RF power amplifier linearization

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, schematically depicted in FIG.
1 is an amplifier linearization system constructed in accordance with, and embodying, the principles of the present invention.
This system 2 generally comprises: (a) a difference determining circuit 4; (b) a bandpass filter 5, (c) an amplifier circuit 6; (c) a phase correction circuit 8; and (d) a phase correction amount determining circuit 9.
The system 2 depicted in FIG.
1 operates in the following basic manner.
Initially, an input signal is introduced into the difference determining circuit 4.
The difference determining circuit 4 generates an output signal that is filtered by the bandpass filter 5 and introduced into the amplifier circuit 6.
The amplifier circuit 6 generates an amplified output signal corresponding to the filtered output signal.
A feedback signal is derived from the amplified output signal.
The phase correction circuit 8 shifts the phase of this feedback signal to generate a phase-shifted feedback signal.
The phase correction amount determining circuit 9 determines the amount of phase correction required for the frequency at which the system 2 is operating.
This phase-shifted feedback signal is introduced into the difference determining circuit 4.
The output signal generated by this circuit 4 is the difference between the input signal and the phase-shifted feedback signal.
For the system 2 to remain stable, the phase of the fed back signal must be properly adjusted to achieve reduced distortion over the range of frequencies of the amplifier.
Without the phase correction circuit 8 and phase correction amount circuit 9, the phase of the fed back signal will not be properly adjusted because the bandpass filter 5 and the amplifier circuit 6 cause relatively severe phase shift in the output signal.
More particularly, the phase of the phase-shifted feedback signal should be at or relatively near an integer multiple of 360 degrees relative to (i.
e.
, in phase with) the input signal phase so that negative feedback will be obtained as a result of signal subtraction performed by the difference determining circuit 4