Load-Adaptive Power Amplifier Biasing for Stable Linearity
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Solution Overview
Problem
Existing signal amplification systems in wireless communication face challenges in maintaining linearity and efficiency due to variations in load impedance, leading to degraded adjacent channel leakage ratio (ACLR) and error vector magnitude (EVM).
Innovation Solution
A load adaptive bias (LAB) circuit is used to monitor the output voltage swings of a main power amplifier (PA) and a replica PA, adjusting the bias of the main PA to match the gain profile of the replica PA, thereby reducing gain variations and improving linearity and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier is used to amplify transmit signals, then signal strength is improved, but linearity and efficiency are degraded due to load impedance variations
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage swing of the power amplifier is sensed and fed back to the biasing circuit. The biasing circuit adjusts the bias voltage based on the sensed output voltage swing to maintain constant gain and improve linearity under varying load impedance conditions.
Solution Approach 2:
The patent dynamically changes the bias voltage parameter of the power amplifier based on the sensed output voltage swing. By adjusting the bias voltage in response to load impedance variations, the amplifier maintains optimal linearity and efficiency across different operating conditions.
2Power
If a power amplifier is used to amplify transmit signals, then signal strength is improved, but efficiency is degraded due to load impedance variations
Solution Approach 1:
The biasing circuit uses feedback from the sensed output voltage swing to dynamically adjust the bias voltage, optimizing the amplifier's efficiency by adapting to load impedance variations in real-time.
Solution Approach 2:
The patent transforms the static bias voltage into a dynamic parameter that adjusts automatically in response to load impedance changes. This dynamic adaptation allows the amplifier to maintain high efficiency across varying operating conditions.
3Adaptability or versatility
If load impedance varies, then adaptability is improved, but gain stability and linearity are degraded
Solution Approach 1:
The feedback mechanism senses the output voltage swing that reflects load impedance variations and adjusts the bias voltage accordingly, maintaining stable gain despite changes in load conditions.
Solution Approach 2:
The amplifier system performs self-adjustment through the biasing circuit that automatically compensates for load impedance variations by sensing the output voltage swing and modifying the bias voltage without external intervention.
Data Source
AI summary
Certain aspects of the present disclosure provide an amplification system. The amplification system generally includes: a first amplifier having an output coupled to an output of the amplification system; a second amplifier, inputs of the first amplifier and the second amplifier being coupled to an input of the amplification system; an impedance coupled to an output of the second amplifier; and a biasing circuit having a first voltage sense input coupled to the output of the first amplifier, a second voltage sense input coupled to the output of the second amplifier, and an output coupled to a bias input of the first amplifier.