Memory Digital Pre-Distorter Coefficient Initialization for Power Amplifier Calibration
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Solution Overview
Problem
Conventional power amplifiers (PAs) in wireless communication systems experience spectral inefficiencies and non-linearity across varying input amplitude levels, leading to transmit error vector magnitude (TX-EVM) and spectral mask deviations, which can result in decreased signal strength and interference with adjacent channels, making it difficult to maintain compliance with FCC regulations.
Innovation Solution
An electronic device is configured to apply updated memory digital pre-distorter (mDPD) coefficient values to pre-distort the PA input, using a processor and memory to preload, transmit, and update these coefficients based on a training signal sequence, thereby improving PA output characteristics across a wide range of input levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional PAs are used to increase transmission power, then signal strength improves, but spectral inefficiencies and non-linearity increase causing TX-EVM and spectral mask deviations
Solution Approach 1:
The system applies pre-distortion to the input signal before it reaches the power amplifier. By inverting the expected non-linear distortion characteristics in advance, the PA's actual output distortion is counteracted, achieving linearized output that complies with spectral mask requirements while maintaining high transmission power
Solution Approach 2:
The system dynamically adjusts mDPD coefficient values based on operating conditions such as temperature, supply voltage, and input signal characteristics. These parameter changes enable the pre-distorter to adapt to PA non-linearity variations, maintaining spectral mask compliance across different power levels and environmental conditions
2Reliability
If full calibration is performed to improve PA linearity, then TX-EVM and spectral mask compliance improve, but calibration time increases
Solution Approach 1:
The system performs an initial comprehensive calibration to determine mDPD coefficient values, which are then stored in memory for reuse. This preliminary action eliminates the need for repeated full calibrations, reducing calibration time while maintaining PA linearity through the use of pre-determined coefficients
Solution Approach 2:
The system implements a dynamic calibration approach where the extent of recalibration is adapted based on changes in operating conditions. Instead of performing full calibration every time, the system selectively updates coefficients only when necessary, optimizing the trade-off between linearity maintenance and calibration time
3Productivity
If mDPD coefficients are updated frequently to maintain PA characteristics, then spectral efficiency improves, but processing overhead and calibration time increase
Solution Approach 1:
The system performs mDPD coefficient updates at periodic intervals or based on trigger events such as significant temperature changes or supply voltage variations. This periodic update strategy maintains spectral efficiency by keeping coefficients current while minimizing the frequency of calibration operations to reduce processing overhead
Data Source
AI summary
An electronic device configured to apply, to a first power amplifier (PA) input, one or more updated memory digital pre-distorter (mDPD) coefficient values is provided. The electronic device includes a processor; and a memory including a non-transitory computer readable storage medium storing instructions that, when executed, cause the processor to preload, from values stored in the memory of the electronic device, one or more mDPD coefficient values; transmit a training signal sequence while using the preloaded one or more mDPD coefficient values; receive the training signal sequence; update the one or more mDPD coefficient values based on the transmitted training signal sequence, the received training signal sequence, and the preloaded one or more mDPD coefficient values; and apply the updated one or more mDPD coefficient values to distort the first PA input.