RF Front End Linearity Control Under VSWR Mismatch
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Solution Overview
Problem
Mobile device front end modules experience performance degradation due to degraded linearity, especially in envelope tracking (ET) mode with high modulation bandwidth, caused by mismatch at the antenna and memory effects from duplexers, which traditional digital pre-distortion (DPD) methods fail to adequately address.
Innovation Solution
A power amplifier system that includes a modulator, a front end module with a power amplifier, a coupler, and a processor that adjusts the RF transmit signal based on voltage standing wave ratio (VSWR) measurements using an equalizer table to compensate for memory effects and mismatch, incorporating a programmable antenna tuner for impedance tuning and fine correction of non-linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional digital pre-distortion (DPD) methods are used to compensate for power amplifier non-linearity, then some linearity improvement is achieved, but memory effects and mismatch-induced degradation (especially under ET mode with high modulation bandwidth) are not adequately addressed
Solution Approach 1:
The patent implements dynamic adaptation of DPD parameters based on real-time detection of operating conditions (modulation bandwidth, ET mode status, mismatch levels). The system continuously adjusts pre-distortion coefficients and memory effect compensation parameters to match current operating conditions, transforming the static DPD approach into a dynamic system that maintains optimal linearity across varying conditions.
Solution Approach 2:
The patent changes multiple parameters simultaneously including modulation bandwidth detection, ET mode detection, and mismatch detection to adapt the DPD compensation strategy. By monitoring these parameters and adjusting the pre-distortion algorithm accordingly, the system addresses memory effects and mismatch-induced degradation that traditional fixed DPD cannot handle.
2Productivity
If the system operates in envelope tracking (ET) mode with high modulation bandwidth to improve power efficiency and data rate, then power efficiency and throughput are improved, but linearity degradation becomes progressively worse due to memory effects and mismatch
Solution Approach 1:
The patent incorporates feedback mechanisms that detect operating conditions (modulation bandwidth, ET mode, mismatch) and use this information to adaptively adjust the DPD parameters. The system measures actual performance degradation and feeds this information back to modify the pre-distortion compensation, creating a closed-loop system that maintains linearity even under high modulation bandwidth ET mode operation.
Solution Approach 2:
The patent applies preliminary pre-distortion compensation based on detected operating conditions before the signal passes through the power amplifier. By detecting ET mode and high modulation bandwidth conditions in advance, the system pre-adjusts the DPD parameters to compensate for the specific memory effects and non-linearities that will occur under these conditions, preventing rather than correcting the degradation.
3Measurement precision
If dual directional coupler is used to monitor forward and reverse power for VSWR measurement, then mismatch detection capability is improved, but device complexity increases
Solution Approach 1:
The patent makes the dual directional coupler serve multiple functions: it monitors forward power for output power control, monitors reverse power for VSWR/mismatch detection, and provides feedback for adaptive DPD adjustment. By making this single component multi-functional, the system achieves precise measurement capabilities without proportionally increasing overall device complexity.
Data Source
AI summary
A power amplifier system front end measures both forward and reverse power associated with an RF transmit signal. A processor is configured to use measurements derived from the measured forward and reverse power output to adjust the RF transmit signal in order to compensate for one or more memory effects of the power amplifier system.