Apparatus for removing distortions created by an amplifier

1. A power amplifier, comprising:

a non-linear low power pre-distortion amplifier for transforming a carrier signal to a pre-distorted signal having a carrier component with out-of phase non-linear distortions wherein the non-linear low power pre-distortion amplifier comprises:

a first delay element for generating a first delayed carrier signal;

a first attenuator coupled to the first delay element for generating an attenuated carrier signal;

a first phase shifter coupled to the carrier signal for generating a phase- shifted carrier signal from the attenuated carrier signal;

a first detector for controlling gain and phase of the first attenuator and the first phase shifter, respectively, according to desired characteristics of the phase shifted carrier signal;

a first temperature and aging control adjuster coupled ot the first phase shifter for generating a phase bias signal that adjusts variations in phase as a function of temperature and aging

a non-linear low power amplifier for generating from the carrier signal an amplified carrier component with non-linear distortions;

a second attenuator coupled to the non-linear low power amplifier for generating an attenuated amplified carrier component with attenuated non-linear distortions;

a second phase shifter coupled to the second attenuator for generating a phase-shifted signal having an out-of-phase attenuated carrier component with out-of phase attenuated non-linear distortions; and

a second delay element for generating a second delayed carrier signal;

a first combining point for combining the phase-shifted signal and the carrier signal, thereby generating a distortion signal having the out-of phase attenuated non-linear distortions, wherein the distortion signal generated from the combining the phase-shifted signal with the second delayed carrier signal;

a second detector for controlling gain and phase of the second attenuator and the second phase shifter, respectively, according ot characteristics desired in the distortion signal;

a second temperature and aging control adjuster coupled to the first attenuator for generating a bias signal that adjusts variations in gain as a function of temperature and aging, and

a second combining point for generating the pre-distorted signal by combining the phase-shifted carrier signal and the distortion signal; and

a non-linear power amplifier having non-linear characteristics similar to a portion of the non-linear low power pre-distortion amplifier for generating from the pre-distorted signal a transmission signal having an amplified carrier component with substantially diminished non-linear distortions.

2. The power amplifier of claim 1 , wherein the non-linear power amplifier comprises a plurality of parallel non-linear power amplifiers.

3. The power amplifier of claim 1 , further comprising a delay element for generating a delayed carrier signal, wherein the first combining point generates the distortion signal from combining the phase-shifted signal with the delayed carrier signal.

4. The power amplifier of claim 1 , wherein the first and second temperature and aging control adjusters are selected from one among a group of circuits comprising a thermistor circuit, a processor coupled to a digital-to-analog converter (DAC) and a temperature and aging sensor for controlling operations thereof, and an amplitude modulation (AM) detector, each of said circuits generates one or more bias signals characterized to track temperature and aging variations of the non-linear power amplifier.

5. The power amplifier of claim 1 , wherein the AM detector comprises:

an AM modulator for injecting into the transmission signal an AM tone;

an AM detector for detecting AM signals embedded in the transmission signal;

a first bandbpass filter for isolating a desired AM tone from the AM signals;

a second bandpass filter generates from the AM tone a filtered AM tone; and

a correlator coupled to the first and second bandpass filters for generating a signal corresponding to the amplitude of the detected AM tone.

6. A base station, comprising:

a receiver for receiving signals from a selective call radio (SCR);

a transmitter for generating a transmission signal directed to the SCR; and

a processor for controlling operations of the receiver and the transmitter, wherein the transmitter comprises:

an up-converter for transforming a signal at a first operating frequency to a carrier signal;

a non-linear low power pre-distortion amplifier for transforming the carrier signal to a pre-distorted signal having a carrier component with out-of-phase non-linear distortions wherein the non-linear low power pre-distortion amplifier comprises:

a first delay element for generating a first delayed carrier signal;

a first attenuator coupled to the first delay element for generating an attenuated carrier signal;

a first phase shifter coupled to the carrier signal for generating a phase-shifted carrier signal from the attenuated carrier signal;

a first detector for controlling gain and phase of the first attenuator and the first phase shifter, respectively, according to desired characteristics of the phase shifted carrier signal;

a first temperature and aging control adjuster coupled ot the first phase shifter for generating a phase bias signal that adjusts variations in phase as a function of temperature and aging

a non-linear low power amplifier for generating from the carrier signal an amplified carrier component with non-linear distortions;

a second attenuator coupled to the non-linear low power amplifier for generating an attenuated amplified carrier component with attenuated non-linear distortions;

a second phase shifter coupled to the second attenuator for generating a phase-shifted signal having an out-of-phase attenuated carrier component with out-of-phase attenuated non-linear distortions; and

a second delay element for generating a second delayed carrier signal;

a first combining point for combining the phase-shifted signal and the carrier signal, thereby generating a distortion signal having the out-of-phase attenuated non-linear distortions, wherein the distortion signal generated from the combining the phase-shifted signal with the second delayed carrier signal;

a second detector for controlling gain and phase of the second attenuator and the second phase shifter, respectively, according ot characteristics desired in the distortion signal;

a second temperature and aging control adjuster coupled to the first attenuator for generating a bias signal that adjusts variations in gain as a function of temperature and aging, and

a second combining point for generating the pre-distorted signal by combining the phase-shifted carrier signal and the distortion signal; and

a non-linear power amplifier having non-linear characteristics similar to a portion of the non-linear low power pre-distortion amplifier for generating from the pre-distorted signal a transmission signal for radiating from an antenna, wherein the transmission signal has an amplified carrier component with substantially diminished non-linear distortions.

7. The base station of claim 6 wherein the first and second temperature and aging control adjusters are selected from one among a group of circuits comprising a thermistor circuit, the processor coupled to a digital-to-analog converter (DAC) and a temperature and aging sensor for controlling operations thereof, and an amplitude modulation (AM) detector, each of said circuits generates one or more bias signals characterized to track temperature and aging variations of the non-linear power amplifier.

8. The base station of claim 6 , wherein the non-linear power amplifier comprises a plurality of parallel non-linear power amplifiers.