Orthogonal Load Modulation Amplifier With Autonomous RF Attenuation Control
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Solution Overview
Problem
Existing load modulation amplifiers require external phase or amplitude control signals and dual RF input signals, limiting their application in achieving high continuous power backed off (PBO) efficiency.
Innovation Solution
A single RF input and output power amplifier implementation using an input splitter, analog power detector, and variable attenuator to autonomously generate control signals, eliminating the need for external phase or amplitude control, and achieving high PBO efficiency through an orthogonal load modulation amplifier (OLMPA) with a quadrature coupler and splitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If external phase or amplitude control signals are used in load modulation amplifiers, then the amplifier can achieve load modulation capability, but the device complexity and power consumption increase due to additional control signal requirements
Solution Approach 1:
The amplifier uses its own output signal to generate the control signal through an envelope detector, eliminating the need for external control signals. The envelope detector extracts the amplitude information from the output signal, which then controls the attenuator to achieve load modulation automatically
Solution Approach 2:
The system implements feedback by detecting the envelope of the output signal and using it to control the attenuator. The envelope detector monitors the output signal characteristics and feeds this information back to adjust the attenuation, creating a closed-loop control system that achieves load modulation without external inputs
2Loss of energy
If dual RF input signals are used in load modulation amplifiers, then the amplifier can achieve high PBO efficiency, but the ease of operation deteriorates due to requiring two synchronized input signals
Solution Approach 1:
The amplifier processes a single RF input signal and uses its own output to generate the control signal needed for load modulation. The envelope detector extracts control information from the amplifier's own output, eliminating the need for a second input signal while maintaining high efficiency operation
Solution Approach 2:
The single RF input signal serves multiple functions: it is both the carrier signal and the source for generating the envelope control signal. The system achieves both amplification and load modulation control from a single input, making the amplifier more versatile and easier to operate
3Ease of operation
If a simplified load modulation amplifier is used that requires no external control signal, then the ease of operation improves, but the device complexity increases due to additional active amplifiers and feedforward RF paths
Solution Approach 1:
The control function is extracted from the main signal path and implemented separately using an envelope detector. This allows the amplifier to achieve autonomous operation without adding complexity to the core amplification path, as the control signal generation is handled by a dedicated detection circuit
Solution Approach 2:
The envelope detector acts as an intermediary that converts the output signal into a control signal without requiring additional active amplifiers in the main path. This mediator component enables autonomous operation by bridging the output and control input through a passive detection mechanism
Data Source
AI summary
A load modulation amplifier is disclosed having a first amplifier and a second amplifier. An input quadrature coupler and an output quadrature coupler are coupled between the first amplifier and the second amplifier. A splitter has a first splitter output, a splitter input coupled to a signal input, and a second splitter output coupled to a second port of the input quadrature coupler, and a variable attenuator is coupled between the first splitter output and a first port of the input quadrature coupler. An attenuation controller has a controller output that is coupled to an attenuation control input of the variable attenuator, wherein the attenuation controller autonomously generates a control signal in response to a power sample signal in proportion to a radio frequency signal received at the radio frequency signal input.