Doherty Amplifier Bias Circuit Miniaturization
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Solution Overview
Problem
Existing Doherty amplifier bias circuits require significant PCB area for separated gate biases, hindering miniaturization and cost reduction, especially in modern mobile equipment and 5G frequencies.
Innovation Solution
A bias circuit with an in-phase N-port dividing impedance transformer and two-port impedance transformer, utilizing micro strip waveguides and physical loads like lumped elements or transmission line stubs, to reduce physical dimensions and PCB area, featuring a Wilkinson or Gysel impedance transformer for efficient bias signal distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separated gate biases are used for isolation in Doherty amplifiers, then isolation between amplifier branches is improved, but PCB area consumption increases significantly
Solution Approach 1:
The patent combines multiple bias signals into a single shared bias line that serves both the carrier and peak amplifiers. Instead of using separate gate bias circuits for each amplifier branch, the invention merges the biasing functions into one common circuit that distributes bias signals to multiple amplifiers, thereby reducing PCB area while maintaining the necessary isolation between branches through adaptive biasing control
Solution Approach 2:
The shared bias line circuit is designed to serve multiple functions: it provides bias signals to both carrier and peak amplifiers, enables adaptive biasing control, and maintains isolation between branches. This multi-functional approach eliminates the need for dedicated separate bias circuits for each amplifier, reducing overall PCB area consumption
2Reliability
If complex biasing circuitry with individual bias stages is used, then amplifier performance is improved, but device complexity and PCB area increase
Solution Approach 1:
The patent merges multiple individual bias stages into a single shared bias line circuit that controls both carrier and peak amplifiers. This consolidation reduces the number of separate biasing components and interconnections, simplifying the overall device complexity while maintaining the performance benefits of adaptive biasing through centralized control
3Adaptability or versatility
If separated bias lines from the bias root are used, then individual amplifier control is improved, but PCB area consumption increases
Solution Approach 1:
The patent merges multiple bias lines into a single shared bias line that distributes bias signals to both carrier and peak amplifiers. This consolidation reduces PCB area consumption by eliminating redundant bias line traces and associated components, while individual amplifier control is maintained through adaptive biasing control that dynamically adjusts the bias signals distributed along the shared line
Data Source
AI summary
A bias circuit for a Doherty amplifier, characterized by comprising: an input port with an input impedance, wherein the input port is configured to receive a bias signal from a power supply; a first output port configured to provide a bias signal to an amplifier; a second output port configured to provide a bias signal to an amplifier; a two port impedance transformer with an input connected to the first input port, and an output of the two port impedance transformer having an intermediate impedance; an in-phase N-port dividing impedance transformer with an input connected to the output of the two port impedance transformer, wherein the in-phase N-port dividing impedance transformer comprises: a first output connected to the first output port having a first output impedance; and a second output connected to the second output port having a second output impedance.