RF Power Amplifier Input Circuit for IM3 Distortion Mitigation
Find Innovative SolutionsGenerate Solutions
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 the fidelity of transmitted signals.
Innovation Solution
Incorporating a second-order intermodulation generation circuit that injects second-order intermodulation signals into the radio-frequency power amplifier to mix with input signals, generating corresponding products that cancel out third-order intermodulation tones, thereby improving the linearity of the amplifier 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 that will cancel the third-order intermodulation distortion products before they degrade the transmitted signal. The circuit generates these canceling signals proactively through a dedicated second-order intermodulation generation circuit that mixes input signals to create second-order products, which are then combined with the main RF signal to pre-compensate for the non-linear distortion that will occur during power amplification.
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 that, when combined with the amplifier's inherent third-order distortion, produce canceling effects. The harmful non-linearity is transformed into a useful mechanism where the second-order products serve as precursors to generate third-order canceling signals, turning the amplifier's defect into a feature for distortion mitigation.
2Manufacturing precision
If linearity of the power amplifier is improved to reduce intermodulation distortion, then signal fidelity is improved, but amplification efficiency deteriorates
Solution Approach 1:
The patent introduces an intermediary second-order intermodulation generation circuit that acts as a mediator between the input signal and the power amplifier. This intermediary circuit generates second-order signals that serve as a bridge to cancel the third-order distortion products, allowing the amplifier to operate in a more efficient non-linear region while still achieving high signal fidelity through the distortion canceling mechanism.
3Object-generated harmful factors
If a second-order intermodulation generation circuit is added to cancel third-order distortion, then intermodulation distortion is reduced, but circuit complexity increases
Solution Approach 1:
The patent merges the second-order intermodulation generation function with the existing power amplifier circuitry by coupling the generation circuit to the input transformer and combining its output with the main RF signal path. This integration approach consolidates multiple functions (signal amplification, second-order signal generation, and distortion canceling) into a unified circuit architecture, reducing overall complexity compared to separate independent systems.
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 across a wide range of output power levels, enhancing the linearity of the radio-frequency power amplifier while maintaining efficiency.
Implementation Method 1
an input transformer configured to receive a radio-frequency signal and coupled to the gate terminals of the first and second input transistors
Implementation Method 2
The second order intermodulation generation circuit can be configured to generate second order intermodulation signals that are used to generate third order intermodulation cancelling signals that cancel or reduce the third order intermodulation products
Data Source
Figure 1
Figure 2
Figure 3
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.