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US 8,478,210 B2Granted
Apparatus and method of digital predistortion for power amplifiers with dynamic nonlinearities
AssigneeTexas Instruments Incorporated
InventorsHardik P. Gandhi, Lei Ding
Life of this patent
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Abstract
Power amplifiers (PAs) using a Doherty or other power output level sensitive configuration have been employed for several years in telecommunications (as well as other applications) to take advantage of efficiency gains. For many of these applications, baseband signals are predistorted to compensate for nonlinearities in the PAs, but because there is a “switching event” in a Doherty-type amplifier (for example), the nonlinearities become dynamically varying. As a result, digital predistortion (DPD) becomes increasingly difficult to perform. Here, DPD modules are provided that adapt to changes in dynamically varying PAs based on a determination of the average power or other relevant metric prior to transmission.
Claims12
An apparatus comprising:
- baseband circuitry that receives a baseband signal, wherein the baseband circuitry includes a operational mode circuitry to determine an operation mode metric for the baseband signal;
- and
- a digital predistortion (DPD) module that receives an output from the baseband circuitry and to receive the operational mode metric,
- wherein the DPD module selects one of a plurality of predistortions based at least in part on the operational mode metric, and
- wherein the DPD module applies a selected predistortion to the output from the baseband circuitry so as to predistort the output from the baseband circuitry to compensate for nonlinearities in a power amplifier having a plurality of operating modes, and
- wherein the selected predistotion is associated with at least one of the operating modes of the power amplifier that corresponds to the operational mode metric,
- wherein the baseband circuitry further comprises:
- input circuitry that receives the baseband signal;
- and
- a crest factor reduction (CFR) module that receives an output from the input circuitry that provides the output from the baseband circuitry to the DPD module,
- wherein the DPD module further comprises a controller that receives the output from the baseband circuitry, wherein the controller includes:
- a lookup table (LUT) that stores the plurality of predistortions;
- and
- an equalizer,
- wherein the operational mode circuitry further comprises a power meter, and wherein the operational mode metric further comprises output power, and wherein the DPD module further comprises:
- a plurality of comparators, wherein each comparator of the plurality of comparators receives at least one of a plurality of thresholds, and wherein each comparator receives the output power, and wherein each comparator generates a bit of a selection signal T1-n;
- a solutions table that generates a polynomial solution based at least in part on the T1-n selection signal;
- and
- a converter that generate an LUT selection based at least in part on the polynomial solution for the controller.
16 more elements
An apparatus comprising:
- a transmit processor having:
- baseband circuitry that receives a baseband signal, wherein the baseband circuitry includes a operational mode circuitry to determine an operational mode metric for the baseband signal;
- a DPD module that receives an output from the baseband circuitry and to receive the operational mode metric, wherein the DPD module selects one of a plurality of predistortions based at least in part on the operational mode metric, and wherein the DPD module applies a selected predistortion to the output from the baseband circuitry so as to predistort the output from the baseband circuitry to compensate for nonlinearities in a power amplifier having a plurality of operating modes, and wherein the selected predistotion is associated with at least one of the operating modes of the power amplifier that corresponds to the operational mode metric;
- a transmit interface that receives an output from the DPD module;
- and
- a feedback interface that provides feedback to the DPD module;
- a transmit circuit that is coupled to the transmit interface;
- and
- a feedback circuit that is coupled to the feedback interface,
- wherein the baseband circuitry further comprises:
- input circuitry that receives the baseband signal;
- and
- a CFR module that receives an output from the input circuitry that provides the output from the baseband circuitry to the DPD module,
- wherein the DPD module further comprises a controller that receives the output from the baseband circuitry, wherein the controller includes:
- an LUT that stores the plurality of predistortions;
- and
- an equalizer,
- wherein the operational mode circuitry further comprises a power meter, and wherein the operational mode metric further comprises output power, and
- wherein the DPD module further comprises:
- a plurality of comparators, wherein each comparator of the plurality of comparators receives at least one of a plurality of thresholds, and wherein each comparator receives the output power, and wherein each comparator generates a bit of a selection signal T1-n;
- a solutions table that generates a polynomial solution based at least in part on the T1-n selection signal;
- and
- a converter that generate an LUT selection based at least in part on the polynomial solution for the controller.
20 more elements
A method comprising:
- determining a output power for a baseband signal;
- selecting at least one of a plurality of predistortions based at least in part on the output power, wherein the selected predistotion is associated with at least one of a plurality of operating modes of a power amplifier corresponding to the output power;
- predistorting the baseband signal with the selected predistortion so as to compensate for nonlinearities in the power amplifier at the output power and to generate a predistorted signal;
- converting the predistorted signal into an analog signal;
- modulating the analog signal to generate a radio frequency (RF) signal;
- and
- amplifying the RF signal with the power amplifier,
- wherein the step of selecting and predistorting further comprises:
- receiving the baseband signal by a plurality of DPD modules;
- combining outputs from each of the DPD modules based on the output power to generate the predistorted signal,
- processing the baseband signal with a CFR process prior to the step of selecting, wherein the DPD module further comprises:
- a plurality of comparators, wherein each comparator of the plurality of comparators receives at least one of a plurality of thresholds, and wherein each comparator receives the output power, and wherein each comparator generates a bit of a selection signal T1-n;
- a solutions table that generates a polynomial solution based at least in part on the T1-n selection signal;
- and
- a converter that generate an LUT selection based at least in part on the polynomial solution for the controller.
12 more elements
Dependencies are inferred from the claim text.