Dynamic crest factor reduction system

• US 20080247487A1
• Filed: 04/05/2007
• Published: 10/09/2008
• Est. Priority Date: 04/05/2007
• Status: Active Grant

• Current Assignee: Microelectronics Technology Inc (MTI Laboratory Inc)
• Original Assignee: Microelectronics Technology Inc (MTI Laboratory Inc)
• Inventors: Cai, Khiem V., Kent, Samuel Davis
• Granted Patent: US 7,839,951 B2
• Time in Patent Office: Days
• US Class Current: 375/296
• CPC Class Codes: H04L 27/2623 Reduction thereof by clipping

Abstract

A system and method for performing digital crest factor reduction. In one embodiment, the method is devised to suppress the signal amplitude to maintain a low signal peak to average ratio (PAR), while maintaining a desirable Error Vector Magnitude (EVM). This technique may be designed to operate in highly dynamic signal conditions.

Claims

1. A crest reduction system for gain leveling, the system comprising:

an estimator for estimating a root-mean-square (RMS) level of a first signal carrier and an RMS level of a second signal carrier, each of the first and second signal carriers having an amplitude;

a leveling setter for receiving the estimated RMS levels of the first and second signal carriers, for producing a first gain leveling factor and a second gain leveling factor for the first signal carrier by using the estimated RMS level of the first signal carrier, and for producing a third gain leveling factor and a fourth gain leveling factor for the second signal carrier by using the estimated RMS level of the second signal carrier;

a first leveler for receiving the first signal carrier and the first gain leveling factor and for changing the amplitude of the first signal carrier by adjusting the first signal carrier according to the first gain leveling factor;

a second leveler for receiving the second signal carrier and the third gain leveling factor and for changing the amplitude of the second signal carrier by adjusting the second signal carrier according to the third gain leveling factor; and

a filter configurator for receiving the second and fourth gain leveling factors, for producing one or more first filter coefficients to further change the amplitude of the first signal carrier according to the second gain leveling factor, and for producing one or more second filter coefficients to further change the amplitude of the second signal carrier according to the fourth gain leveling factor,

wherein the second gain leveling factor is substantially equal to the reciprocal of the first gain leveling factor, and

wherein the fourth gain leveling factor is substantially equal to the reciprocal of the third gain leveling factor.

2. The crest reduction system of claim 1, wherein the estimator comprises a low pass filter configured by one or more scale factors, the low pass filter being for estimating at least one of the RMS level of the first signal carrier or the RMS level of the second signal carrier.

3. The crest reduction system of claim 2, wherein the low pass filter comprises an infinite impulse response filter.

4. The crest reduction system of claim 1, wherein the first signal carrier has a first signal to distortion ratio (SDR) and the second signal carrier has a second SDR different from the first SDR.

5. The crest reduction system of claim 1,

wherein the first leveler is adapted to adjust the first signal carrier according to the first gain leveling factor by multiplying the amplitude of the first signal carrier by the first gain leveling factor.

6. The crest reduction system of claim 5,

wherein the second leveler is adapted to adjust the second signal carrier according to the third gain leveling factor by multiplying the amplitude of the second signal carrier by the third gain leveling factor.

7. The crest reduction system of claim 1,

wherein the second gain leveling factor is a multiplicative factor of at least one of the one or more first filter coefficients produced by the filter configurator.

8. The crest reduction system of claim 7,

wherein the fourth gain leveling factor is a multiplicative factor of at least one of the one or more second filter coefficients produced by the filter configurator.

9. The crest reduction system of claim 1, further comprising a leveled carrier combiner for receiving the adjusted first signal carrier from the first leveler, for receiving the adjusted second signal carrier from the second leveler, and for producing a multi-carrier signal from the adjusted first signal carrier and the adjusted second signal carrier.

10. The crest reduction system of claim 9, wherein the leveled carrier combiner is adapted to produce the multi-carrier signal by coherently combining the adjusted first signal carrier and the adjusted second signal carrier.

11. A method for gain leveling in a crest reduction system, the method comprising:

estimating a root-mean-square (RMS) level of a first signal carrier and an RMS level of a second signal carrier, each of the first and second signal carriers having an amplitude;

determining a first gain leveling factor and a second gain leveling factor for the first signal carrier by using the estimated RMS level of the first signal carrier;

determining a third gain leveling factor and a fourth gain leveling factor for the second signal carrier by using the estimated RMS level of the second signal carrier;

changing the amplitude of the first signal carrier by adjusting the first signal carrier according to the first gain leveling factor;

changing the amplitude of the second signal carrier by adjusting the second signal carrier according to the third gain leveling factor; and

determining one or more first filter coefficients to further change the amplitude of the first signal carrier according to the second gain leveling factor; and

determining one or more second filter coefficients to further change the amplitude of the second signal carrier according to the fourth gain leveling factor,

wherein the second gain leveling factor is substantially equal to the reciprocal of the first gain leveling factor, and

wherein the fourth gain leveling factor is substantially equal to the reciprocal of the third gain leveling factor.

12. The method of claim 11, wherein the estimating the RMS level of the first signal carrier and the RMS level of the second signal carrier comprises performing low pass filtering of at least one of the first and second signal carriers according to one or more scale factors.

13. The method of claim 12, wherein the performing low pass filtering comprises performing infinite impulse response filtering.

14. The method of claim 11, wherein the first signal carrier has a first signal to distortion ratio (SDR) and the second signal carrier has a second SDR different from the first SDR.

15. The method of claim 11,

wherein the adjusting the first signal carrier according to the first gain leveling factor comprises multiplying the amplitude of the first signal carrier by the first gain leveling factor.

16. The method of claim 15,

wherein the adjusting the second signal carrier according to the third gain leveling factor comprises multiplying the amplitude of the second signal carrier by the third gain leveling factor.

17. The method of claim 11,

wherein the second gain leveling factor is a multiplicative factor of at least one of the one or more first filter coefficients.

18. The method of claim 17,

wherein the fourth gain leveling factor is a multiplicative factor of at least one of the one or more second filter coefficients.

19. The method of claim 11, further comprising:

producing a multi-carrier signal from the adjusted first signal carrier and the adjusted second signal carrier.

20. The method of claim 19,

wherein the producing the multi-carrier signal comprises coherently combining the adjusted first signal carrier and the adjusted second signal carrier.

21. A crest reduction system for gain leveling, the system comprising:

means for estimating a root-mean-square (RMS) level of a first signal carrier and an RMS level of a second signal carrier, each of the first and second signal carriers having an amplitude;

means for determining a first gain leveling factor and a second gain leveling factor for the first signal carrier by using the estimated RMS level of the first signal carrier and for determining a third gain leveling factor and a fourth gain leveling factor for the second signal carrier by using the estimated RMS level of the second signal carrier;

means for changing the amplitude of the first signal carrier by adjusting the first signal carrier according to the first gain leveling factor;

means for changing the amplitude of the second signal carrier by adjusting the second signal carrier according to the third gain leveling factor; and

means for determining one or more first filter coefficients to further change the amplitude of the first signal carrier according to the second gain leveling factor and for determining one or more second filter coefficients to further change the amplitude of the second signal carrier according to the fourth gain leveling factor,

wherein the second gain leveling factor is substantially equal to the reciprocal of the first gain leveling factor, and

wherein the fourth gain leveling factor is substantially equal to the reciprocal of the third gain leveling factor.

22. The crest reduction system of claim 21, wherein the means for estimating comprises a low pass filter configured by one or more scale factors, the low pass filter being for estimating at least one of the RMS level of the first signal carrier or the RMS level of the second signal carrier.

23. The crest reduction system of claim 22, wherein the low pass filter comprises an infinite impulse response filter.

24. The crest reduction system of claim 21, wherein the first signal carrier has a first signal to distortion ration (SDR) and the second signal carrier has a second SDR different from the first SDR.

25. The crest reduction system of claim 21,

wherein the means for changing the SDR of the first signal carrier is adapted to adjust the first signal carrier according to the first gain leveling factor by multiplying the amplitude of the first signal carrier by the first gain leveling factor.

26. The crest reduction system of claim 25,

wherein the means for changing the SDR of the second signal carrier is adapted to adjust the second signal carrier according to the third gain leveling factor by multiplying the amplitude of the second signal carrier by the third gain leveling factor.

27. The crest reduction system of claim 21,

wherein the second gain leveling factor is a multiplicative factor of at least one of the one or more first filter coefficients produced by the means for determining.

28. The crest reduction system of claim 27,

wherein the fourth gain leveling factor is a multiplicative factor of at least one of the one or more second filter coefficients produced by the means for determining.

29. The crest reduction system of claim 21, further comprising means for producing a multi-carrier signal from the adjusted first signal carrier and the adjusted second signal carrier.

30. The crest reduction system of claim 29, wherein the means for producing is adapted to produce the multi-carrier signal by coherently combining the adjusted first signal carrier and the adjusted second signal carrier.

31. A crest reduction system for amplitude limiting, the system comprising:

a controller for receiving a first signal including one or more signal carriers, for determining a signal to distortion ratio (SDR) of the first signal, and for producing a correction value by using the determined SDR and a threshold SDR; and

a dynamic amplitude clipper for receiving the correction value and a second signal corresponding to the first signal and for producing a clipped signal by limiting an amplitude of the second signal according to a value corresponding to the correction value such that a peak to average ratio (PAR) of the clipped signal is not greater than a PAR of the second signal,

wherein the clipped signal has phase characteristics substantially equal to phase characteristics of the second signal.

32. The crest reduction system of claim 31, further comprising:

a second dynamic amplitude clipper coupled with the dynamic amplitude clipper, the second dynamic amplitude clipper being for receiving the correction value and a third signal corresponding to the clipped signal and for producing a second clipped signal by limiting an amplitude of the third signal according to a second value corresponding to the correction value such that a PAR of the second clipped signal is not greater than a PAR of the third signal,

wherein the second clipped signal has phase characteristics substantially equal to phase characteristics of the third signal.

33. The crest reduction system of claim 32,

wherein the phase characteristics of the second clipped signal are substantially equal to phase characteristics of the clipped signal.

34. The crest reduction system of claim 32,

wherein the dynamic amplitude clipper comprises an estimator for estimating a root-mean-square (RMS) level of the second signal,

wherein the value corresponding to the correction value further corresponds to the estimated RMS level of the second signal such that the PAR of the clipped signal is substantially constant over time,

wherein the second dynamic amplitude clipper comprises an estimator for estimating an RMS level of the third signal, and

wherein the second value corresponding to the correction value further corresponds to the estimated RMS level of the third signal such that the PAR of the second clipped signal is substantially constant over time.

35. The crest reduction system of claim 31,

wherein the dynamic amplitude clipper comprises an estimator for estimating a root-mean-square (RMS) level of the second signal, and

wherein the value corresponding to the correction value further corresponds to the estimated RMS level of the second signal such that the PAR of the clipped signal is substantially constant over time.

36. The crest reduction system of claim 35,

wherein the estimator for estimating the power of the second signal comprises an infinite impulse response filter.

37. The crest reduction system of claim 31, further comprising:

a gain corrector for receiving a third signal corresponding to the clipped signal and for reducing an energy loss of the third signal resulting from the limiting of the amplitude of the second signal by the dynamic amplitude clipper.

38. The crest reduction system of claim 31,

wherein the dynamic amplitude clipper is adapted to be controlled to produce an unclipped signal from the second signal, and

wherein a PAR of the unclipped signal is substantially equal to the PAR of the second signal.

39. The crest reduction system of claim 38, further comprising:

a timing and control unit for controlling the dynamic amplitude clipper to produce the unclipped signal.

40. The crest reduction system of claim 31,

wherein the dynamic amplitude clipper comprises:

a first multiplier for multiplying the second signal and an inverse of the value corresponding to the correction value; and

a second multiplier for producing the clipped signal by multiplying a third signal corresponding to the second signal and the value corresponding to the correction value.

41. A method for amplitude limiting in a crest reduction system, the method comprising:

receiving a first signal including one or more signal carriers;

determining a signal to distortion ratio (SDR) of the first signal;

producing a correction value by using the determined SDR and a threshold SDR;

producing a second signal corresponding to the first signal; and

producing a clipped signal by limiting an amplitude of the second signal according to a value corresponding to the correction value such that a peak to average ratio (PAR) of the clipped signal is not greater than a PAR of the second signal,

wherein the clipped signal has phase characteristics substantially equal to phase characteristics of the second signal.

42. The method of claim 41, further comprising:

producing a third signal corresponding to the clipped signal; and

producing a second clipped signal by limiting an amplitude of the third signal according to the value corresponding to the correction value such that a peak to average ratio (PAR) of the second clipped signal is not greater than a PAR of the third signal,

wherein the second clipped signal has phase characteristics substantially equal to phase characteristics of the third signal.

43. The method of claim 42,

wherein the phase characteristics of the second clipped signal are substantially equal to phase characteristics of the clipped signal.

44. The method of claim 42,

wherein the producing the clipped signal comprises estimating a root-mean-square (RMS) level of the second signal,

wherein the value corresponding to the correction value further corresponds to the estimated RMS level of the second signal such that the PAR of the clipped signal is substantially constant over time,

wherein the producing the second clipped signal comprises estimating an RMS level of the third signal, and

wherein the second value corresponding to the correction value further corresponds to the estimated RMS level of the third signal such that the PAR of the clipped signal is substantially constant over time.

45. The method of claim 41,

wherein the producing the clipped signal comprises estimating a root-mean-square (RMS) level of the second signal, and

wherein the value corresponding to the correction value further corresponds to the estimated RMS level of the second signal such that the PAR of the clipped signal is substantially constant over time.

46. The method of claim 45,

wherein the estimating the power of the second signal comprises performing infinite impulse response filtering.

47. The method of claim 41, further comprising:

producing a third signal corresponding to the clipped signal; and

reducing an energy loss of the third signal resulting from the limiting of the amplitude of the second signal.

48. The method of claim 41,

wherein the producing the clipped signal comprises detecting one or more commands to produce an unclipped signal from the second signal, and

wherein a PAR of the unclipped signal is substantially equal to the PAR of the second signal.

49. The method of claim 48, further comprising:

commanding the production of the unclipped signal.

50. The method of claim 41,

wherein the producing the clipped signal comprises:

multiplying the second signal and an inverse of the value corresponding to the correction value; and

producing the clipped signal by multiplying a third signal corresponding to the second signal and the value corresponding to the correction value.

51. A crest reduction system for amplitude limiting, the system comprising:

means for receiving a first signal including one or more signal carriers, for determining a signal to distortion ratio (SDR) of the first signal, and for producing a correction value by using the determined SDR and a threshold SDR; and

means for producing a second signal corresponding to the first signal, for producing a clipped signal by limiting an amplitude of the second signal according to a value corresponding to the correction value such that a peak to average ratio (PAR) of the clipped signal is not greater than a PAR of the second signal,

wherein the clipped signal has phase characteristics substantially equal to phase characteristics of the second signal.

52. The crest reduction system of claim 51, further comprising:

means for producing a third signal corresponding to the clipped signal;

means for producing a second clipped signal by limiting an amplitude of the third signal according to the value corresponding to the correction value such that a peak to average ratio (PAR) of the second clipped signal is not greater than a PAR of the third signal, the means for producing the second clipped signal being coupled with the means for producing the second signal,

wherein the second clipped signal has phase characteristics substantially equal to phase characteristics of the third signal.

53. The crest reduction system of claim 52,

wherein the phase characteristics of the second clipped signal are substantially equal to phase characteristics of the clipped signal.

54. The crest reduction system of claim 52,

wherein the means for producing the second signal comprises an estimator for estimating a root-mean-square (RMS) level of the second signal,

wherein the value corresponding to the correction value further corresponds to the estimated RMS level of the second signal such that the PAR of the clipped signal is substantially constant over time,

wherein the means for producing the third signal comprises an estimator for estimating an RMS level of the third signal,

wherein the second value corresponding to the correction value further corresponds to the estimated RMS level of the third signal such that the PAR of the clipped signal is substantially constant over time.

55. The crest reduction system of claim 51,

wherein the means for producing the second signal comprises an estimator for estimating a root-mean-square (RMS) level of the second signal, and

wherein the value corresponding to the correction value further corresponds to the estimated RMS level of the second signal such that the PAR of the clipped signal is substantially constant over time.

56. The crest reduction system of claim 55,

wherein the estimator for estimating the RMS level of the second signal comprises an infinite impulse response filter.

57. The crest reduction system of claim 51, further comprising:

means for producing a third signal corresponding to the clipped signal; and

means for reducing an energy loss of the third signal resulting from the limiting of the amplitude of the second signal.

58. The crest reduction system of claim 51,

wherein the means for producing the second signal is adapted to be controlled to produce an unclipped signal from the second signal, and

wherein a PAR of the unclipped signal is substantially equal to the PAR of the second signal.

59. The crest reduction system of claim 58, further comprising:

means for controlling the means for producing the second signal to produce the unclipped signal.

60. The crest reduction system of claim 51,

wherein the means for producing the second signal comprises:

a first multiplier for multiplying the second signal and an inverse of the value corresponding to the correction value; and

a second multiplier for producing the clipped signal by multiplying a third signal corresponding to the second signal and the value corresponding to the correction value.

61. A crest reduction system for composite filtering, the system comprising:

a timing and control unit for receiving a first signal including a plurality of signal carriers and for processing a detected absence of one or more of the signal carriers;

a filter configurator for producing a plurality of composite coefficients for filtering of the signal, each of the composite coefficients being formed from a plurality of coefficients, and for zeroing one or more of the coefficients corresponding to the one or more signal carriers in response to the detected absence of the one or more signal carriers; and

a filter generator for receiving the composite coefficients and for implementing a filter for a second signal corresponding to the first signal, the filter being configured to output a third signal by filtering the second signal according to the composite coefficients.

62. The crest reduction system of claim 61,

wherein the filter is further configured to output the third signal by substantially filtering out one or more frequency components of the second signal corresponding to the zeroed one or more of the coefficients.

63. The crest reduction system of claim 61,

wherein the filter configurator comprises a plurality of multiplexer units, each of the multiplexer units being adapted to receive one or more of the coefficients corresponding to one of the signal carriers and to output either the one or more of the coefficients or one or more zero value coefficients in response to the detected absence of the one of the signal carriers.

64. The crest reduction system of claim 63,

wherein the filter configurator further comprises a combiner for receiving the respective outputs of the multiplexer units and for producing the composite coefficients by linearly combining the respective outputs.

65. The crest reduction system of claim 61, further comprising:

a second filter generator for receiving the composite coefficients and for implementing a second filter for a fourth signal corresponding to the third signal, the second filter being configured to output a fifth signal by filtering the fourth signal according to the composite coefficients.

66. The crest reduction system of claim 65,

wherein the second filter is further configured to output the fifth signal by substantially filtering out one or more frequency components of the fourth signal corresponding to the zeroed one or more of the coefficients.

67. The crest reduction system of claim 61,

wherein a first one of the signal carriers has a first passband,

wherein a second one of the signal carriers has a second passband, the first passband and the second passband forming a frequency well therebetween, and

wherein the filter configurator further is for producing a plurality of nibble coefficients for the filtering of the signal, the nibble coefficients being configured to substantially fill the frequency well.

68. The crest reduction system of claim 67,

wherein the filter configurator comprises a multiplexer unit adapted to receive one or more of the nibble coefficients corresponding to the first one of the signal carriers and the second one of the signal carriers and to output either the one or more of the nibble coefficients or one or more zero value coefficients in response to the detected absence of at least one of the first one of the signal carriers or the second one of the signal carriers.

69. A method for composite filtering in a crest reduction system, the method comprising:

receiving a first signal including a plurality of signal carriers;

processing a detected absence of one or more of the signal carriers;

producing a plurality of composite coefficients for filtering of the signal, each of the composite coefficients being formed from a plurality of coefficients;

zeroing one or more of the coefficients corresponding to the one or more signal carriers in response to the detected absence of the one or more signal carriers; and

implementing a filter for a second signal corresponding to the first signal, the filter being configured to output a third signal by filtering the second signal according to the composite coefficients.

70. The method of claim 69,

wherein the filter is further configured to output the third signal by substantially filtering out one or more frequency components of the second signal corresponding to the zeroed one or more of the coefficients.

71. The method of claim 69,

wherein the producing the composite coefficients comprises receiving one or more of the coefficients corresponding to one of the signal carriers and outputting either the one or more of the coefficients or one or more zero value coefficients in response to the detected absence of the one of the signal carriers.

72. The method of claim 71,

wherein the producing the composite coefficients further comprises linearly combining the outputted either the one or more of the coefficients or one or more zero value coefficients and one or more of the coefficients corresponding to another of the signal carriers.

73. The method of claim 69, further comprising:

producing a fourth signal corresponding to the third signal; and

implementing a second filter for the fourth signal, the second filter being configured to output a fifth signal by filtering the fourth signal according to the composite coefficients.

74. The method of claim 73,

wherein the second filter is further configured to output the fifth signal by substantially filtering out one or more frequency components of the fourth signal corresponding to the zeroed one or more of the coefficients.

75. The method of claim 69,

wherein a first one of the signal carriers has a first passband,

wherein a second one of the signal carriers has a second passband, the first passband and the second passband forming a frequency well therebetween, and

wherein the method further comprises producing a plurality of nibble coefficients for the filtering of the signal, the nibble coefficients being configured to substantially fill the frequency well.

76. The method of claim 75,

wherein the producing the composite nibble coefficient comprises outputting either the one or more of the nibble coefficients or one or more zero value coefficients in response to the detected absence of at least one of the first one of the signal carriers or the second one of the signal carriers.

77. A crest reduction system for composite filtering, the system comprising:

means for receiving a first signal including a plurality of signal carriers and for processing a detected absence of one or more of the signal carriers;

means for producing a plurality of composite coefficients for filtering of the signal, each of the composite coefficients being formed from a plurality of coefficients, and for zeroing one or more of the coefficients corresponding to the one or more signal carriers in response to the detected absence of the one or more signal carriers; and

means for implementing a filter for a second signal corresponding to the first signal, the filter being configured to output a third signal by filtering the second signal according to the composite coefficients.

78. The crest reduction system of claim 77,

wherein the filter is further configured to output the third signal by substantially filtering out one or more frequency components of the second signal corresponding to the zeroed one or more of the coefficients.

79. The crest reduction system of claim 77,

wherein the means for implementing the filter comprises a plurality of multiplexer units, each of the multiplexer units being adapted to receive one or more of the coefficients corresponding to one of the signal carriers and to output either the one or more of the coefficients or one or more zero value coefficients in response to the detected absence of the one of the signal carriers.

80. The crest reduction system of claim 79,

wherein the means for implementing the filter further comprises a combiner for receiving the respective outputs of the multiplexer units and for producing the composite coefficients by linearly combining the respective outputs.

81. The crest reduction system of claim 77, further comprising:

means for implementing a second filter for a fourth signal corresponding to the third signal, the second filter being configured to output a fifth signal by filtering the fourth signal according to the composite coefficients.

82. The crest reduction system of claim 81,

wherein the second filter is further configured to output the fifth signal by substantially filtering out one or more frequency components of the fourth signal corresponding to the zeroed one or more of the coefficients.

83. The crest reduction system of claim 77,

wherein a first one of the signal carriers has a first passband,

wherein a second one of the signal carriers has a second passband, the first passband and the second passband forming a frequency well therebetween, and

wherein the means for implementing the filter is further for producing a plurality of nibble coefficients for the filtering of the signal, the nibble coefficients being configured to substantially fill the frequency well.

84. The crest reduction system of claim 83,

wherein the means for implementing the filter comprises a multiplexer unit adapted to receive one or more of the nibble coefficients corresponding to the first one of the signal carriers and the second one of the signal carriers and to output either the one or more of the nibble coefficients or one or more zero value coefficients in response to the detected absence of at least one of the first one of the signal carriers or the second one of the signal carriers.

85. A crest reduction system comprising:

a controller for receiving a first frequency and a first bandwidth of a first baseband symbol stream and for receiving a second frequency and a second bandwidth of a second baseband symbol stream;

a first carrier processor for receiving the first baseband symbol stream and for converting the first baseband symbol stream to a first signal having the first bandwidth centered about the first frequency;

a second carrier processor for receiving the second baseband symbol stream and for converting the second baseband symbol stream to a second signal having the second bandwidth centered about the second frequency; and

one or more signals processors for receiving the first and second signals and for adjusting a respective signal to distortion ratio (SDR) of each of the first and second signals while a peak to average ratio (PAR) of a composite signal produced from the first and second signals is reduced.

86. The crest reduction system of claim 85,

wherein the first frequency has a value different from a value of the second frequency.

87. The crest reduction system of claim 86,

wherein the first bandwidth has a frequency range different from a frequency range of the second bandwidth.

88. The crest reduction system of claim 85,

wherein the first bandwidth has a frequency range substantially equal to a frequency range of the second bandwidth.

89. The crest reduction system of claim 85,

wherein the first baseband symbol stream corresponds to a WCDMA signal, and

wherein the second baseband symbol stream corresponds to a cdma2000 signal.

90. The crest reduction system of claim 85, further comprising:

a combiner for receiving the first and second signals and for producing a multi-carrier signal from the first and second signals.

91. The crest reduction system of claim 90,

wherein the combiner is adapted to produce the multi-carrier signal by coherently combining the first and second signals.

92. The crest reduction system of claim 85,

wherein the first carrier processor is adapted to increase a sample rate of the first baseband symbol stream according to a first rate to produce a first intermediate signal,

wherein the second carrier processor is adapted to increase a sample rate of the second baseband symbol stream according to a second rate to produce a second intermediate signal,

wherein the first rate has a value different from a value of the second rate,

wherein the first carrier processor comprises a first resampler for resampling the first intermediate signal according to a third rate to produce the first signal, and

wherein the second carrier processor comprises a second resampler for resampling the second intermediate signal according to a fourth rate substantially equal to the third rate to produce the second signal.

93. A method of signal converting in a crest reduction system, the method comprising:

receiving a first frequency and a first bandwidth corresponding to a first baseband symbol stream;

receiving a second frequency and a second bandwidth corresponding to a second baseband symbol stream;

converting the first baseband symbol stream to a first signal having the first bandwidth centered about the first frequency;

converting the second baseband symbol stream to a second signal having the second bandwidth centered about the second frequency; and

adjusting a respective signal to distortion ratio (SDR) of each of the first and second signals while a peak to average ratio (PAR) of a composite signal produced from the first and second signals is reduced.

94. The method of claim 93,

wherein the first frequency has a value different from a value of the second frequency.

95. The method of claim 94,

wherein the first bandwidth has a frequency range different from a frequency range of the second bandwidth.

96. The method of claim 93,

wherein the first bandwidth has a frequency range substantially equal to a frequency range of the second bandwidth.

97. The method of claim 93,

wherein the first baseband symbol stream corresponds to a WCDMA signal, and

wherein the second baseband symbol stream corresponds to a cdma2000 signal.

98. The method of claim 93, further comprising:

producing a multi-carrier signal from the first and second signals.

99. The method of claim 98,

wherein the producing the multi-carrier signal comprises coherently combining the first and second signals.

100. The method of claim 93,

wherein the converting the first baseband symbol stream comprises increasing a sample rate of the first baseband symbol stream according to a first rate to produce a first intermediate signal,

wherein the converting the second baseband symbol stream comprises increasing a sample rate of the second baseband symbol stream according to a second rate to produce a second intermediate signal,

wherein the first rate has a value different from a value of the second rate,

wherein the converting the first baseband symbol stream further comprises resampling the first intermediate signal according to a third rate to produce the first signal, and

wherein the converting the second baseband symbol stream further comprises resampling the second intermediate signal according to a fourth rate substantially equal to the third rate to produce the second signal.

101. A crest reduction system comprising:

means for receiving a first frequency and a first bandwidth corresponding to a first baseband symbol stream and for receiving a second frequency and a second bandwidth corresponding to a second baseband symbol stream;

means for converting the first baseband symbol stream to a first signal having the first bandwidth centered about the first frequency;

means for converting the second baseband symbol stream to a second signal having the second bandwidth centered about the second frequency; and

means for adjusting a respective signal to distortion ratio (SDR) of each of the first and second signals while a peak to average ratio (PAR) of a composite signal produced from the first and second signals is reduced.

102. The crest reduction system of claim 101,

wherein the first frequency has a value different from a value of the second frequency.

103. The crest reduction system of claim 102,

wherein the first bandwidth has a frequency range different from a frequency range of the second bandwidth.

104. The crest reduction system of claim 101,

wherein the first bandwidth has a frequency range substantially equal to a frequency range of the second bandwidth.

105. The crest reduction system of claim 101,

wherein the first baseband symbol stream corresponds to a WCDMA signal, and

wherein the second baseband symbol stream corresponds to a cdma2000 signal.

106. The crest reduction system of claim 101, further comprising:

means for receiving the first and second signals and for producing a multi-carrier signal from the first and second signals.

107. The crest reduction system of claim 106,

wherein the means for receiving the first and second signals is adapted to produce the multi-carrier signal by coherently combining the first and second signals.

108. The crest reduction system of claim 101,

wherein the means for converting the first baseband symbol stream is adapted to increase a sample rate of the first baseband symbol stream according to a first rate to produce a first intermediate signal,

wherein the means for converting the second baseband symbol stream is adapted to increase a sample rate of the second baseband symbol stream according to a second rate to produce a second intermediate signal,

wherein the first rate has a value different from a value of the second rate,

wherein the means for converting the first baseband symbol stream comprises a first resampler for resampling the first intermediate signal according to a third rate to produce the first signal, and

wherein the means for converting the second baseband symbol stream comprises a second resampler for resampling the second intermediate signal according to a fourth rate substantially equal to the third rate to produce the second signal.