System and method to implement a radio transmitter with digital predistortion having reduced noise

1. A radio transmitter having reduced noise comprising:

a power amplifier;

a digital predistortion arrangement to apply digital predistortion to a transmit signal having a narrowband component, the digital predistortion arrangement generating a predistortion signal having the narrowband component and a wideband component;

a first upconverter to upconvert the narrowband component; and

a second upconverter to upconvert the wideband component;

wherein outputs of the first and second upconverters are summed, the sum being transmitted to the power amplifier.

2. The radio transmitter according to claim 1 , wherein the digital predistortion is set by coefficients determined by a digital predistortion algorithm.

3. The radio transmitter according to claim 2 , wherein the coefficients are determined by the digital predistortion algorithm to minimize a difference between the transmit signal and an output of the power amplifier.

4. The radio transmitter according to claim 1 , wherein the wideband component of the predistortion signal includes digital predistortion correction products.

5. The radio transmitter according to claim 1 , further comprising:

an equalization arrangement to correct at least one of a phase difference, a group delay, and an amplitude response between the narrowband component and the wideband component.

6. The radio transmitter according to claim 5 , wherein the equalization arrangement is set by a downconverter monitoring an output of the power amplifier.

7. The radio transmitter according to claim 1 , wherein the first upconverter includes a digital-to-analog converter.

8. The radio transmitter according to claim 1 , wherein the first upconverter includes a filter.

9. The radio transmitter according to claim 1 , wherein the first upconverter includes a modulator to modulate the narrowband component with a varying signal.

10. The radio transmitter according to claim 9 , wherein the varying signal is a sinusoid or square wave carrier.

11. The radio transmitter according to claim 1 , further comprising:

an amplifier to correct a gain difference between the first and the second upconverter.

12. The radio transmitter according to claim 1 , further comprising:

a downconverter to monitor an output of the power amplifier.

13. The radio transmitter according to claim 1 , wherein the second upconverter includes a digital-to-analog converter.

14. The radio transmitter according to claim 1 , wherein the second upconverter includes a filter.

15. The radio transmitter according to claim 1 , wherein the second upconverter includes a modulator to modulate the wideband component with a varying signal.

16. The radio transmitter according to claim 15 , wherein the varying signal is a sinusoid or square wave carrier.

17. The radio transmitter according to claim 1 , wherein the sum is modulated by a modulator before being transmitted to the power amplifier.

18. A method for reducing noise due to distortion in a radio transmitter, the method comprising:

generating a predistortion signal from an application of digital predistortion coefficients to a transmit signal having a narrowband component;

separating the predistortion signal into the narrowband component and a wideband component;

correcting for at least one of a phase difference, a group delay, and an amplitude response between the narrowband component and the wideband component;

upconverting the narrowband component to a higher frequency through modulation with a varying signal by a first upconverter;

upconverting the wideband component to the higher frequency through modulation with the varying signal by a second upconverter;

summing an upconverted narrowband component and an upconverted wideband component; and

outputting the sum to a power amplifier.

19. The method according to claim 18 , wherein the digital predistortion coefficients are determined by a digital predistortion algorithm.

20. The method according to claim 19 , wherein the digital predistortion coefficients are determined by the digital predistortion algorithm to minimize a difference between the transmit signal and an output of the power amplifier.

21. The method according to claim 18 , wherein the wideband component of the predistortion signal includes digital predistortion correction products.

22. The method according to claim 18 , wherein the first upconverter includes a filter.

23. The method according to claim 18 , further comprising:

amplifying the narrowband component of the predistortion signal to correct a gain difference between the first and the second upconverter.

24. The method according to claim 18 , further comprising:

monitoring an output of the power amplifier with a downconverter.

25. The method according to claim 18 , wherein the varying signal is a sinusoid or square wave carrier.

26. The method according to claim 18 , wherein the second upconverter includes a filter.

27. A method for reducing noise due to distortion in a radio transmitter, the method comprising:

generating a predistortion signal from an application of digital predistortion coefficients to a transmit signal having a narrowband component;

separating the predistortion signal into the narrowband component and a wideband component;

correcting for at least one of a phase difference, group delay, and amplitude response between the narrowband component and the wideband component;

filtering the narrowband component with a first filter in a first upconverter;

filtering the wideband component with a second filter in a second upconverter;

summing the filtered narrowband component and the filtered wideband component;

modulating the sum with a varying signal by a modulator; and

outputting the modulated sum to a power amplifier.