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 non-transitory computer readable information storage media having instructions stored thereon, that when executed by one or more processors, cause to be performed a method of operating a communications system 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 media of claim 1 , further comprising up-converting the modulated signal.
3. The media of claim 1 , further comprising filtering the amplified signal using a bandpass filter.
4. The media of claim 3 , wherein the bandpass filter has a filter bandwidth less than the DPD bandwidth.
5. The media of claim 1 , further comprising downconverting the amplified signal.
6. The media 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 non-transitory computer readable information storage media having instructions stored thereon, that when executed by one or more processors, cause to be performed a method of operating a communications system comprising:
receiving a signal at a digital predistorter (DPD) characterized by a DPD bandwidth;
introducing predistortion to the signal using the DPD;
filtering the predistorted signal using a digital filter characterized by a filter bandwidth less than the DPD bandwidth;
converting the filtered signal to an analog signal;
modulating the analog signal;
amplifying the modulated signal;
coupling a portion of the amplified signal to provide a feedback signal;
filtering the feedback signal using a band-pass filter;
downconverting the filtered feedback signal;
converting the downconverted signal to a digital signal; and
providing the digital signal to the DPD.
8. The media of claim 7 , wherein the band-pass filter comprises at least one of a radio frequency (RF) filter or an intermediate frequency (IF) filter.
9. The media of claim 7 , wherein the filter bandwidth is between 30 MHz and 50 MHz.
10. The media of claim 9 , wherein filtering the feedback signal using a band-pass filter is performed over a band-pass bandwidth less than the DPD bandwidth.
11. The media of claim 10 , wherein the band-pass bandwidth is between 30 MHz and 50 MHz.
12. The media of claim 7 , wherein converting the downconverted signal is performed at a sampling rate value less than twice the value of the DPD bandwidth.
13. The media of claim 12 , wherein the sampling rate is between 60 Msps and 100 Msps.