RF Power Amplifier Input Circuit for IMD3 Cancellation
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Solution Overview
Problem
Designing a satisfactory radio-frequency power amplifier for electronic devices is challenging due to non-linear behavior, which results in intermodulation distortion, particularly third-order intermodulation distortion, affecting signal fidelity and amplifier efficiency.
Innovation Solution
Incorporating a second-order intermodulation generation circuit that generates and injects second-order intermodulation signals to mix with input signals, canceling out third-order intermodulation products through a radio-frequency power amplifier, thereby improving linearity without degrading efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a radio-frequency power amplifier is designed to amplify signals for long-distance transmission, then transmission power is improved, but third-order intermodulation distortion increases due to non-linear behavior
Solution Approach 1:
The patent applies preliminary anti-action by generating second-order intermodulation signals in advance and injecting them into the amplifier input. These pre-generated signals interact with the non-linear amplifier to produce third-order intermodulation products that cancel out the harmful distortion components, thereby reducing overall third-order intermodulation distortion while maintaining high transmission power
Solution Approach 2:
The patent converts the harmful non-linear behavior of the power amplifier into a beneficial effect. By deliberately generating second-order intermodulation signals and allowing them to pass through the non-linear amplifier, the system creates third-order intermodulation products that are designed to cancel the harmful distortion, thus transforming the amplifier's non-linearity from a problem into a solution
2Manufacturing precision
If a second-order intermodulation generation circuit is added to reduce third-order intermodulation distortion, then signal fidelity is improved, but device complexity increases
Solution Approach 1:
The patent merges the second-order intermodulation generation circuit with the existing power amplifier structure. The generation circuit uses transistors and inductors that are integrated into the amplifier's input stage, sharing common components and signal paths. This consolidation reduces overall device complexity compared to having separate, independent circuits for signal generation and amplification
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 approach effectively reduces third-order intermodulation distortion, enhancing the fidelity of transmitted signals while maintaining the efficiency of the power amplifier.
Implementation Method 1
A power amplifier may exhibit third order non-linearity resulting in third order intermodulation products that can distort the radio-frequency signals during amplification
Implementation Method 2
An input transformer may include a primary inductor having first and second terminals configured to receive the radio-frequency signal and a secondary inductor having a first terminal coupled to the gate terminal of the first input transistor
Data Source
AI summary
An electronic device may include wireless circuitry with a processor, a transceiver, an antenna, and a front-end module coupled between the transceiver and the antenna. The front-end module may include one or more power amplifiers for amplifying a signal for transmission through the antenna. Radio-frequency power amplifier circuitry may include an amplifier, an input transformer for coupling radio-frequency input signals to the amplifier, an active inductor load coupled to the input transformer, and a second order intermodulation generation circuit configured to generate and inject a second order intermodulation product into the input transformer. The injected second order intermodulation product can be used to cancel out unwanted third order intermodulation products generated by the amplifier, which reduces intermodulation distortion experienced by the amplifier circuitry.