Multi-band wide band power amplifier digital predistortion system
A high performance and cost effective method of RF-digital hybrid mode power amplifier systems with high linearity and high efficiency for multi-frequency band wideband communication system applications is disclosed. The present disclosure enables a power amplifier system to be field reconfigurable and support multiple operating frequency bands on the same PA system over a very wide bandwidth. In addition, the present invention supports multi-modulation schemes (modulation agnostic), multi-carriers and multi-channels.
1. A multi-band digital predistortion system comprising
a multi-band input signal wherein the bands are centered on separate frequencies and the bandwidth of each band is substantially less than the frequency separation between the bands;
at least one power amplifier for providing an amplified output including a distortion characteristic;
input aliasing logic for creating aliased images of each band, wherein the aliased image of a first band is in one Nyquist zone and the aliased image of a second band is in another Nyquist zone, each of the one Nyquist zone and the other Nyquist zone having a width of half of a sampling rate of the input signal;
a feedback signal derived from the amplified output, including a representation of at least a portion of the distortion characteristic; and
predistortion logic responsive to the aliased images for generating predistortion coefficients for linearizing the output of the power amplifier.
2. The multi-band digital predistortion system of claim 1 , wherein the one Nyquist zone is in a first Nyquist zone, the first Nyquist zone extending from 0 Hz to half of the sampling rate of the input signal.
3. The multi-band digital predistortion system of claim 1 , wherein the other Nyquist zone is in a second Nyquist zone, the second Nyquist zone extending from half of the sampling rate of the input signal to the sampling rate of the input signal.
4. The multi-band digital predistortion system of claim 1 , wherein one band of the multi-band input signal is centered on a frequency within the one Nyquist zone and another band of the multi-band input signal is centered on a frequency within the other Nyquist zone.
5. The multi-band digital predistortion system of claim 1 , wherein the prediction logic uses an adaptive polynomial-based algorithm to generate the predistortion coefficients.
6. The multi-band digital predistortion system of claim 1 , wherein the predistortion coefficients are stored in a look-up table.
7. The multi-band digital predistortion system of claim 1 , wherein the predistortion coefficients are updated using a direct learning adaptive learning algorithm, the direct learning adaptive learning algorithm receiving as input the multi-band input signal.
8. The multi-band digital predistortion system of claim 1 , wherein the predistortion coefficients are updated using an indirect learning adaptive learning algorithm, the indirect learning adaptive learning algorithm receiving as input the aliased images.
9. The multi-band digital predistortion system of claim 1 , further comprising alignment logic to align the feedback signal with the multi-band input signal.
10. The multi-band digital predistortion system of claim 1 , further comprising a digital-to-analog converter that converts the multi-band input signal after having been processed using the predistortion coefficient to an analog signal.
11. A method for amplifying signals, the method comprising:
receiving a multi-band input signal wherein the bands are centered on separate frequencies and the bandwidth of each band is substantially less than the frequency separation between the bands;
predistorting the multi-band input signal using predistortion coefficients generated by predistortion logic, such that a first aliased image of a first band of the multi-band input signal is in one Nyquist zone and a second aliased image of a second band of the multi-band input signal is in another Nyquist band, each of the one Nyquist zone and the other Nyquist zone having a width of half of a sampling rate of the input signal
amplifying the predistorted multi-band input signal to generate an amplified output, the amplified output including a distortion characteristic,
wherein the predistortion coefficients are updated using a feedback signal derived from the amplified output, including a representation of at least a portion of the distortion characteristic.
12. The method of claim 11 , wherein the one Nyquist zone is in a first Nyquist zone, the first Nyquist zone extending from 0 Hz to half of the sampling rate of the input signal.
13. The method of claim 11 , wherein the other Nyquist zone is in a second Nyquist zone, the second Nyquist zone extending from half of the sampling rate of the input signal to the sampling rate of the input signal.
14. The method of claim 11 , wherein one band of the multi-band input signal is centered on a frequency within the one Nyquist zone and another band of the multi-band input signal is centered on a frequency within the other Nyquist zone.
15. The method of claim 11 , wherein the prediction logic uses an adaptive polynomial-based algorithm to generate the predistortion coefficients.
16. The method of claim 11 , wherein the predistortion coefficients are stored in a look-up table.
17. The method of claim 11 , further comprising:
comparing the multi-band input signal and the feedback signal using a direct learning adaptive learning algorithm; and
updating the predistortion coefficients using the comparison.
18. The method of claim 11 , further comprising:
comparing the aliased images of the multi-band input signal and the feedback signal using an indirect learning adaptive learning algorithm; and
updating the predistortion coefficients using the comparison.
19. The method of claim 11 , further comprising aligning the feedback signal with the multi-band input signal.
20. The method of claim 11 , further comprising converting the multi-band input signal from an analog signal to a digital signal after having been predistorted.