.

2. The method according to claim 1 , wherein suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises keeping in at least some of the symbols one remaining sub-carrier every n remaining sub-carriers, with n being an integer smaller than five and suppressing all other remaining sub-carriers of each symbol.

3. The method according to claim 1 , wherein suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises suppressing half of the remaining sub-carriers in each symbol.

4. The method according to claim 3 , wherein suppressing in at least some of the symbols half of the remaining sub-carriers comprises suppressing every other remaining sub-carrier.

5. The method according to claim 4 , wherein suppressing in at least some of the symbols every other remaining sub-carrier comprises suppressing alternately even and odd remaining sub-carriers respectively in two successive symbols.

6. The method according to claim 1 , wherein the auxiliary function is based on a Gaussian function.

7. The method according to claim 1 , wherein suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises keeping in each symbol one remaining sub-carrier every n remaining sub-carriers, with n being an integer smaller than five and suppressing all other remaining sub-carriers of the symbol; and

wherein elaborating the windowing mask comprises:

providing a time-domain rectangle mask having a length equal to one nth of a length of a symbol;

zero-padding the time domain rectangle mask to reach an initial time domain mask having a length equal to the length of a symbol;

performing a time-domain to frequency-domain conversion processing of an initial time domain mask for obtaining a frequency-domain resulting mask;

multiplying the resulting mask with the auxiliary function for obtaining a modified mask; and

performing a frequency-domain to time-domain conversion processing on the modified mask for obtaining the windowing mask.

8. The method according to claim 1 , wherein the signal comprises an Ultra Wide Band (UWB) signal modulated according to a multiband Orthogonal Frequency-Division Multiplexing (MB-OFDM) modulation scheme.

9. A device for notching a transmission band of a signal including successive symbols to be transmitted, with each symbol comprising sub-carriers to be modulated, the device comprising:

a processor configured to suppress in at least some of the symbols the sub-carriers corresponding to a part of the transmission band to be notched;

said processor further configured

to suppress in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated, and

to multiply in a time-domain the symbols by a windowing mask configured to keep orthogonality between the sub-carriers to be transmitted and to decrease side-lobe power of the sub-carriers to be transmitted, with the windowing mask being based on a rectangular mask multiplied by an auxiliary function.

10. The device according to claim 9 , wherein said processor suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises keeping in each symbol one remaining sub-carrier every n remaining sub-carriers, with n being an integer smaller than five and suppressing all other remaining sub-carriers of the symbol.

11. The device according to claim 9 , wherein said processor suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises suppressing half of the remaining sub-carriers in each symbol.

12. The device according to claim 11 , wherein said processor suppressing in at least some of the symbols half of the remaining sub-carriers comprises suppressing every other remaining sub-carrier.

13. The device according to claim 12 , wherein said processor suppressing in at least some of the symbols every other remaining sub-carrier comprises suppressing alternately even and odd remaining sub-carriers respectively in two successive symbols.

14. The device according to claim 9 , wherein said processor further comprises:

a windowing circuit comprising a memory storing mask coefficients of the windowing mask; and

a multiplier configured to multiply in the time domain the symbols by the mask coefficients.

15. The device according to claim 9 , wherein the signal comprises an Ultra Wide Band (UWB) signal modulated according to a multiband Orthogonal Frequency-Division Multiplexing (MB-OFDM) modulation scheme.

16. A transmitter comprising:

a digital baseband stage for notching a transmission band of a digital signal including successive symbols to be transmitted, with each symbol comprising sub-carriers to be modulated, said digital baseband stage comprising:

a processor configured to suppress in at least some of the symbols the sub-carriers corresponding to a part of the transmission band to be notched,

said processor further configured

to suppress in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated, and

to multiply in a time-domain the symbols by a windowing mask configured to keep orthogonality between the sub-carriers to be transmitted and to decrease side-lobe power of the sub-carriers to be transmitted, with the windowing mask being based on a rectangular mask multiplied by an auxiliary function; and

a digital-to-analog conversion stage downstream from said digital baseband stage for converting the notched transmission band of the digital signal to an analog signal; and

an analog radio frequency stage downstream from digital-to-analog conversion stage for transmitting the notched transmission band of the analog signal.

17. The transmitter according to claim 16 , wherein said processor suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises keeping in each symbol one remaining sub-carrier every n remaining sub-carriers, with n being an integer smaller than five and suppressing all other remaining sub-carriers of the symbol.

18. The transmitter according to claim 16 , wherein said processor suppressing in at least some of the symbols a chosen part of the remaining sub-carriers to be modulated comprises suppressing half of the remaining sub-carriers in each symbol.

19. The transmitter according to claim 18 , wherein said processor suppressing in at least some of the symbols half of the remaining sub-carriers comprises suppressing every other remaining sub-carrier.

20. The transmitter according to claim 19 , wherein said processor suppressing in at least some of the symbols every other remaining sub-carrier comprises suppressing alternately even and odd remaining sub-carriers respectively in two successive symbols.

21. The transmitter according to claim 16 , wherein said processor further comprises:

a windowing circuit comprising a memory storing mask coefficients of the windowing mask; and

a multiplier configured to multiply in the time domain the symbols by the mask coefficients.

22. The transmitter according to claim 16 , wherein the signal comprises an Ultra Wide Band (UWB) signal modulated according to a multiband Orthogonal Frequency-Division Multiplexing (MB-OFDM) modulation scheme.