System and method for increasing bandwidth for digital predistortion in multi-channel wideband communication systems
A method of operating a communications system includes receiving a signal at a digital predistorter (DPD), introducing predistortion to the signal using the DPD, and converting the predistorted signal to an analog signal using a digital-to-analog converter having a first bandwidth. The method also includes amplifying the analog signal, sampling the amplified signal using an analog-to-digital converter having a second bandwidth less than the first bandwidth, and extracting coefficients of the DPD from the sampled signal.
1. A method of operating a communications system, the method comprising:
receiving a signal at a digital predistorter (DPD) having a DPD bandwidth;
introducing predistortion to the signal using the DPD;
converting the predistorted signal to an analog signal using a digital-to-analog converter having a first bandwidth;
modulating the analog signal using a modulator;
amplifying the modulated signal;
filtering the amplified signal using a duplexer having a duplexer bandwidth less than the first bandwidth;
transmitting the filtered signal using an antenna;
sampling the amplified signal using an analog-to-digital converter having a second bandwidth less than the first bandwidth; and
extracting coefficients of the DPD from the sampled signal.
2. The method of claim 1 , further comprising up-converting the modulated signal.
3. The method of claim 1 , further comprising filtering the amplified signal using a bandpass filter.
4. The method of claim 3 , wherein the bandpass filter has a filter bandwidth less than the DPD bandwidth.
5. The method of claim 1 , further comprising downconverting the amplified signal.
6. The method of claim 1 , wherein converting the predistorted signal to the analog signal is performed at a sampling rate less than twice a DPD bandwidth.
7. A communications system comprising:
a digital predistorter (DPD) configured to predistort an input signal and to produce a DPD output signal having a DPD bandwidth;
a digital-to-analog converter having a first bandwidth, the digital-to-analog converter configured to convert the DPD output signal to an analog signal;
a modulator configured to modulate the analog signal;
a power amplifier configured to amplify the modulated analog signal to produce a power amplifier output signal;
a duplexer configured to filter the power amplifier output signal to produce a filtered signal, wherein the duplexer has a duplexer bandwidth less than the first bandwidth;
an antenna configured to transmit the filtered signal; and
an analog-to-digital converter having a second bandwidth less than the first bandwidth, the analog-to-digital converter configured to convert the power amplifier output signal to a digital signal,
wherein the digital signal includes coefficients configured to be input to the DPD.
8. The system of claim 7 , further comprising a bandpass filter configured to filter the power amplifier output signal.
9. The system of claim 8 , wherein the bandpass filter has a filter bandwidth less than the DPD bandwidth.
10. The system of claim 7 , further comprising a down-converter configured to down-convert the power amplifier output signal.
11. The system of claim 7 , wherein the digital-to-analog converter has a sampling rate less than twice the DPD bandwidth.
12. A communications system comprising:
a digital predistorter (DPD) configured to generate a DPD output signal based on an input signal, the DPD initially using a set of first DPD coefficients, wherein the DPD has a DPD bandwidth;
a digital-to-analog converter having a first bandwidth, the digital-to-analog converter configured to sample the DPD output signal to produce an analog signal;
a modulator configured to modulate the analog signal;
a power amplifier configured to amplify the modulated analog signal to produce a power amplifier output signal;
a duplexer configured to filter the power amplifier output signal to produce a filtered signal, wherein the duplexer has a duplexer bandwidth less than the first bandwidth;
an antenna configured to transmit the filtered signal; and
feedback components having a second bandwidth less than the first bandwidth, the feedback components configured to sample the power amplifier output signal to produce a digital signal,
wherein the digital signal includes a next set of DPD coefficients.
13. The system of claim 12 , further comprising an up-converter configured to up-convert the modulated signal.
14. The system of claim 12 , further comprising a bandpass filter configured to filter the power amplifier output signal.
15. The system of claim 14 , wherein the bandpass filter has a filter bandwidth less than the DPD bandwidth.
16. The system of claim 12 , further comprising a down-converter configured to down-convert the power amplifier output signal.
17. The system of claim 12 , wherein the digital-to-analog converter has a sampling rate less than twice the DPD bandwidth.