Method and Apparatus for Modifying a Characteristic of a Complex-Valued Signal

• US 20110156832A1
• Filed: 12/29/2009
• Published: 06/30/2011
• Est. Priority Date: 12/29/2009
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Mobile Communications GmbH (Intel Corporation)
• Inventors: Menkhoff, Andreas
• Granted Patent: US 8,717,116 B2
• Time in Patent Office: Days
• US Class Current: 332/117
• CPC Class Codes: H04L 27/3405 Modifications of the signal space to increase the efficiency of transmission, e.g. reduction of the bit error rate, bandwidth, or average power
• CPC Class Codes: H04L 27/364 Arrangements for overcoming imperfections in the modulator, e.g. quadrature error or unbalanced I and Q levels
• CPC Class Codes: H04L 27/367 using predistortion

Abstract

A method for modifying a characteristic of a representation of a complex-valued signal which comprises at least a representation of a first and a second complex-valued symbol comprising deriving a relative phase angle between the representation of the first and the second complex-valued symbols. The method further comprises combining a representation of a complex-valued enhancement pulse and the representation of the complex-valued signal to obtain a representation of a first and a second corrected complex-valued symbol, wherein the enhancement pulse is chosen such that the relative phase angle between the first and second corrected symbols is smaller than a predetermined threshold.

Claims

1. A method for modifying a characteristic of a representation of a complex-valued signal, the signal comprising at least a representation of a first and a second complex-valued symbol, the method comprising:

deriving a relative phase angle between the representation of the first and the second complex-valued symbols; and

combining a representation of a complex-valued enhancement pulse and the representation of the complex-valued signal to obtain a representation of a first and a second corrected complex-valued symbol, wherein the enhancement pulse is chosen such that the relative phase angle between the first and second corrected symbols is smaller than a predetermined threshold.

2. The method according to claim 1, wherein the combining comprises adding a complex-valued enhancement symbol to the first or to the second complex-valued symbol.

3. The method according to claim 1, wherein the combining comprises adding a first enhancement pulse to a representation of a real part of the complex-valued signal;

or

adding a second enhancement pulse to a representation of an imaginary part of the complex-valued signal.

4. The method according to claim 1, wherein the combining comprises adding a complex-valued enhancement pulse to the complex-valued signal.

5. The method according to claim 1, wherein the combining comprises adding a third enhancement pulse to a representation of a phase of the complex-valued signal;

or

adding a fourth enhancement pulse to a representation of a magnitude of the complex-valued signal.

6. The method according to claim 1, wherein the representation of the complex-valued enhancement pulse is chosen such that a magnitude of the enhancement pulse is greater for a first pair of first and second complex-valued symbols with a greater magnitude than for a second pair of first and second complex-valued symbols having a lower magnitude.

7. The method according to claim 1, further comprising:

comparing the relative phase angle and the predetermined threshold, wherein the combining is only performed when the relative phase angle exceeds the predetermined threshold.

8. The method according to claim 1, further comprising:

inputting the first and second corrected symbols into a high frequency modulator for providing a high frequency carrier signal having modulated thereon the representation of the first and second corrected symbols.

9. The method according to claim 1, wherein the representation of the complex-valued signal comprises a sequence of representations of complex-valued symbols, comprising:

deriving a relative phase angle between each pair of neighboring complex-valued symbols within the sequence; and

combining a complex-valued enhancement pulse with the representation of the complex-valued signal for every pair of neighboring symbols having a relative phase angle exceeding the predetermined threshold.

10. The method according to claim 9, wherein the representation of the complex-valued enhancement pulse is chosen such that the length of the enhancement pulse depends on the number of symbols occurring between two consecutive pairs of neighboring symbols exceeding the threshold.

11. The method according to claim 10, wherein the enhancement pulse is shorter for a smaller number of symbols occurring between the two consecutive pairs of symbols than for a higher number of symbols occurring between the two consecutive pairs of symbols.

12. The method according to claim 1, wherein the representation of the complex-valued signal is a representation of a base band of a communication signal.

13. An apparatus for modifying the characteristic of a representation of a complex-valued signal, the signal comprising at least a representation of a first and a second complex-valued symbol, the apparatus comprising:

an analyzer adapted to derive a relative phase angle between the representation of the first and the second complex-valued symbols; and

a signal enhancer adapted to combine a representation of a complex-valued enhancement pulse and the representation of the complex-valued signal to obtain a representation of a first and a second corrected complex-valued symbol, wherein the enhancement pulse is chosen such that a relative phase angle between the first and second corrected symbols is smaller than a predetermined threshold.

14. The apparatus according to claim 13, wherein the signal enhancer is adapted to add a complex-valued enhancement symbol to the first or to the second complex-valued symbol.

15. The apparatus according to claim 13, wherein the signal enhancer is adapted to add a first enhancement pulse to a representation of a real part of the complex-valued signal;

or

to add a second enhancement pulse to a representation of an imaginary part of the complex-valued signal.

16. The apparatus according to claim 13, wherein the signal enhancer is adapted to add a complex-valued enhancement pulse to the complex-valued signal.

17. The apparatus according to claim 13, wherein the signal enhancer is adapted to add a third enhancement pulse to a representation of a phase of the complex-valued signal;

or

to add a fourth enhancement pulse to a representation of a magnitude of the complex-valued signal.

18. The apparatus according to claim 13, wherein the signal enhancer is adapted to choose the enhancement pulse such that the magnitude of the enhancement pulse is greater for a first pair of first and second complex-valued symbols with a greater magnitude than for a second pair of first and second complex-valued symbols having a lower magnitude.

19. The apparatus according to claim 13 adapted to modify a representation of a complex-valued signal comprising a sequence of representations of complex-valued symbols, wherein

the analyzer is adapted to derive a relative phase angle between the representation of the first and the second complex-valued symbols;

and

wherein the signal enhancer is adapted to combine a complex-valued enhancement pulse with the representation of the complex-valued signal for every pair of neighboring symbols having a relative phase angle exceeding the predetermined threshold.

20. The apparatus according to claim 13, wherein the signal enhancer is adapted to choose the enhancement pulse such that the length of the enhancement pulse depends on the number of symbols occurring between two consecutive pairs of neighboring symbols exceeding the threshold.

21. The apparatus according to claim 20, wherein the signal enhancer is adapted to choose the enhancement pulse such that the enhancement pulse is shorter for a smaller number of symbols occurring between the two consecutive pairs of symbols than for a higher number of symbols occurring between the two consecutive pairs of symbols.

22. The apparatus according to claim 13, further comprising:

a high-frequency modulator adapted to modulate the representation of the first and second corrected symbols on a high frequency carrier signal to provide a modulated carrier signal.

23. The apparatus according to claim 22, wherein the apparatus is embedded in a high-frequency transmitter.

24. The apparatus according to claim 22, wherein the high-frequency modulator is an R/φ

modulator.

25. A method for modifying the characteristic of a representation of a complex-valued base-band signal usable as an input to a high-frequency modulator, the method comprising:

deriving an instantaneous frequency of the representation of the complex-valued base-band signal;

comparing the derived instantaneous frequency with a predetermined upper threshold; and

when the derived instantaneous frequency exceeds the threshold, combining a representation of a complex-valued enhancement pulse and the representation of the base-band signal in order to provide a representation of a corrected base-band signal, wherein the representation of the enhancement pulse is chosen such that the instantaneous frequency of the representation of the corrected base-band signal is below the threshold.

26. The method according to claim 25, wherein deriving the instantaneous frequency comprises:

determining a relative phase angle between a representation of a first and a second sampled complex-valued symbol of the base-band signal.

27. The method according to claim 25, further comprising:

inputting the representation of the corrected base-band signal to a high-frequency modulator for providing a high-frequency carrier signal having modulated thereon the representation of the corrected base-band signal.

28. An apparatus for modifying the characteristic of a representation of a complex-valued base-band signal usable as an input to a high-frequency modulator, the apparatus comprising:

a frequency analyzer adapted to derive an instantaneous frequency of the representation of the complex-valued base-band signal;

a comparator adapted to compare the derived instantaneous frequency with a predetermined upper threshold; and

a signal combiner adapted to combine, when the derived instantaneous frequency exceeds the threshold, a representation of a complex-valued enhancement pulse and the representation of the base-band signal in order to provide a representation of a corrected base-band signal, wherein the representation of the enhancement pulse is chosen such that the instantaneous frequency of the representation of the corrected base-band signal is below the threshold.

29. The apparatus of claim 28, further comprising:

a high-frequency modulator adapted to modulate the representation of the corrected base-band signal on a high-frequency carrier signal to provide a modulated carrier signal.

30. An apparatus for modifying the characteristic of a representation of a complex-valued signal, the signal comprising at least a representation of a first and a second complex-valued symbol, the apparatus comprising:

means for deriving a relative phase angle between the representation of the first and the second complex-valued symbols; and

means for combining a representation of a complex-valued enhancement pulse and the representation of the complex-valued signal to obtain a representation of a first and a second corrected complex-valued symbol, wherein the enhancement pulse is chosen such that the relative phase angle between the first and second corrected symbols is smaller than a predetermined threshold.

31. The apparatus of claim 30, further comprising:

means for modulating the representation of the corrected base-band signal on a high-frequency carrier signal to provide a modulated carrier signal.