Receiver Chain Impedance Measurement for Stable Non-Linearity Compensation
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Solution Overview
Problem
Wideband receivers, particularly in 5G/sub-6G base station applications, face unpredictable non-linearity distortion due to varying source impedances, leading to insufficient harmonic distortion cancellation and reduced spurious free dynamic range (SFDR) performance.
Innovation Solution
A non-linearity compensation method that performs measurements on specific nodes of the receiver chain to obtain impedance-dependent results, using either an impedance-based or distortion transfer function (DTF)-based approach to calculate and subtract harmonic distortion estimates from the processed signal, thereby mitigating source-dependent distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If non-linearity cancellation (NLC) technique is implemented to achieve high SFDR performance, then spurious free dynamic range is improved, but source-dependent distortion makes the NLC outcome unpredictable and can worsen baseline distortion
Solution Approach 1:
The patent measures the actual source impedance presented to the receiver front-end and uses this measured parameter to dynamically adjust and optimize the non-linearity cancellation coefficients. This transforms the fixed, unpredictable NLC approach into an adaptive system that accounts for varying source impedance conditions, thereby maintaining reliable and predictable distortion cancellation across different installation scenarios.
Solution Approach 2:
The patent introduces a feedback mechanism where the receiver measures its own source impedance and uses this information to adjust the NLC parameters. This closed-loop approach ensures that the NLC system adapts to the actual operating conditions, making the outcome predictable and reliable rather than dependent on idealized assumptions about source impedance.
2Ease of manufacture
If distortion model is constructed in production testing with assumed source impedance, then non-linearity compensation can be applied, but distortion variation due to different source impedages in customer systems renders the model ineffective
Solution Approach 1:
The patent performs source impedance measurement and distortion characterization during production testing, storing the measured parameters for later use. This preliminary action captures the actual source impedance conditions present in the customer system, ensuring that the distortion model is built on real-world data rather than theoretical assumptions, thereby maintaining model effectiveness across different installations.
Solution Approach 2:
The patent uses measured source impedance parameters obtained during production testing to customize the distortion model for each specific receiver unit. By incorporating actual measurement data into the model construction process, the system adapts to the unique electrical characteristics of each installation, ensuring the distortion model remains applicable and effective in the customer's actual system environment.
3Adaptability or versatility
If different transmission line lengths are routed on PCB, then system flexibility is improved, but different source impedances are seen by on-chip RX AFE causing distortion variation
Solution Approach 1:
The receiver system automatically measures its own source impedance conditions and adjusts its non-linearity cancellation parameters accordingly, without requiring external calibration or manual intervention. This self-service approach ensures that distortion consistency is maintained regardless of the transmission line configuration, as the system adapts to its own electrical environment.
Solution Approach 2:
The patent dynamically adjusts the NLC parameters based on the measured source impedance, which varies with transmission line length and configuration. By changing the compensation parameters to match the actual electrical conditions, the system maintains consistent distortion performance across different PCB layouts and transmission line lengths, eliminating the need for separate calibration procedures.
Data Source
AI summary
A non-linearity compensation method includes: performing measurement to obtain at least one measurement result for at least one first node of a receiver (RX) chain, wherein the at least one measurement result is source impedance dependent; and performing non-linearity compensation upon a processed signal generated by the RX chain, wherein the non-linearity compensation is based at least partly on the at least one measurement result.