Claims
- 1. A method of processing a digital input signal for input to a non-linear amplifier, the method comprising:
separating the digital input signal into a plurality of digital subband signals; for each of the digital subband signals, separately converting the digital subband signal to an analog subband signal using a separate one of a first set of digital to analog converters; creating a digital correction signal based at least upon an output signal from the non-linear amplifier and the digital input signal; converting the digital correction signal to an analog correction signal using a second set of at least one digital to analog converter, wherein the second set of digital to analog converters is not included in the first set of digital to analog converters; and combining the analog subband signals and the analog correction signal to form the analog input signal.
- 2. The method of claim 1, wherein creating the digital correction signal comprises:
creating a digital predistortion signal based at least upon the digital input signal and an analog output signal from the non-linear amplifier; and removing the digital input signal from the digital predistortion signal to obtain the digital correction signal.
- 3. The method of claim 2, wherein the digital input signal based upon which the digital predistortion signal is created is formed by combining the plurality of digital subband signals.
- 4. The method of claim 1, wherein the digital input signal is a wideband signal.
- 5. A method of predistorting a digital input signal for a non-linear amplifier, the method comprising:
generating a digital correction signal based at least upon the digital input signal and an output signal from the non-linear amplifier; converting the digital input signal to at least one analog input signal; separately converting the digital correction signal to create an analog correction signal; and combining the at least one analog input signal and the analog correction signal to create an analog predistorted input signal.
- 6. The method of claim 5, wherein the at least one analog input signal comprise a plurality of analog subband input signals.
- 7. The method of claim 5, wherein the digital input signal is converted to the at least one analog input signal using at least a first digital to analog converter.
- 8. The method of claim 5, wherein the digital correction signal is converted to an analog correction signal using at least a second digital to analog converter.
- 9. The method of claim 5, wherein generating the digital correction signal comprises:
creating a digital predistortion signal based at least upon the digital input signal and the analog output signal from the non-linear amplifier; and removing the digital input signal from the digital predistortion signal to obtain the digital correction signal.
- 10. The method of claim 5, wherein converting the digital input signal to at least one analog input signal comprises:
separating the digital input signal into a plurality of digital subband input signals; processing the digital subband input signals to generate precompensated digital subband signals; and converting the precompensated digital subband signals to analog form using subband-specific digital to analog converters.
- 11. The method of claim 5, wherein the digital input signal is a wideband signal.
- 12. A method for converting a digital input signal to an analog input signal for input to a power amplifier, the method comprising:
separating the input signal into a plurality of digital subband signals; processing the digital subband signals to generate digital precompensated subband signals; converting the digital precompensated subband signals to analog form using subband-specific digital to analog converters to generate analog precompensated subband signals; and combining the analog precompensated subband signals.
- 13. The method of claim 12, wherein each of the analog precompensated subband signals is generated by further passing the output of each subband-specific digital to analog converter through a separate narrow band reconstruction filter.
- 14. The method of claim 12, further comprising:
generating an analog correction signal based at least upon the digital input signal; and combining the analog correction signal with the analog precompensated subband signals.
- 15. The method as in claim 14, wherein generating an analog correction signal comprises:
generating a predistorted digital input signal based at least upon the input signal and an output signal from the amplifier; taking a difference between the predistorted digital input signal and the digital input signal to generate a digital correction signal; and converting the digital correction signal to analog form.
- 16. The method of claim 12, wherein the digital input signal is a wideband signal.
- 17. A system for converting a digital input signal to an analog input signal for an analog amplifier, the circuit comprising:
a first circuit configured to separate the digital input signal into a plurality of digital subband input signals; a plurality of digital to analog converters, wherein each of the plurality of digital to analog converters is configured to convert one of the digital subband input signals to an analog subband input signal; and a second circuit configured to combine the analog subband input signals to form the analog input signal.
- 18. The system of claim 17, wherein the first circuit comprises a plurality of frequency demultiplexers.
- 19. The system of claim 18, wherein each of the frequency demultiplexers is selected from the group consisting of: a finite impulse response filter, an infinite impulse response filter, and a quadrature mirror filter.
- 20. The system of claim 17, wherein the first circuit comprises a plurality of bandpass filters.
- 21. The system of claim 17, wherein the first circuit comprises a plurality digital synthesizers.
- 22. The system of claim 17, wherein the first circuit further comprises a routing multiplexer.
- 23. The system of claim 17, further comprising
a plurality of correction filters, wherein each correction filter is connected between first circuit and one of the digital to analog converters, and wherein each correction filter is configured to modify at least one of the gain, the phase, and the delay of one of the digital subband input signals.
- 24. The system of claim 17, wherein the digital input signal is a wideband signal.
- 25. A circuit for predistorting a digital input signal for input to a non-linear analog amplifier, the circuit comprising:
a first circuit configured to separate the digital input signal into a plurality of digital subband input signals; a first plurality of digital to analog converters, wherein each of the first plurality of digital to analog converters is configured to convert one of the digital subband input signals to an analog subband input signal; a second circuit configured to create a digital error correction signal based at least upon an output signal from the non-linear amplifier and the digital input signal; and a second set of at least one digital to analog converters, the second set of converters configured to convert the digital error correction signal to an analog error correction signal, wherein none of the converters in the second set are included in the first plurality, wherein the analog subband input signals and the analog error correction signal are combined to form an analog input signal to the analog amplifier.
- 26. The circuit of claim 25, further comprising:
a digital compensation signal processing block configured to create a predistorted digital input signal based at least upon the digital input signal and an output signal from the non-linear amplifier; and a circuit which removes the digital input signal from the predistorted digital input signal to produce the digital error correction signal.
- 27. The circuit of claim 25, wherein the digital input signal is a wideband signal.
- 28. A system for predistorting a digital input signal to compensate for nonlinearities in an amplification process, the system comprising:
a first circuit which adaptively processes the digital input signal to compensate for at least one type of distortion introduced by the amplification process, to thereby generate a predistorted digital input signal; a second circuit which substantially removes the digital input signal from the predistorted digital input signal to generate a digital correction signal; a digital to analog converter which converts the digital correction signal to analog form to generate an analog correction signal; and a third circuit which combines the analog correction signal with at least one analog signal representing the digital input signal, to thereby generate an analog predistorted input signal.
- 29. The system as in claim 28, wherein substantially an entire dynamic range of the digital to analog converter is used to convert the digital correction signal to analog form.
- 30. The system as in claim 28, wherein the digital to analog converter is a complex pair digital to analog converter.
- 31. The system as in claim 28, further comprising a fourth circuit which generates said at least one analog signal representing the digital input signal, the fourth circuit comprising multiple signal processing paths which correspond to respective subbands of the digital input signal, each signal processing path comprising a subband-specific digital to analog converter.
- 32. The system as in claim 31, wherein each signal processing path of the fourth circuit further comprises:
a frequency demultiplexer which generates a digital subband signal from the digital input signal; and a digital filtering circuit which adaptively modifies the digital subband signal to compensate for gain, phase, and delay variations.
- 33. The system of claim 17, wherein the digital input signal is a wideband signal.
PRIORITY INFORMATION
[0001] This application claims the benefit of U.S. Provisional Application No. 60/178223, filed on Jan. 26, 2000, for “A LOW NOICE WIDEBAND DIGITAL PREDISTORTION AMPLIFIER,” which is hereby incorporated by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60178223 |
Jan 2000 |
US |