Broadband Doherty Power Amplifier Without Quarter-Wave Load Transformation
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Solution Overview
Problem
Existing broadband Doherty power amplifiers have narrow operating bandwidths due to quarter-wave impedance transformation lines, which complicates the circuit and fails to meet the high bandwidth requirements of fifth-generation communication technology.
Innovation Solution
A broadband Doherty power amplifier design that removes the quarter-wave impedance transformation line after the combination point by setting the impedance of the power amplifier combination point equal to the system load, using a load modulation network to combine signals from carrier and peak power amplifiers, and employing matching circuits to adjust impedances according to specific formulas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If quarter-wave impedance transformation lines are used in the load modulation network, then the circuit structure is simple, but the operating bandwidth is narrow
Solution Approach 1:
The patent extracts and removes the quarter-wave impedance transformation line from the load modulation network. By setting the impedance of the power amplifier combination point equal to the system load impedance, the impedance transformation function is eliminated, thereby removing the limiting component and achieving broadband operation without sacrificing circuit simplicity
Solution Approach 2:
The patent changes the impedance parameter of the power amplifier combination point to be equal to the system load impedance. This parameter modification eliminates the need for impedance transformation, enabling the circuit to operate across a wide bandwidth while maintaining structural simplicity
2Adaptability or versatility
If equivalent impedance transformer circuits are used to replace quarter-wave lines, then the operating bandwidth is widened, but the circuit complexity increases
Solution Approach 1:
Instead of replacing the quarter-wave line with complex equivalent circuits, the patent extracts and removes the impedance transformation requirement entirely by proper impedance matching at the combination point, achieving broadband operation with simpler circuitry
Solution Approach 2:
The patent inverts the conventional approach by not trying to transform impedance to match the load, but rather designing the combination point impedance to naturally equal the load impedance, thereby eliminating the need for transformation components
Data Source
AI summary
A broadband Doherty power amplifier is provided, which includes a power divider, a carrier power amplifier circuit, a peak power amplifier circuit, and a load modulation network. The carrier power amplifier circuit includes a carrier input matching circuit, a carrier power amplifier, and a carrier output matching circuit. The peak power amplifier circuit includes a peak input matching circuit, a peak power amplifier and a peak output matching circuit. A resistance value of a system load is ZL. An output impedance of the carrier output matching circuit is Zm and meets Zm=ZL(n+1). An output impedance of the peak output matching circuit is Zp and meets Zp=ZL(n+1)/n. The load modulation network is configured to set an impedance of a combination point to be ZQ, whose resistance value is ZL. A method of implementing a broadband Doherty power amplifier is further provided.