Method and apparatus for microwave predistorter linearizer with electronic tuning

DETAILED DESCRIPTION In one aspect of the invention, a predistorter linearizer for use with a radio frequency amplifier comprises a gain distorter having a first variable load to provide variability in the gain characteristic of the gain distorter.
The predistorter linearizer also includes a phase distorter having a second variable load to provide variability in a phase characteristic of the phase distorter.
The gain distorter and phase distorter cooperate to modify a signal prior to its input to the radio frequency amplifier.
In another aspect of the present invention, an apparatus includes a first circuit having an input terminal and an output terminal.
The first circuit includes three branches connected in electrical parallel between the input and output terminals.
The first branch has a nonlinear element, such as a diode or field-effect transistor (FET), and a variable load in series, and the second branch has a nonlinear element and a variable load.
The third branch has a variable load.
A second circuit is connected to the first circuit and also includes three branches connected in electrical parallel.
In the second circuit, the first branch includes a nonlinear element and a variable load, and the second branch also has a nonlinear element and a variable load.
The third branch in the second circuit comprises a variable load.
The first and second circuits are coupled in electrical series.
In yet another aspect of the invention, a method is provided for modifying a signal for later amplification, the method comprising adjusting a circuit to provide a desired magnitude characteristic and adjusting the circuit to provide a desired phase characteristic.
The signal to be modified is received and modified using the desired magnitude and phase characteristics to produce a distorted signal.
The distorted signal is provided to an amplifier for amplification, wherein the modification of the signal is offset by a further modification in the amplifier, resulting in a linearized amplifier output