Dual-Biased FET RF Amplifier for Lower Intermodulation Distortion
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Solution Overview
Problem
Existing radio frequency (RF) amplifiers in wireless systems face challenges in achieving linear operation without consuming excessive current, degrading noise performance, or sacrificing bias voltage gain controllability, particularly in high-power applications like 5G NR, due to nonlinearities in transconductance amplifiers.
Innovation Solution
A dual-transistor RF amplifier configuration is employed, where two field effect transistors (FETs) are biased with different gate and drain voltages to reduce third-order nonlinear frequency components and transconductance, using an offset gate or drain voltage to minimize intermodulation distortion, maintaining a constant bias during operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single transistor RF amplifier is used to achieve linear operation, then the amplifier can provide sufficient gain, but it consumes excessive current and exhibits high third-order nonlinear frequency components
Solution Approach 1:
The single transistor amplifier is segmented into two parallel transistor branches. Each transistor operates at a lower bias current individually, but their combined output provides the required total current and gain. This segmentation reduces the third-order nonlinear frequency components while maintaining linearity and reducing overall power consumption.
2Reliability
If the gate bias voltage is increased to improve linearity, then the third-order nonlinear frequency components are reduced, but the noise performance degrades
Solution Approach 1:
Different gate bias voltages are applied to different transistors in the parallel configuration. By optimizing the bias voltage for each transistor individually, the circuit achieves reduced third-order nonlinear frequency components while maintaining acceptable noise performance through the combined output of multiple devices operating at optimized local conditions.
3Ease of operation
If a single transistor is used to provide high gain, then the bias voltage gain controllability is maintained, but the third-order transconductance is high causing nonlinear distortion
Solution Approach 1:
The gain function is segmented across two parallel transistor branches. Each transistor contributes partially to the total gain, allowing the overall gain to be controlled through bias voltages while the distributed configuration reduces the third-order transconductance and resulting intermodulation distortion compared to a single high-gain transistor.
Data Source
AI summary
Aspects of this disclosure relate to linearized radio frequency amplifiers. A radio frequency amplifier can include first and second field effect transistors configured to receive a radio frequency input signal and provide first and second intermediate amplified signals, respectively. The first field effect transistor can have a first source and a first gate electrically biased at a first gate bias voltage and the second field effect transistor can have a second source and a second gate electrically biased at a second gate bias voltage different from the first gate bias voltage. The radio frequency amplifier can be configured to generate a combined output signal comprising the first and second intermediate amplified signal,