Digital Baseband IMD Compensation in Direct Sampling Receivers
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Solution Overview
Problem
Existing non-linearity compensation techniques in wireless base station receivers struggle to effectively handle intermodulation distortion (IMD) and harmonic distortion simultaneously, leading to unpredictable frequency generation and complex mathematical models required for accurate analysis.
Innovation Solution
A digital non-linearity compensation scheme is implemented in the digital baseband of a direct sampling basestation receiver, focusing solely on intermodulated non-linearity content. This approach generates a corrective term using a preset non-linearity coefficient and a third-order multiplication of in-phase and quadrature data, without compensating for harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If digital non-linearity compensation is implemented in the RF band, then linearity performance is improved, but power consumption increases significantly
Solution Approach 1:
The patent transitions the non-linearity compensation from the RF domain to the baseband domain, changing the dimensional space where compensation occurs. This dimensionality change allows using lower sampling rates and simpler digital processing while maintaining compensation effectiveness, thereby reducing power consumption significantly
2Reliability
If both harmonic distortion and intermodulation distortion are compensated simultaneously, then comprehensive distortion reduction is achieved, but system complexity increases
Solution Approach 1:
The patent extracts and addresses only the intermodulation distortion component from the mixed distortion signal, separating it from harmonic distortion. By focusing on compensating only IMD in the baseband, the system achieves practical distortion reduction without the excessive complexity of simultaneously handling both distortion types
Solution Approach 2:
The patent segments the distortion compensation task by separating intermodulation distortion from harmonic distortion, and further segments the processing by applying compensation only in the baseband domain rather than across the entire signal processing chain, making the system more manageable and less complex
3Measurement precision
If high-sampling rate RF ADC is used, then frequency response accuracy is improved, but power consumption increases
Solution Approach 1:
The patent moves the critical measurement and compensation operations from the RF domain to the baseband domain, where lower sampling rates suffice. This dimensional transition maintains frequency response accuracy for the bands of interest while dramatically reducing the sampling rate requirements and associated power consumption
Solution Approach 2:
The patent applies local quality by focusing compensation resources on the specific baseband frequency components that matter for the application, rather than uniformly processing the entire RF spectrum. This localized approach in the baseband domain achieves necessary accuracy with reduced power consumption
Data Source
AI summary
In some implementations, the circuitry may include a circuit configured to receive a baseband signal, the baseband signal having an intermodulated non-linear distorted portion and a harmonic distorted portion. In addition, the circuitry may include a compensator coupled to the circuit, the compensator configured to generate a value to compensate for the intermodulated non-linear distorted portion without compensating for the harmonic distorted portion. The circuitry may include where the compensator is configured to output the value. The circuitry may include where the circuit is configured to adjust the baseband signal using the value. In some embodiments, the baseband signal can be baseband voltage. In some embodiments, the value can be a complex number.