Asymmetric Multilevel Outphasing RF Amplifiers for Combiner Loss Recovery
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Solution Overview
Problem
Conventional RF transmitter architectures face challenges in achieving both high linearity and efficiency, particularly for high data-rate communication standards like WiMAX, due to inefficiencies in power amplifiers and power combiners, leading to wasted energy and signal distortion.
Innovation Solution
The asymmetric multilevel outphasing (AMO) transmitter architecture and modulation control method utilize a switch network and power supply to generate multiple voltages for power amplifiers, allowing for efficient power combining and minimizing energy loss through optimized voltage selection and phase adjustment, thereby enhancing efficiency and reducing signal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional LINC architecture with isolating combiner is used, then amplifier efficiency is preserved, but power is wasted as heat in the combiner resistor when inputs are outphased to vary amplitude
Solution Approach 1:
The patent recovers the power that would otherwise be wasted as heat in the combiner resistor by using a power recovery network that captures the outphased signals and converts them back to DC power, which is then returned to the power supply. This transforms the harmful energy dissipation into useful energy recovery, directly addressing the contradiction between preserving amplifier efficiency and reducing power waste.
Solution Approach 2:
The patent converts the harmful effect of power being wasted as heat in the isolating combiner into a beneficial outcome by using power recovery networks that capture these outphased signals and convert them back to useful DC power. The previously wasted energy becomes a recoverable resource that improves overall system efficiency.
2Loss of energy
If polar architecture is used to improve power amplifier efficiency, then efficiency increases, but a high-bandwidth power converter is required which degrades converter efficiency
Solution Approach 1:
The patent extracts and eliminates the high-bandwidth power converter from the system by using outphasing architecture combined with power recovery networks. Instead of modulating the power supply voltage with high bandwidth as in polar architecture, the invention separates the amplitude and phase control functions, removing the need for the problematic high-bandwidth converter while maintaining power amplifier efficiency.
Solution Approach 2:
The patent replaces the high-bandwidth voltage modulation mechanism of polar architecture with a switching-based outphasing approach. Instead of continuously varying the power supply voltage with high bandwidth, the system uses switching mode power amplifiers with recovered power feedback, substituting a simpler switching mechanism for the complex high-bandwidth voltage control system.
3Productivity
If variable-envelope modulation is used for high data rates, then data rate increases, but linear amplification is required which reduces efficiency
Solution Approach 1:
The patent segments the amplitude and phase control functions by using multiple switching mode power amplifiers that operate in parallel with outphased signals. Each amplifier handles a simplified signal with constant envelope, allowing efficient switching mode operation, while the combined output through the power recovery network achieves the variable-envelope modulation needed for high data rates.
Solution Approach 2:
The patent introduces dynamic power recovery and redistribution mechanisms that adapt to the instantaneous signal conditions. The power recovery networks dynamically capture and return power based on the outphasing angles and signal amplitudes, enabling the system to maintain high efficiency across varying signal conditions while supporting variable-envelope modulation for high data rates.
Data Source
Figure 1
Figure 1A~1B
Figure 1C
AI summary
A radio frequency (RF) circuit includes a power supply configured to generate a plurality of voltages, a plurality of power amplifiers, each having an RF output port and a power supply input port, a switch network having a plurality of input ports coupled to the power supply and a plurality of switch network output ports coupled to the power supply input ports of the plurality of power amplifiers, wherein the switch network is configured to output selected ones of the plurality of voltages from the plurality of switch network output ports, at least two of the switch network output port voltages capable of being different ones of the plurality of voltages, and an RF power combiner circuit having a plurality of input ports coupled to RF output ports of the plurality of power amplifiers and an output port at which is provided an output signal of the RF circuit.