Modulation agnostic digital hybrid mode power amplifier system and method
A RF-digital hybrid mode power amplifier system for achieving high efficiency and high linearity in wideband communication systems is disclosed. The present invention is based on the method of adaptive digital predistortion to linearize a power amplifier in the RF domain. The present disclosure enables a power amplifier system to be field reconfigurable and support multi-modulation schemes (modulation agnostic), multi-carriers and multi-channels. As a result, the digital hybrid mode power amplifier system is particularly suitable for wireless transmission systems, such as base-stations, repeaters, and indoor signal coverage systems, where baseband I-Q signal information is not readily available.
1. A digital predistortion system for linearizing the output of power amplifiers comprising:
input signal suitable for wireless communications,
at least one power amplifier for outputting an amplified signal,
at least one feedback signal derived from the amplified signal including a representation of a noise characteristic of the at least one power amplifier, estimator logic responsive to the at least one feedback signal for generating predistortion coefficients based at least in part on feedback path delay determined from the correlation given by the equation
C
(
m
)
=
∑
i
=
0
N
-
1
sign
(
x
(
i
+
1
)
-
x
(
i
)
)
sign
(
y
(
i
+
m
+
1
)
-
y
(
i
+
m
)
)
n
(
delay
)
=
Max
(
C
(
m
)
)
where x(n) represents transmission data, y(n) represents feedback data, c(m) is a correlation function, N is a number of data per block, m is a variable representing time, I is a counter for summation, and n(delay) is a delay time.
2. The digital predistortion system of claim 1 configured for base station applications further comprising a digital field programmable gate array that includes one or more of a digital up-converter, a crest factor reduction, a predistorter, or a digital quadrature modulator.
3. The digital predistortion system of claim 1 configured for repeater applications further comprising a digital field programmable gate array that includes at least one of a digital quadrature demodulator, a crest factor reduction, a predistorter, or a digital quadrature modulator.
4. The digital predistortion system of claim 1 further comprising a digital field programmable gate array that provides predistortion that compensates adaptively for both nonlinearity and memory effects by generating asymmetric distortion of the power amplifier.
5. The digital predistortion system of claim 1 further comprising a digital field programmable gate array that includes an adaptation algorithm to determine the optimum gate bias voltage of the power amplifier for stabilizing the linearity fluctuations due to the temperature changes of the power amplifier.
6. The digital predistortion system of claim 1 wherein the power amplifier portion uses at least one of the following efficiency boosting techniques: Doherty, Envelope Elimination and Restoration, Envelope Tracking, Envelope Following, or Linear amplification using Nonlinear Components in order to maximize the efficiency of the power amplifier system.