Method and apparatus for reducing distortion in a high efficiency power amplifier
AssigneeMotorola, Inc.
InventorChristopher David Grondahl
Life of this patent
Estimating the term…
Abstract
A method and apparatus for efficient power amplification of a wideband signal with a correspondingly wide modulation bandwidth includes an envelope detector (220), an envelope amplifier (270), a driver amplifier (250), and a power amplifier (260). The driver amplifier (250) includes a dual gate variable gain amplifier (252) that has a substantially constant phase characteristic over a wide dynamic range. The power amplifier (260) is modulated by an amplified envelope signal from the envelope amplifier (270), and is driven by an output of the driver amplifier (250). The operation of the cascaded driver amplifier (250) and power amplifier (260) allow the power amplifier (260) to operate a substantially constant compression point, and reduced distortion.
Claims15
A method of reducing distortion in a power amplifier, said method comprising the steps of:
- envelope detecting an input signal to produce an envelope signal;
- producing a pulsewidth modulated signal with a duty cycle proportional to an amplitude of said envelope signal;
- filtering said pulsewidth modulated signal to produce an amplified envelope signal;
- sampling said amplified envelope signal to produce a digital envelope signal;
- amplifying said input signal with a dual gate variable gain amplifier wherein a gain of said dual gate variable gain amplifier is controlled by said digital envelope signal;
- and
- further amplifying said input signal with a power amplifier stage wherein said power amplifier stage is modulated by said amplified envelope signal.
A power amplifier with reduced phase distortion, said power amplifier comprising:
- a driver amplifier stage having an input coupled to an input of said power amplifier, said driver amplifier stage being comprised of a dual gate variable gain amplifier;
- an envelope detector for detecting an envelope of an input signal to produce an envelope signal;
- an envelope amplifier coupled to said envelope detector, for producing an amplified envelope signal;
- an analog to digital converter, responsive to said envelope signal, for controlling a gain of said dual gate variable gain amplifier;
- and
- a power amplifier stage having an input coupled to an output of said driver amplifier stage, and having an output coupled to an output of said power amplifier, wherein said power amplifier stage is modulated by said amplified envelope signal.
A power amplifier circuit comprising:
- means for creating an envelope signal from an input signal;
- a dual gate variable gain amplifier for amplifying said input signal;
- means, responsive to said envelope signal, for controlling a gain of said dual gate variable gain amplifier;
- a final amplifier stage for further amplifying said input signal;
- and
- means, responsive to said envelope signal, for modulating said final amplifier stage.
A communications device including a power amplifier circuit wherein said power amplifier circuit comprises:
- a driver amplifier stage having an input coupled to an input of said power amplifier circuit, said driver amplifier stage being comprised of a dual gate variable gain amplifier;
- an envelope detector, having an input coupled to said input of said power amplifier circuit, for producing an envelope signal;
- an envelope amplifier coupled to said envelope detector, for producing an amplified envelope signal;
- an analog to digital converter, responsive to said envelope signal, for controlling a gain of said dual gate variable gain amplifier;
- and
- a power amplifier stage having an input coupled to an output of said driver amplifier stage, and having an output coupled to an output of said power amplifier circuit, wherein said power amplifier stage is modulated by said amplified envelope signal.
Dependencies are inferred from the claim text.