Multi-Band Predistortion Linearizer for Nonlinear Subsampling Feedback
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Solution Overview
Problem
Multi-band digital predistortion linearization faces challenges in efficiently compensating for nonlinearities and intermodulation distortions in RF power amplifiers, particularly in selecting appropriate sampling frequencies to avoid overlap between desired and undesired signal products in subsampling receivers.
Innovation Solution
A concurrent digital multi-band linearizer architecture using a baseband signal preprocessing block, digital predistortion unit, signal up-conversion, and RF power amplification with a subsampling receiver feedback loop, employing multiple RF down-conversion units and an iterative algorithm to determine optimal sampling frequencies for subsampling, ensuring no overlap between desired and undesired signal products.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If subsampling receiver architecture is used in the feedback loop, then power consumption and system complexity are reduced, but selecting appropriate sampling frequency becomes complex to avoid signal overlap
Solution Approach 1:
The patent changes the sampling frequency parameter dynamically based on the specific multi-band signal configuration. By calculating and selecting optimal sampling frequencies that satisfy the non-overlapping condition for each set of band frequencies, the system adapts the sampling parameter to avoid signal overlap while maintaining the power-efficient subsampling architecture.
Solution Approach 2:
The patent implements a feedback mechanism where the sampling frequency selection is based on the actual band frequencies being transmitted. The system monitors the frequency bands and adjusts the sampling frequency accordingly to prevent overlap between desired signals and intermodulation products, creating a closed-loop control for optimal performance.
2Reliability
If multiple processing blocks are employed for multi-band linearization, then distortion compensation is improved, but system complexity increases
Solution Approach 1:
The patent merges multiple processing functions into a unified digital predistortion processing block. Instead of implementing separate processing blocks for each frequency band, the system combines the linearization processing for multiple bands within a single integrated block, reducing system complexity while maintaining comprehensive distortion compensation across all bands.
Solution Approach 2:
The patent creates a universal processing block that handles multiple frequency bands simultaneously. The digital predistortion unit is designed to process signals across different bands using a unified approach, making the processing block multi-functional and eliminating the need for separate dedicated blocks for each band.
3Loss of energy
If RF power amplifier operates in high efficiency region, then power efficiency is improved, but nonlinear behavior introduces unwanted intermodulation distortions
Solution Approach 1:
The patent applies preliminary action by pre-distorting the input signal before it reaches the power amplifier. The digital predistortion unit modifies the input signal in advance to compensate for the expected nonlinear behavior of the amplifier, so that when the signal passes through the high-efficiency amplifier, the distortions are already corrected, maintaining both power efficiency and signal quality.
Solution Approach 2:
The patent implements preliminary anti-action by introducing a reverse model of the amplifier's nonlinear behavior into the predistortion processing. This creates an opposing distortion that cancels out the harmful intermodulation products generated by the amplifier, effectively neutralizing the harmful factors before they degrade the output signal quality.
Data Source
AI summary
A concurrent multi-band linearized transmitter (CMLT) has a concurrent digital multi-band predistortion block (CDMPB) and a concurrent multi-band transmitter (CMT) connected to the CDMPB. The CDMPB can have a plurality of digital baseband signal predistorter blocks (DBSPBs), an analyzing and modeling (A&M) stage, and a signal observation feedback loop. Each DBSPB can have a plurality of inputs, each corresponding to a single frequency band of the multi-band input signal, and its output corresponding to a single frequency band; each output connect corresponding to an input of the CMLT. The A&M stage can have a plurality of outputs connected to and updating the parameters of the DBSPBs, and a plurality of inputs connected to either both outputs of the signal observation loop or the output of the subsampling loop and to outputs of the DBSPBs. The A&M stage can perform signals' time alignment, reconstruction of signals and compute parameters of DBSPBs.