Reverse Coupling in Power Amplifiers for SEM-Compliant rIMD Suppression
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Solution Overview
Problem
Mobile communication devices face challenges in suppressing reverse intermodulation products (rIMDs) due to antenna coupling, which can lead to non-compliance with regulatory spurious emissions (SEM) requirements, especially in non-contiguous RF bands like LTE and 5G-NR bands 41, where additional filters are difficult to implement effectively.
Innovation Solution
A power amplifier apparatus with a reverse coupling circuit that generates an interference cancellation signal to suppress rIMDs by amplifying and phase-shifting the signal to match the reverse interference, ensuring compliance with SEM requirements through concurrent transmission and reception in multiple RF spectrums.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional filters are employed to suppress reverse interference signal and rIMDs, then suppression effectiveness is improved, but device complexity and difficulty of implementation increase
Solution Approach 1:
The patent applies preliminary anti-action by generating an interference cancellation signal that is the inverse of the reverse interference signal before it combines with the RF signal in the amplifier. The reverse coupling circuit extracts the reverse interference signal from the antenna port and creates a cancellation signal with opposite phase, which is then combined with the original RF signal to pre-neutralize the harmful rIMDs before amplification, avoiding the need for complex post-amplification filtering
Solution Approach 2:
The patent converts the harmful reverse interference signal into a beneficial cancellation signal. By using the reverse coupling circuit to extract and invert the reverse interference signal, the system transforms the harmful rIMD-generating signal into a useful tool for suppressing itself and similar interference signals, thereby eliminating the need for additional complex filtering components
2Object-affected harmful factors
If power reduction is applied to suppress rIMDs, then SEM compliance is improved, but transmission power and signal quality deteriorate
Solution Approach 1:
The system performs preliminary anti-action by canceling rIMDs at the signal combination stage before amplification. The interference cancellation signal is combined with the RF signal prior to entering the power amplifier, so that when the amplifier boosts the signal, it amplifies both the desired RF signal and the cancellation signal together, achieving SEM compliance without reducing the overall transmission power of the useful signal
Solution Approach 2:
The reverse coupling circuit acts as an intermediary that extracts the reverse interference signal from the antenna port and processes it through phase inversion and recombination. This intermediary mechanism allows the system to selectively cancel only the harmful interference components while preserving and amplifying the useful RF signal, avoiding the need to reduce overall transmission power
3Volume of moving object
If antennas are collocated in close proximity to save space, then device compactness is improved, but reverse interference signal coupling increases
Solution Approach 1:
The patent implements feedback by using the reverse coupling circuit to continuously monitor and extract the reverse interference signal that is coupled back to the antenna port from other transmitting antennas. This extracted signal is then processed and fed back into the signal path as a cancellation signal, creating a closed-loop system that actively compensates for the interference caused by antenna collocation, thereby maintaining compact device design without sacrificing performance
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
The solution effectively suppresses rIMDs to a defined threshold, enabling concurrent LTE and 5G-NR transmissions while meeting stringent SEM requirements without the need for large additional power reduction, thus ensuring reliable and compliant operation in mobile communication devices.
Implementation Method 1
A reverse coupling circuit is provided in the power amplifier apparatus to generate an interference cancellation signal based on the reverse interference signal (e.g., with opposing phase and proportional amplitude relative to the reverse interference signal)
Implementation Method 2
The amplifier circuit is configured to amplify the interference cancellation signal and the RF signal to create an intermodulation product(s) to suppress the rIMD(s) to a determined threshold
Data Source
AI summary
A power amplifier apparatus supporting reverse intermodulation product (rIMD) cancellation is provided. The power amplifier apparatus includes an amplifier circuit configured to amplify and output a radio frequency (RF) signal for transmission via an antenna port. The antenna port may receive a reverse interference signal, which may interfere with the RF signal to create a rIMD(s) that can fall within an RF receive band(s). A reverse coupling circuit is provided in the power amplifier apparatus to generate an interference cancellation signal based on the reverse interference signal. The amplifier circuit is configured to amplify the interference cancellation signal and the RF signal to create an intermodulation product(s) to suppress the rIMD(s) to a determined threshold. By suppressing the rIMD(s) in the power amplifier apparatus, it is possible to support concurrent transmissions and receptions in a number of RF spectrums while in compliance with stringent regulatory spurious emissions (SEM) requirements.