Power Amplifier Bias Switching for Linearity Across Output Modes

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Solution Overview

Problem

Existing power amplifiers face challenges in maintaining linearity across both high and low output modes, with constant voltage sources leading to increased gain and reduced linearity in low output modes, and constant current sources causing decreased gain and linearity issues in high output modes.

Innovation Solution

A power amplification module that includes an amplification circuit, a biasing circuit, a constant voltage generation circuit, a constant current generation circuit, and a switching unit controlled by a control unit to switch between these circuits based on output mode, using constant voltage for high output modes and constant current for low output modes to maintain linearity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a constant voltage source is used for the biasing circuit in low output mode, then the power amplifier can operate with high output power, but gain increases as output power increases and linearity cannot be maintained

Engineering Contradiction:

Improveoutput powerVSAvoidlinearity

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent applies dynamics by making the biasing circuit adjustable between constant voltage and constant current modes based on the output power level. The control unit dynamically switches the biasing mode: constant voltage mode for high output power and constant current mode for low output power, allowing the system to adapt its characteristics to maintain linearity across different operating conditions

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the electrical parameters of the biasing circuit by switching between constant voltage and constant current sources. This parameter change allows the power amplifier to maintain optimal linearity characteristics: constant current biasing for low output mode prevents gain increase, while constant voltage biasing enables high output power operation

Inventive Principle:

Principle #35Parameter changes

2Reliability

If a constant current source is used for the biasing circuit in high output mode, then the power amplifier can operate with low output power, but gain decreases as output power increases and linearity in vicinity of saturation cannot be maintained

Engineering Contradiction:

Improvelinearity at low outputVSAvoidoutput power

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The system dynamically switches the biasing mode based on the required output power level. When high output power is needed, the control unit switches to constant voltage biasing mode, which allows the power amplifier to maintain linearity in the vicinity of saturation output power. When low output power is sufficient, it switches to constant current biasing mode to maintain linearity at low output levels

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the biasing circuit parameters from constant current to constant voltage when operating in high output mode. This parameter change enables the power amplifier to deliver high output power while maintaining linearity characteristics in the saturation region, overcoming the limitation of constant current biasing

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If a single biasing mode is used for all output power levels, then the circuit structure is simple, but linearity cannot be maintained across both high and low output modes

Engineering Contradiction:

Improvebiasing circuit structureVSAvoidlinearity across output modes

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent implements multi-functionality by making the biasing circuit capable of operating in two distinct modes: constant voltage mode and constant current mode. The control unit selects the appropriate mode based on the output power requirements, allowing a single biasing circuit to serve multiple functions and maintain linearity across different operating conditions without requiring separate circuits for each mode

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The biasing circuit is made dynamic by introducing a control unit that switches between constant voltage and constant current biasing modes. This dynamic adaptation allows the circuit to maintain linearity across both high and low output modes, resolving the contradiction between circuit simplicity and linearity performance

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10804861B2Power amplification module, method for controlling power amplification module, and high-frequency front end circuit

Publication Date: 2020.10.13 MURATA MFG CO LTD

AI summary

A power amplification module includes an amplification circuit, a biasing circuit, a constant voltage generation circuit, a constant current generation circuit, a switching unit, and a control unit for controlling a switching operation of the switching unit, and the control unit causes the switching unit to perform switching to connect the constant voltage generation circuit to an input end of the biasing circuit when an output mode is a first output mode in which a high-frequency signal having no less than a predetermined output power is outputted from the amplification circuit, and causes the switching unit to perform switching to connect the constant current generation circuit to the input end of the biasing circuit when the output mode is a second output mode in which a power less than the predetermined output power is outputted from the amplification circuit.