Doherty Amplifier Bias Coupling for Wideband Linearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Doherty amplifiers face challenges in maintaining linearity, especially with the increasing demands of wider channel bandwidths and higher power requirements in wireless communication systems like 5G and sub-6, where power amplifiers need improved efficiency and linearity.
Innovation Solution
The Doherty amplifier incorporates a carrier amplification transistor, a peaking amplification transistor, and linearization circuits that adjust the coupling of input RF signals based on power modes, using variable resistors and capacitors to enhance linearity by compensating for base voltage drops in transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the channel bandwidth is increased to meet 5G and sub-6 requirements, then the data transmission capacity is improved, but the linearity of the power amplifier deteriorates
Solution Approach 1:
The power amplifier is divided into two separate amplification paths: a carrier amplification transistor for the main signal and a peaking amplification transistor for the peak signals. This segmentation allows each transistor to operate in its optimal region, with the carrier transistor maintaining linearity for continuous signals and the peaking transistor handling high-power peaks, thereby preserving overall linearity while supporting wider bandwidth operation.
Solution Approach 2:
The patent implements dynamic biasing control where the peaking bias voltage is adjusted based on the input signal power level. A bias control circuit dynamically modifies the peaking transistor's bias voltage to maintain optimal operating conditions across varying signal levels, ensuring linearity is preserved during both high-power and low-power transmission modes in wide bandwidth channels.
2Power
If the power class is increased to power class 2 for high power requirements, then the transmission power is improved, but the linearity of the power amplifier deteriorates
Solution Approach 1:
The amplification function is segmented between two transistors operating at different power levels. The carrier amplification transistor handles the continuous low-power signal with high linearity, while the peaking amplification transistor handles high-power peak signals. This segmentation enables the system to achieve power class 2 output while maintaining linearity through coordinated operation of both devices.
Solution Approach 2:
The patent employs dynamic parameter changes by adjusting the bias voltage of the peaking transistor based on signal conditions. The peaking bias circuit changes the operating parameters of the peaking transistor to optimize its performance across different power levels, allowing the amplifier to maintain linearity while delivering high power output when needed.
3Use of energy by moving object
If the efficiency of power amplifiers is improved using Doherty architecture, then the energy efficiency is improved, but the linearity deteriorates
Solution Approach 1:
The Doherty amplifier architecture segments the amplification task between a carrier transistor operating in Class AB for high efficiency and a peaking transistor operating in Class C for peak power handling. This segmentation enables the system to achieve high energy efficiency across the full power range while maintaining linearity through the coordinated operation of both transistors and their respective bias circuits.
Solution Approach 2:
The patent implements feedback control through bias circuits that monitor and adjust the operating points of both transistors. The carrier bias circuit and peaking bias circuit provide feedback control to maintain optimal operating conditions, ensuring that linearity is preserved while maximizing energy efficiency through the Doherty architecture's inherent power-dependent operation.
Data Source
AI summary
A Doherty amplifier includes a carrier amplification transistor configured to amplify a first input radio frequency (RF) signal, a carrier bias circuit configured to supply a carrier bias voltage to the carrier amplification transistor, a peaking amplification transistor configured to amplify a second input RF signal, a peaking bias circuit configured to supply a peaking bias voltage to the peaking amplification transistor, and a first linearization circuit connected between a first terminal to which the second input RF signal is input and a second terminal to which the peaking bias voltage is output in the peaking bias circuit, and configured to couple a portion of the second input RF signal and provide the coupled portion to the second terminal.