Doherty Power Amplifier Output Circuit With Integrated Coupler Filter
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Solution Overview
Problem
Traditional Doherty power amplifier circuits face challenges in reducing size, improving linear properties, and enhancing efficiency due to the space occupation and differential loss caused by couplers and filters, leading to increased PCB size and cost.
Innovation Solution
The implementation of a rheostat filter formed by four microstrip lines with different sizes and impedances, which serves as a combination output circuit to perform impedance conversion and harmonic restraint, effectively reducing the size and differential loss while maintaining high reliability and low cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coupler and filter are provided at the combination output end of the Doherty power amplifier circuit, then the DPD training function and harmonic restraint function are implemented, but the size of the microstrip line and PCB size increase
Solution Approach 1:
The patent combines the coupler and filter functions into a single integrated structure at the combination output end. The microstrip lines are configured to simultaneously provide both the coupling needed for DPD training and the filtering needed for harmonic restraint, eliminating the need for separate components and reducing overall PCB space.
Solution Approach 2:
The microstrip line structure is designed to perform multiple functions: impedance matching, signal coupling for DPD training, and harmonic filtering. This multi-functional design replaces what would traditionally require separate components, thereby reducing the total area occupied on the PCB.
2Reliability
If a coupler and filter are provided at the combination output end of the Doherty power amplifier circuit, then the DPD training function and harmonic restraint function are implemented, but the differential loss increases and efficiency decreases
Solution Approach 1:
By merging the coupler and filter into a single integrated microstrip structure, the patent reduces the total length of transmission lines and the number of connection points. This minimizes signal reflections and impedance mismatches, thereby reducing differential loss and improving overall efficiency.
3Reliability
If traditional impedance conversion line and separate filter components are used, then impedance matching and harmonic restraint are achieved, but the device complexity and cost increase
Solution Approach 1:
The patent integrates multiple functions (impedance conversion, coupling, and filtering) into a single microstrip line structure with specific characteristic impedances (53Ω, 12Ω, 96Ω, and 23Ω). This eliminates the need for separate impedance conversion lines, couplers, and filters, thereby reducing device complexity and component count.
4Ease of operation
If traditional Doherty power amplifier structure with multiple separate components is used, then the amplifier functions are implemented, but the size and cost of the power amplifier circuit increase
Solution Approach 1:
The patent consolidates multiple separate components (impedance conversion line, coupler, and filter) into a single integrated microstrip structure. This dramatically reduces the space required for the power amplifier circuit while maintaining all necessary functions, making the overall device more compact and cost-effective.
Data Source
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Figure 3~5
AI summary
A Doherty power amplifier circuit is provided, which includes a power divider circuit, and a power amplifier circuit connected with the power divider circuit; this Doherty power amplifier circuit further includes a combination output circuit connected with the power amplifier circuit, wherein the combination output circuit is a rheostat filter coupler, or a rheostat filter, or a rheostat coupler. By adopting the circuit, the size of a power amplifier circuit can be reduced, the cost of the power amplifier circuit can be lowered, and the efficiency of a power amplifier can be improved.