Direct RF Sampling in MIMO DPD Calibration Chains
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Solution Overview
Problem
Current digital pre-distortion calibration methods for MIMO transceivers require large circuit footprints and increased costs due to the inclusion of components like mixers, subtractors, and filters for downconverting signals, which also introduce insertion loss and complicate the calibration process.
Innovation Solution
Implementing direct sampling in the MIMO transceiver's DPD calibration chain, where signals are sampled at a baseband frequency based on a sampling rate lower than the signal frequency, eliminating the need for downconverting components and reducing the circuit footprint, and using a DPD circuit to calibrate pre-distortion parameters based on the sampled signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If downconverting components (mixers, subtractors, filters) are included in the DPD calibration chain, then signal downconversion capability is improved, but circuit footprint and cost increase
Solution Approach 1:
The patent removes the downconverting components (mixers, subtractors, filters) from the DPD calibration chain, extracting only the essential sampling function. This eliminates the need for complex downconversion while maintaining the ability to capture signal characteristics for pre-distortion calibration.
Solution Approach 2:
The patent replaces the mechanical/electronic downconversion system with a direct sampling approach using a data converter. Instead of using mixers and filters to downconvert signals, the system directly samples the RF signal at a reduced rate to obtain baseband-equivalent information for DPD calibration.
2Adaptability or versatility
If downconverting components are included in the DPD calibration chain, then signal processing capability is improved, but insertion loss increases
Solution Approach 1:
The patent extracts only the essential measurement function from the downconversion chain, removing the components that contribute to insertion loss. By using direct sampling, the system avoids the signal path through mixers and filters that would introduce additional loss.
3Adaptability or versatility
If downconverting components are included in the DPD calibration chain, then signal downconversion is improved, but calibration process complexity increases
Solution Approach 1:
The patent extracts only the essential sampling function from the complex downconversion process, removing mixers, subtractors, and filters. This simplifies the calibration chain to a single data converter that directly samples the signal, reducing both hardware complexity and calibration process complexity.
Solution Approach 2:
The patent creates a simplified copy of the downconversion function through direct sampling. Instead of physically downconverting the signal through multiple stages, the system captures the essential signal characteristics directly at the sampling point, achieving the same calibration objective with fewer components.
Data Source
AI summary
A MIMO transceiver may include a communication chain configured to generate a signal at a first frequency. The communication chain may include a pre-distorter configured to accept pre-distortion parameters to pre-distort signals. The communication chain may include a PA to amplify the signals. The MIMO transceiver may include a DPD chain configured to receive the signal at the first frequency. The DPD chain may include a data converter to sample the signal using a sampling rate based on a baseband frequency. The data converter may be configured to generate a sample signal based on the sampling of the signal. The DPD chain may include a buffer configured to buffer the sample signal. The MIMO transceiver may include a DPD circuit configured to calibrate the pre-distortion parameters calibrated based on the buffered sample signal to compensate for non-linearity in amplification provided by the PA of the communication chain.