RF Power Amplifier IMD Cancellation Using Injected Second-Order Signals
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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 the 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, then the transmission power is increased, but third-order intermodulation distortion is generated that degrades signal fidelity
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 amplifier's non-linearity to produce third-order intermodulation products that cancel the distortion components before they can degrade the transmitted signal, thereby maintaining signal fidelity while operating at high power levels
Solution Approach 2:
The patent converts the harmful effect of amplifier non-linearity into a beneficial effect. By deliberately generating second-order intermodulation signals and allowing them to pass through the non-linear amplifier, the system produces third-order intermodulation products that cancel the distortion. The non-linearity, which was originally the source of harm, becomes the mechanism for distortion cancellation
2Loss of energy
If the power amplifier operates at high efficiency, then energy consumption is reduced, but intermodulation distortion increases affecting signal quality
Solution Approach 1:
The patent implements a feedback mechanism where second-order intermodulation signals are generated based on the input signal and then injected back into the amplifier input. This feedback loop continuously provides the cancellation signals needed to counteract intermodulation distortion, allowing the amplifier to operate at high efficiency points while maintaining signal quality through active distortion compensation
3Manufacturing precision
If linearization techniques are applied to reduce intermodulation distortion, then signal fidelity is improved, but amplifier efficiency is degraded
Solution Approach 1:
The patent changes the signal parameters by injecting second-order intermodulation signals at specific amplitudes and phases. By carefully controlling these parameter changes, the system achieves distortion cancellation while allowing the amplifier to operate in a high-efficiency region, avoiding the need for traditional linearization techniques that would compromise efficiency
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.