Doherty Amplifier Neutralization Circuitry for Distortion Reduction
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Solution Overview
Problem
Doherty RF amplifiers generate undesirable distortion when the peaking amplifier becomes active, due to parasitic feedback signals.
Innovation Solution
Incorporation of neutralization circuitry that injects signals 180°±10% out of phase and equal in amplitude to parasitic feedback signals, using neutralization amplifiers to cancel out these signals, thereby reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the peaking amplifier is activated to increase output power, then the amplifier can operate at higher power levels, but distortion increases due to parasitic feedback signals
Solution Approach 1:
The patent converts the harmful parasitic feedback signals into beneficial neutralization signals by injecting inverted versions of these signals through the neutralization circuitry. The parasitic feedback capacitances that cause distortion are utilized to generate the neutralization signals, which are then injected 180 degrees out of phase to cancel the harmful effects, thereby eliminating distortion while maintaining high power operation
Solution Approach 2:
The neutralization circuitry acts as an intermediary between the parasitic feedback paths and the amplifier inputs. It captures the parasitic feedback signals through dedicated capacitances, inverts their phase, and injects them back into the amplifier inputs to cancel the harmful feedback, thereby mediating between the power amplification function and the distortion problem
2Object-generated harmful factors
If neutralization circuitry is added to reduce distortion, then distortion is reduced, but device complexity increases
Solution Approach 1:
The patent merges the neutralization function with the existing amplifier structure by integrating the neutralization circuitry into the feedback paths. The main neutralization circuitry is coupled between the main amplifier output and input, and the peak neutralization circuitry is coupled between the peaking amplifier output and input, combining multiple functions into unified circuit blocks that reduce overall complexity
Solution Approach 2:
The neutralization system is segmented into two independent but coordinated subsystems: main neutralization circuitry for the main amplifier and peak neutralization circuitry for the peaking amplifier. Each subsystem handles its respective amplifier's parasitic feedback independently, allowing modular design and simplifying the overall implementation while effectively addressing distortion across the full power range
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The neutralization circuitry effectively eliminates parasitic feedback signals, reducing distortion and improving the overall performance of the Doherty amplifier.
Implementation Method 1
the main neutralization circuitry is configured to generate a main neutralization signal that is 180°±10% out of phase and equal in amplitude to within ±10% of a main parasitic feedback signal
Implementation Method 2
the peak neutralization circuitry is configured to generate a peak neutralization signal that is 180°±10% out of phase and equal to within ±10% in amplitude to a peak parasitic feedback signal
Data Source
AI summary
A Doherty amplifier is disclosed with a main amplifier having a main input in communication with a radio frequency (RF) signal input and a main output in communication with a RF signal output. Also included is a peaking amplifier having a peak input in communication with the RF signal input and a peak output in communication with the RF signal input. Further included is main neutralization circuitry having a main neutralization input in communication with the peak input and a main neutralization output in communication with the main input, wherein the main neutralization circuitry is configured to inject a main neutralization signal into the main input such that the main neutralization signal is 180°±10% out of phase and equal in amplitude to within ±10% of a main parasitic feedback signal passed from the main output to the main input by way of a main parasitic feedback capacitance.