Predistortion for hybrid digital/analog precoders
A 5G base station transmitter at least partially precodes data for beam forming, and generates digital precoded baseband signals. Cross product circuitry coupled to the digital precoder, generates digital cross products of the digital precoded baseband signals. Both the baseband signals and the cross products are put through digital-to-analog converters (DACs), then provided to an analog non-linear precoder. The analog non-linear precoder combines the analog baseband signals, the cross products, with pre-distortion and precoder coefficients to generate a signal that is pre-compensated for power amplifier non-linearity. The pre-compensated signal is amplified by the power amplifier and transmitted via a phased antenna array. The number of extra DACs required for inserting pre-distortion when a hybrid digital/analog precoder is used can be limited to approximately N RF ( N RF - 1 ) 2 , where N RF is the number of outputs of the digital precoder. This is significantly fewer than the number of extra DACs used by other methods.
1. A system comprising:
a cross product generator operable to produce a plurality of cross products according to a plurality of data signals, wherein each cross product of the plurality of cross products is associated with a respective pair of data signals in the plurality of data signals; and
a precoder operable to produce one or more pre-compensated signals according to the plurality of data signals and the plurality of cross products, wherein each pre-compensated signal of the one or more pre-compensated signals is associated with a plurality of coefficients, and wherein each coefficients of the plurality of coefficients is associated with a respective data signal of the plurality of data signals, and wherein the precoder is in an analog precoder portion of an integrated circuit.
2. The system of claim 1 , wherein the system comprises a plurality of digital-to-analog converters operable to the convert the plurality of data signals from digital to analog.
3. The system of claim 1 , wherein the cross product generator comprises a plurality of complex multipliers associated with the plurality of cross-products.
4. The system of claim 1 , wherein the plurality of coefficients associated with each pre-compensated signal of the one or more pre-compensated signals comprises a plurality of precoder coefficients.
5. The system of claim 4 , wherein the plurality of precoder coefficients is produced in a digital integrated circuit.
6. The system of claim 1 , wherein each pre-compensated signal of the one or more pre-compensated signals is associated with an adaptive pre-distortion coefficient generated according to feedback from one or more RF power amplifiers.
7. The system of claim 1 , wherein the system is embedded in an integrated circuit.
8. The system of claim 7 , wherein the integrated circuit is a basestation transmitter.
9. The system of claim 1 , wherein the cross product generator is in a digital portion of an integrated circuit.
10. A method comprising:
producing, in a cross product generator, a plurality of cross products according to a plurality of data signals, wherein each cross product of the plurality of cross products is associated with a respective pair of data signals in the plurality of data signals; and
produce, in a precoder, one or more pre-compensated signals according to the plurality of data signals and the plurality of cross products, wherein each pre-compensated signal of the one or more pre-compensated signals is associated with a plurality of coefficients, and wherein each coefficients of the plurality of coefficients is associated with a respective data signal of the plurality of data signals, and wherein the precoder is in an analog precoder portion of an integrated circuit.
11. The method of claim 10 , wherein the method comprises converting the plurality of data signals from digital to analog using a plurality of digital-to-analog converters.
12. The method of claim 10 , wherein the cross product generator comprises a plurality of complex multipliers associated with the plurality of cross-products.
13. The method of claim 10 , wherein the plurality of coefficients associated with each pre-compensated signal of the one or more pre-compensated signals comprises a plurality of precoder coefficients.
14. The method of claim 13 , wherein the method comprises producing the plurality of precoder coefficients in a digital integrated circuit.
15. The method of claim 10 , wherein the method comprises generating one or more adaptive pre-distortion coefficients according to feedback from one or more RF power amplifiers, wherein each pre-compensated signal of the one or more pre-compensated signals is associated with an adaptive pre-distortion coefficient of the one or more adaptive pre-distortion coefficients.
16. The method of claim 10 , wherein the method is performed in an integrated circuit.
17. The method of claim 16 , wherein the integrated circuit is a basestation transmitter.
18. The method of claim 10 , wherein the cross product generator is in a digital portion of an integrated circuit.