GaN Power Amplifier Bias Circuit for Small Signal Suppression
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Solution Overview
Problem
Gallium nitride high electron mobility transistors (GaN HEMT) used in solid state power amplifiers for satellite communication suffer from small signal suppression due to memory effects and distortion characteristics, particularly affecting the transmission of small signal waves in satellite news gathering and wideband/multilevel modulation communication systems.
Innovation Solution
The power amplification apparatus includes a field effect transistor (FET) with decoupling elements that reduce inductance and impedance in the drain bias circuit, utilizing a shunt capacitor to suppress the envelope component and improve frequency characteristics, thereby reducing small signal suppression by minimizing the memory effect and anti-resonance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If GaN HEMT is used for power amplification, then transmission output power is significantly improved, but small signal suppression occurs due to memory effect of drain or gate bias
Solution Approach 1:
The bias circuit is segmented into multiple independent bias lines (first bias line for gate bias, second bias line for drain bias) with different impedance characteristics. This segmentation allows each bias line to be optimized independently, preventing the memory effect from affecting small signal transmission while maintaining high power output capability.
Solution Approach 2:
Different impedance values are assigned to different bias lines based on their specific functions. The gate bias line has one impedance value optimized for gate control, while the drain bias line has a different impedance value optimized for power output. This local quality differentiation resolves the contradiction between power output and small signal suppression.
2Device complexity
If commonly used bias circuit configuration is used, then device complexity is low, but anti-resonance occurs and frequency characteristics are degraded
Solution Approach 1:
The invention changes the impedance parameter of the bias circuit by introducing multiple bias lines with different impedance values. This parameter change eliminates anti-resonance phenomena and improves frequency characteristics without significantly increasing device complexity, as the added components are integrated into the existing bias circuit structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively decreases small signal suppression, maintaining the integrity of both large and small signal transmission by optimizing the impedance and frequency characteristics of the bias circuit, ensuring reliable communication in satellite and terrestrial digital television broadcasting.
Implementation Method 1
a shunt capacitor to suppress the envelope component
Implementation Method 2
decoupling elements that reduce inductance and impedance in the drain bias circuit
Data Source
AI summary
According to one embodiment, a power amplification apparatus includes an field effect transistor (FET), a first decoupling element, a power supply circuit, a second decoupling element, and a third decoupling element. The FET is arranged within a package having an input terminal and an output terminal, and power-amplify an input signal from the input terminal to a transmission signal. The first decoupling element decreases an inductance component of the transmission signal output from the FET. The power supply circuit supplies a driving power to the FET. The second decoupling element cut an RF component. The third decoupling element decreases an impedance of a drain bias circuit over a wide band.