Doherty Power Amplifier Bias Split to Cut Matching Losses
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Solution Overview
Problem
Current RF power amplifiers in wireless communication systems face challenges in reducing power consumption and power loss while maintaining efficiency and RF bandwidth, with the RF power amplifier being a significant power consumer in transmitters.
Innovation Solution
The implementation of a Doherty power amplifier architecture with a low voltage driver stage (e.g., 5V) and a high voltage final stage (e.g., 28-32V) for the carrier amplifier path, and a high voltage driver stage and final stage for the peaking amplifier path, which includes a low-voltage driver stage for the carrier amplifier path and a high-voltage driver stage for the peaking amplifier path, optimizing bias voltages and impedance matching to enhance efficiency and gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a conventional RF power amplifier uses high voltage throughout all stages to maintain gain and efficiency, then the amplifier can deliver sufficient output power, but DC power consumption increases significantly
Solution Approach 1:
The patent applies parameter changes by using different voltage levels for different amplifier stages. Specifically, the driver stage operates at a first voltage level (e.g., 5V) while the final stage operates at a second voltage level (e.g., 28-32V). This allows the system to achieve sufficient output power through the high-voltage final stage while reducing overall DC power consumption by using lower voltage in the driver stage.
Solution Approach 2:
The patent segments the amplifier into distinct stages with different voltage operating conditions. The amplifier is divided into a driver stage and a final stage, each optimized for its specific function and voltage level. This segmentation allows independent optimization of each stage's power efficiency and performance characteristics.
2Power
If impedance matching networks are designed for high voltage operation across all stages, then power transfer is optimized, but losses in the matching networks increase
Solution Approach 1:
The patent changes the operating voltage parameter in the impedance matching networks by providing a first impedance matching network for the driver stage operating at the first voltage level, and a second impedance matching network for the final stage operating at the second voltage level. This allows each matching network to be optimized for its specific voltage level, reducing losses that would occur if a single high-voltage optimized network were used throughout.
3Ease of manufacture
If the amplifier uses uniform voltage biasing across all stages, then the design and manufacturing is simplified, but overall efficiency and gain are compromised
Solution Approach 1:
The patent applies local quality by assigning different voltage biasing conditions to different parts of the amplifier system. The driver stage and its associated components (including the first impedance matching network) operate at the first voltage level, while the final stage and its components operate at the second voltage level. This local differentiation optimizes performance in each region without requiring complete system redesign.
Data Source
AI summary
Doherty power amplifiers and devices are described with a low voltage driver stage in a carrier-path and a high voltage driver stage in a peaking-path. In an embodiment a Doherty power amplifier has a carrier-path driver stage transistor configured to operate using a first bias voltage at the driver stage output, and a final stage transistor configured to operate using a second bias voltage at the final stage output. A peaking-path driver stage transistor is configured to operate using a third bias voltage at the driver stage output, and a final stage transistor electrically coupled to the driver stage output of the peaking-path driver stage transistor is configured to operate using a fourth bias voltage at the final stage output, wherein the third bias voltage is at least twice as large as the first bias voltage.