Predistortion of amplifier input signals
View Patent ↗Described herein are devices, methods, and techniques related to predistortion of amplifier signals based on an operating condition. Predistortion techniques are described that mitigate or eliminate the effects of variable operating conditions, including nonlinear effects, on amplified signals. Nonlinearities may be mitigated by compensating at a baseband signal prior to amplification, generally using scaling and a static characteristic that is valid for a broad range of operating conditions.
1. A method comprising:
performing predistortion on a baseband signal using a static characteristic under a first operating condition to produce a predistorted baseband signal;
determining a second operating condition;
comparing the first operating condition to the second operating condition; and
modifying a property of the predistorted baseband signal based on the static characteristic and the comparison of the first operating condition to the second operating condition by scaling a linear gain component and/or a nonlinear component of the baseband signal,
wherein comparing the first operating condition to the second operating condition results in determining a difference in one or more of the following: temperature, supply voltage, operating frequency, load condition, or bias setting;
determining an operating condition characteristic based on the comparison of the first operating condition to the second operating condition;
determining a single static nonlinear function that represents the operating condition characteristic;
scaling the single static nonlinear function by a constant based on the comparison of the first operating condition to the second operating condition; and
modifying the property of the predistorted baseband signal based on the scaled single static nonlinear function.
2. The method of claim 1 , further comprising performing predistortion on a magnitude component and/or a phase component of the baseband signal.
3. The method of claim 2 , further comprising scaling the magnitude component and/or the phase component of the baseband signal.
4. The method of claim 2 , further comprising modifying the magnitude component and/or the phase component of the baseband signal based on a value listed in a look up table, wherein the value is addressed in the lookup table based on the static characteristic.
5. The method of claim 1 , further comprising modifying the property of the predistorted baseband signal based on a value listed in a look up table, wherein the value is addressed in the lookup table based on a feedback signal comprising a modulated output signal.