RF Power Amplifier With Sub-50 Ω Interstage Matching
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Solution Overview
Problem
Radio frequency modules used in small-sized earth stations for satellite communication face size increase due to the need for internal matching circuits and high-cost GaN-MMICs, especially when achieving high output powers in the Ku band.
Innovation Solution
A power amplifier design that conjugately matches transistors and MMICs at impedance smaller than 50 Ω, using input and output matching circuits and drain bias circuit boards to reduce module size and manufacturing costs, while maintaining high output power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If internal matching type FETs are used in multiple stages to achieve high output power, then the output power is improved, but the module size increases due to necessary matching circuits and peripheral circuits
Solution Approach 1:
The patent combines multiple amplifier stages (driver stage and final stage) into a single integrated package, eliminating the need for external matching circuits between stages. The conjugately matched configuration allows direct coupling of the MMIC output to the transistor input, merging what would traditionally be separate components into one compact unit.
Solution Approach 2:
The drain bias circuit board serves multiple functions simultaneously: it provides DC biasing for both the MMIC and transistor, acts as an RF ground reference, and enables thermal management. This multi-functionality reduces the number of separate components needed, thereby reducing overall module size.
2Area of stationary object
If GaN-MMICs are used to reduce module size, then the module size is reduced, but the manufacturing cost increases due to expensive SiC substrates
Solution Approach 1:
The patent applies different technologies to different stages of the amplifier based on cost-performance optimization. The expensive GaN-MMIC is used only in the driver stage where high performance is critical, while the less expensive discrete transistor is used in the final high-power stage, achieving local optimization of the system.
Solution Approach 2:
The patent changes the impedance parameter from the conventional 50 Ω system to a conjugately matched impedance system. This parameter change enables the use of different device types in different stages while maintaining overall system performance, allowing cost optimization through selective component placement.
3Ease of operation
If conventional 50 Ω matching is used between amplifier stages, then impedance matching is simplified, but the module size increases due to necessary matching circuits
Solution Approach 1:
The patent fundamentally changes the impedance parameter from the conventional 50 Ω system to a conjugately matched impedance system. By designing the transistor and MMIC to be conjugately matched at an impedance smaller than 50 Ω, the need for external matching circuits is eliminated while maintaining optimal power transfer and gain.
Data Source
AI summary
A power amplifier according to the present disclosure includes an input terminal that receives a high-frequency signal from an outside, an MMIC that receives the high-frequency signal via the input terminal and amplifies the high-frequency signal, an input matching circuit, a transistor that receives, via the input matching circuit, the high-frequency signal amplified by the MMIC and amplifies the high-frequency signal, an output matching circuit, an output terminal that receives a drain voltage of the transistor from the outside, receives, via the output matching circuit, the high-frequency signal amplified by the transistor, and outputs the high-frequency signal to the outside and a drain bias circuit board that connects a drain of the transistor and a drain of the MMIC, wherein the transistor and the MMIC are conjugately matched at impedance smaller than 50 Ω.