Multi-Band RF Predistortion After Upconversion for PA Linearity
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Solution Overview
Problem
Conventional digital predistortion techniques are not optimal for multi-band transmitters, as they face challenges in managing non-linear signal distortion and require high sampling rates and complex digital upconversion processes, especially when dealing with wideband signals like CDMA and OFDM.
Innovation Solution
Implementing Radio Frequency Digital Predistortion (RF-DPD) systems that digitally predistort RF signals after upconversion, reducing sampling rates and eliminating the need for additional upconversion paths to handle inter-band distortion products, while allowing for explicit synthesis of intra-band and inter-band distortion products for each band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If baseband digital predistortion is used to compensate for PA non-linearity, then linearity is improved, but sampling rate requirements and computational complexity increase significantly for multi-band signals
Solution Approach 1:
The patent segments the multi-band signal processing into separate band-specific predistortion paths. Each band is processed independently through its own digital upconversion and predistortion chain, avoiding the need to process all inter-band distortion products in a single baseband path. This segmentation reduces the sampling rate requirements and computational complexity while maintaining linearity compensation for each band.
2Reliability
If baseband digital predistortion is used for multi-band signals, then non-linear distortion is compensated, but additional digital upconversion paths are required for inter-band distortion products
Solution Approach 1:
The patent inverts the conventional approach by performing digital upconversion first and then applying predistortion at the RF stage. Instead of generating all distortion products at baseband and then upconverting them, the system upconverts each band separately and applies predistortion after upconversion, eliminating the need for additional upconversion paths for inter-band distortion products.
3Use of energy by moving object
If PA operates close to saturation to maximize power efficiency, then power efficiency is improved, but non-linear signal distortion increases
Solution Approach 1:
The patent applies preliminary predistortion to the signal before it enters the power amplifier. By pre-compensating the signal with inverse non-linear characteristics in the digital domain and after digital upconversion, the system enables the PA to operate close to saturation for maximum power efficiency while the predistortion prevents significant non-linear distortion in the final output signal.
Data Source
AI summary
Systems and methods for radio frequency digital predistortion in a multi-band transmitter are disclosed. In one embodiment, the multi-band transmitter includes a digital upconversion system configured to digitally upconvert digital input signals to provide digital radio frequency signals. Each digital input signal and thus each digital radio frequency signal corresponds to a different band of a multi-band transmit signal to be transmitted by the multi-band transmitter. The multi-band transmitter also includes a radio frequency digital predistortion system configured to digitally predistort the digital radio frequency signals to provide predistorted digital radio frequency signals, and a combiner configured to combine the predistorted digital radio frequency signals to provide a multi-band predistorted digital radio frequency signal.