Digital pre-distorter
A digital pre-distorter (DPD) for an RF transceiver system having multiple antennas includes a DPD controller, first and second address generators, stream select and antenna select muxes, first and second lookup tables (LUTs), first and second dynamic routing logic units, multipliers, an adder, and an accumulator. The DPD controller generates antenna select, stream select and stream routing signals indicative of selection of antennas, the first and second LUTs, and input signals. The DPD controller configures the DPD to share the multipliers and the first and second LUTs between multiple antennas by providing the antenna select signal to the antenna select mux, the stream select signal to the stream select mux, and the stream routing signals to the first and second dynamic routing logic units.
1. A digital pre-distorter (DPD) for pre-distorting a plurality of input signals corresponding to a plurality of antennas, comprising:
a DPD controller for storing (i) an antenna select value indicative of a count of selected antennas of the plurality of antennas, and (ii) a stream select value indicative of a selection of the plurality of input signals, and generating an antenna select signal based on the antenna select value, and stream select and stream routing signals based on the stream select value;
a first address generator for receiving a first input signal of the plurality of input signals corresponding to a first antenna, and generating a first set of addresses;
a second address generator for receiving a second input signal of the plurality of input signals corresponding to a second antenna, and generating a second set of addresses;
a stream select multiplexer having (i) first and second input terminals connected to the first and second address generators for receiving the first and second sets of addresses, respectively, (ii) a select terminal connected to the DPD controller for receiving the stream select signal, and (iii) an output terminal for outputting an intermediate set of addresses;
a first set of lookup tables corresponding to the first antenna for storing a plurality of coefficients, wherein the first set of lookup tables is connected to the first address generator for receiving the first set of addresses, and outputting a first set of coefficients of the plurality of coefficients;
a second set of lookup tables corresponding to the second antenna for storing the plurality of coefficients, wherein the second set of lookup tables is connected to the output terminal of the stream select multiplexer for receiving the intermediate set of addresses, and outputting a second set of coefficients of the plurality of coefficients;
a first dynamic routing logic unit connected to the first and second sets of lookup tables for receiving the first and second sets of coefficients, respectively, and to the DPD controller for receiving the stream routing signal, and outputting a selected set of coefficients;
an antenna select multiplexer having (i) first and second input terminals for receiving the first and second input signals, respectively, (ii) a select terminal connected to the DPD controller for receiving the antenna select signal, and (iii) an output terminal for outputting a selected input signal;
a plurality of multipliers, connected to the first dynamic routing logic unit and the antenna select multiplexer, for receiving the selected set of coefficients and the selected input signal, respectively, and generating a plurality of pre-distorted samples;
an adder connected to the plurality of multipliers for receiving and adding the plurality of pre-distorted samples and generating a pre-distorted signal;
an accumulator connected to the adder for receiving the pre-distorted signal and generating an accumulated pre-distorted signal; and
a second dynamic routing logic unit, connected to the adder, the accumulator and the DPD controller, for receiving at least one of the pre-distorted and accumulated pre-distorted signals and the stream routing signal, and outputting at least one of first and second pre-distorted output signals corresponding to the first and second antennas, respectively.
2. The DPD of claim 1 , wherein the DPD controller, the first and second address generators, the first and second sets of lookup tables, the first and second dynamic routing logic units, and the stream and antenna select multiplexers operate at a first sampling rate, and the plurality of multipliers operate at a second sampling rate.
3. The DPD of claim 2 , wherein the DPD controller generates the stream select signal at a first logic state indicative of the selection of the second input signal, toggles the stream routing signal between logic low and logic high states indicative of selection of the first and second sets of lookup tables, respectively, and toggles the antenna select signal between logic low and logic high states indicative of selection of the first antenna for transmission of a first radio-frequency (RF) signal generated based on the first pre-distorted output signal and the second antenna for transmission of a second RF signal generated based on the second pre-distorted output signal, respectively, and wherein the DPD controller toggles the stream routing and antenna select signals at the second sampling rate.
4. The DPD of claim 3 , wherein the plurality of multipliers receive the selected input signal indicative of the first and second input signals sampled at the second sampling rate and the selected set of coefficients that includes the first and second sets of coefficients, and multiplies the first and second sets of coefficients with the first and second input signals, respectively, wherein the DPD uses the plurality of multipliers for generating the plurality of pre-distorted samples for the first and second antennas.
5. The DPD of claim 4 , wherein the second dynamic routing logic unit outputs the pre-distorted signal as the first and second pre-distorted output signals corresponding to the first and second antennas, respectively, based on the stream select signal.
6. The DPD of claim 2 , wherein the DPD controller generates the stream select signal at a logic low state indicative of the selection of the first input signal, toggles the stream routing signal between logic low and logic high states at the second sampling rate indicative of selection of the first and second sets of lookup tables, respectively, and generates the antenna select signal at a logic low state indicative of selection of the first antenna for transmission of a first radio-frequency (RF) signal generated based on the first pre-distorted output signal.
7. The DPD of claim 6 , wherein:
the plurality of multipliers receive the selected input signal indicative of the first input signal sampled at the first sampling rate and the selected set of coefficients that includes the first and second sets of coefficients, and
multiplies the selected set of coefficients with the first input signal, and
wherein the DPD uses the plurality of multipliers for generating the plurality of pre-distorted samples based on the first and second sets of coefficients for the first antenna.
8. The DPD of claim 7 , wherein the accumulator generates the accumulated pre-distorted signal that includes the plurality of pre-distorted samples generated based on the first and second sets of coefficients and the first input signal.
9. The DPD of claim 8 , wherein the second dynamic routing logic unit outputs the accumulated pre-distorted signal as the first pre-distorted output signal corresponding to the first antenna based on the logic low stream select signal.
10. The DPD of claim 1 , wherein the first and second dynamic routing logic units include multiplexing and de-multiplexing units.
11. A radio-frequency (RF) transceiver for generating a plurality of RF signals based on a corresponding plurality of input signals, wherein the RF signals are transmitted by way of a corresponding plurality of antennas, the RF transceiver comprising:
a digital pre-distorter (DPD) for pre-distorting the plurality of input signals, the DPD comprising:
a DPD controller for (i) storing an antenna select value indicative of a count of selected antennas of the plurality of antennas and a stream select value indicative of a selection of the plurality of input signals, (ii) generating an antenna select signal based on the antenna select value and stream select and (iii) stream routing signals based on the stream select value;
a first address generator for receiving a first input signal of the plurality of input signals corresponding to a first antenna and generating a first set of addresses;
a second address generator for receiving a second input signal of the plurality of input signals corresponding to a second antenna and generating a second set of addresses;
a stream select multiplexer having (i) first and second input terminals connected to the first and second address generators for receiving the first and second sets of addresses, respectively, (ii) a select terminal connected to the DPD controller for receiving the stream select signal, and (iii) an output terminal for outputting an intermediate set of addresses;
a first set of lookup tables corresponding to the first antenna for storing a plurality of coefficients, wherein the first set of lookup tables is connected to the first address generator for receiving the first set of addresses and outputting a first set of coefficients of the plurality of coefficients;
a second set of lookup tables corresponding to the second antenna for storing the plurality of coefficients, wherein the second set of lookup tables is connected to the output terminal of the stream select multiplexer for receiving the intermediate set of addresses and outputting a second set of coefficients of the plurality of coefficients;
a first dynamic routing logic unit connected to the first and second sets of lookup tables for receiving the first and second sets of coefficients, respectively, and to the DPD controller for receiving the stream routing signal and outputting a selected set of coefficients;
an antenna select multiplexer having (i) first and second input terminals for receiving the first and second input signals, respectively, (ii) a select terminal connected to the DPD controller for receiving the antenna select signal, and (iii) an output terminal for outputting a selected input signal;
a plurality of multipliers, connected to the first dynamic routing logic unit and the antenna select multiplexer, for receiving the selected set of coefficients and the selected input signal, respectively, and generating a plurality of pre-distorted samples;
an adder, connected to the plurality of multipliers, for receiving and adding the plurality of pre-distorted samples and generating a pre-distorted signal;
an accumulator connected to the adder for receiving the pre-distorted signal and generating an accumulated pre-distorted signal; and
a second dynamic routing logic unit connected to the adder, the accumulator and the DPD controller, for receiving at least one of the pre-distorted and accumulated pre-distorted signals and the stream routing signal, and outputting at least one of first and second pre-distorted output signals corresponding to the first and second antennas, respectively; and
a radio-frequency integrated circuit (RFIC) that receives at least one of the first and second pre-distorted output signals and generates first and second RF signals, the RFIC comprising:
a first digital-to-analog converter (DAC) connected to the second dynamic routing logic unit for receiving the first pre-distorted output signal and generating a first analog RF signal;
a second DAC connected to the second dynamic routing logic unit for receiving the second pre-distorted output signal and generating a second analog RF signal;
a first power amplifier connected to the first DAC for receiving the first analog RF signal, and generating and providing the first RF signal to the first antenna; and
a second power amplifier connected to the second DAC for receiving the second analog RF signal, and generating and providing the second RF signal to the second antenna.
12. The RF transceiver of claim 11 , wherein the DPD controller, the first and second address generators, the first and second sets of lookup tables, the first and second dynamic routing logic units, and the stream and antenna select multiplexers operate at a first sampling rate and the plurality of multipliers operate at a second sampling rate.
13. The RF transceiver of claim 12 , wherein the DPD controller generates the stream select signal at a logic high state indicative of the selection of the second input signal, toggles the stream routing signal to select one of the first and second sets of lookup tables, respectively, and toggles the antenna select signal to select the first antenna for transmission of the first RF signal and the second antenna for transmission of the second RF signal, respectively, and wherein the DPD controller toggles the stream routing and antenna select signals at the second sampling rate.
14. The RF transceiver of claim 13 , wherein the multipliers receive the selected input signal indicative of the first and second input signals sampled at the second sampling rate and the selected set of coefficients that includes the first and second sets of coefficients, and multiplies the first and second sets of coefficients with the first and second input signals, respectively, wherein the DPD uses the multipliers for generating the plurality of pre-distorted samples for the first and second antennas.
15. The RF transceiver of claim 14 , wherein the second dynamic routing logic unit outputs the pre-distorted signal as the first and second pre-distorted output signals corresponding to the first and second antennas, respectively, based on the stream select signal.
16. The RF transceiver of claim 12 , wherein the DPD controller generates the stream select signal at a logic low state indicative of the selection of the first input signal, toggles the stream routing signal between logic low and logic high states at the second sampling rate indicative of selection of the first and second sets of lookup tables, respectively, and generates the antenna select signal at a logic low state indicative of selection of the first antenna for transmission of the first RF signal.
17. The RF transceiver of claim 16 , wherein the multipliers receive the selected input signal indicative of the first input signal sampled at the first sampling rate and the selected set of coefficients that includes the first and second sets of coefficients, and multiply the selected set of coefficients with the first input signal, and wherein the DPD uses the multipliers for generating the plurality of pre-distorted samples based on the first and second sets of coefficients for the first antenna.
18. The RF transceiver of claim 17 , wherein the accumulator generates the accumulated pre-distorted signal that includes the plurality of pre-distorted samples generated based on the first and second sets of coefficients and the first input signal.
19. The RF transceiver of claim 18 , wherein the second dynamic routing logic unit outputs the accumulated pre-distorted signal as the first pre-distorted output signal corresponding to the first antenna based on the logic low stream select signal.
20. The RF transceiver of claim 11 , wherein the first and second dynamic routing logic units include multiplexing and de-multiplexing units.