Multi-Band Predistortion Linearizer with Single Subsampling Feedback
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Solution Overview
Problem
Multi-band transmitter systems face challenges in linearizing nonlinear behavior, particularly with intermodulation, cross modulation, and harmonic products, which degrade signal quality, and existing digital predistortion techniques require complex feedback loops and multiple RF components, increasing power consumption and complexity.
Innovation Solution
A concurrent digital multi-band linearizer using a baseband signal preprocessing block with a digital predistortion unit, signal up-conversion, and an RF power amplification block, along with an RF power combining network, employs a single feedback loop with subsampling receivers to down-convert multiple frequency bands simultaneously, simplifying the system and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple RF components and multi-band down conversion units are used in the feedback loop, then the signal quality and linearization performance are improved, but the power consumption and system complexity increase
Solution Approach 1:
The patent combines multiple down conversion functions into a single subsampling receiver that can simultaneously process multiple frequency bands. Instead of using separate RF components for each band, the invention merges them into one unified feedback loop that subsamples the combined multi-band signal, thereby reducing system complexity while maintaining linearization performance
Solution Approach 2:
The subsampling receiver is designed as a universal component that can handle multiple frequency bands simultaneously. This single receiver performs the function of what would traditionally require multiple band-specific receivers, reducing both the number of components and overall system complexity while maintaining the ability to compensate for nonlinearities across all bands
2Reliability
If multiple RF components and multi-band down conversion units are used in the feedback loop, then the linearization performance is improved, but the power consumption increases
Solution Approach 1:
By merging multiple down conversion paths into a single subsampling receiver, the patent eliminates redundant RF components and their associated power consumption. The unified feedback loop processes all frequency bands through one receiver chain, significantly reducing the total power required compared to having separate receivers for each band
Solution Approach 2:
The universal subsampling receiver performs multiple functions simultaneously - it down-converts and processes signals from multiple frequency bands in parallel, replacing what would traditionally require multiple power-consuming RF components. This multi-functional approach maintains linearization performance while minimizing power consumption
3Device complexity
If subsampling technique is used to simplify the feedback loop, then the system complexity and power consumption are reduced, but the performance may be insufficient in the presence of uncontrolled interfering signals
Solution Approach 1:
The patent employs a feedback mechanism where the subsampled signal is used to generate predistortion coefficients that are applied to the input signal. This feedback loop continuously adapts to compensate for nonlinearities and intermodulation products, ensuring that signal quality is maintained even with the simplified subsampling architecture
Solution Approach 2:
The invention carefully selects and optimizes the subsampling frequency parameter to avoid aliasing of intermodulation products into the signal bands. By changing the sampling frequency parameter to specific values that satisfy certain mathematical relationships with the carrier frequencies, the system maintains signal quality while using the simplified subsampling approach
4Reliability
If digital predistortion is applied to compensate for nonlinearities, then the signal quality is improved, but the system complexity increases due to multiple processing blocks
Solution Approach 1:
The patent merges the digital predistortion processing for multiple frequency bands into a single unified processing block. Instead of having separate predistortion processors for each band, the invention combines them into one block that processes all bands simultaneously using the subsampled feedback signal, thereby reducing processing complexity while maintaining signal quality
Data Source
AI summary
A concurrent multi-band linearized transmitter (CMLT) has a concurrent d a 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.