Multi-Band RF Amplifier Feedback Routing for Low-Delay Linearization
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Solution Overview
Problem
In wireless RF networks, existing solutions for managing signals across multiple frequency bands face challenges in linearization and gain control, particularly due to the non-linear characteristics of power amplifiers and the introduction of significant group delay, which affects the performance of digital predistortion systems.
Innovation Solution
The implementation of a radio apparatus with multiple amplifiers for different frequency bands, utilizing digital predistorters with complementary half-band filters and a common feedback path to route and linearize signals, along with gain controllers to adjust and stabilize the power levels, minimizes the effects of group delay and non-linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If digital predistortion systems are used to linearize power amplifier signals, then linearity is improved, but significant group delay is introduced which degrades system performance
Solution Approach 1:
The patent divides the predistortion processing into separate parallel paths for different frequency bands (e.g., first predistorter for first band, second predistorter for second band). Each predistorter processes only its designated band, avoiding the cumulative group delay that would result from sequential processing of all bands through a single predistortion system. This segmentation allows independent optimization of each band's linearity while minimizing overall group delay.
Solution Approach 2:
The patent employs periodic switching between different frequency bands using a switch that alternates between connecting the first band signal and the second band signal to the common feedback path. This periodic action allows the system to process different bands in alternating time intervals, reducing the impact of group delay by ensuring that feedback is obtained for each band during its active period rather than being delayed by processing of other bands.
2Adaptability or versatility
If multiple amplifiers are used to cover different frequency bands, then frequency coverage is improved, but device complexity increases
Solution Approach 1:
The patent combines multiple frequency band processing paths into a single common feedback path that is shared by all amplifiers. Instead of providing separate feedback paths for each frequency band, the system merges the feedback signals and uses a single feedback loop for linearization control. This merging approach maintains the ability to cover multiple frequency bands while significantly reducing the overall system complexity by eliminating redundant feedback infrastructure.
Solution Approach 2:
The common feedback path serves multiple functions: it provides feedback for linearization of the first frequency band, feedback for linearization of the second frequency band, and enables gain control for multiple bands. The switch enables this single feedback path to be universally used across different frequency bands by routing the appropriate band's output signal to the feedback path during each time interval, making the feedback system multi-functional rather than requiring dedicated feedback paths for each band.
3Device complexity
If a common feedback path is used for multiple amplifiers, then device complexity is reduced, but signal interference between bands may increase
Solution Approach 1:
The switch implements periodic action by alternately connecting the output of the first amplifier and the output of the second amplifier to the common feedback path in non-overlapping time intervals. During each interval, only one amplifier's output is present on the feedback path, eliminating the possibility of signal interference between bands. This time-division approach ensures that feedback signals for different bands are obtained separately without mutual contamination, preventing inter-band interference while still using a shared feedback infrastructure.
Solution Approach 2:
The switch performs preliminary action by pre-routing the appropriate amplifier output to the feedback path before feedback processing occurs. By ensuring that only the currently active band's signal is present on the feedback path at any given time, the system prevents potential interference from other bands before it can occur. This preliminary routing action guarantees that the feedback signal contains only the intended band's information, maintaining signal integrity across multiple bands.
Data Source
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AI summary
An apparatus is disclosed, comprising means for providing two or more amplifiers (122, 124) for amplifying signals in two or more respective frequency bands, receiving a composite signal comprising first and second predistorted input signals in first and second frequency bands and filtering the composite signal to provide the first predistorted signal for input to a first amplifier (122) of the two or more amplifiers (122, 124) for producing an amplified first output signal and the second predistorted signal for input to a second amplifier (124) of the two or more amplifiers (122, 124) for producing an amplified second output signal. The apparatus may also comprise means for routing (146), at non-overlapping times, the first and second output signals to a common feedback path and for linearizing received first and second input signals based on the respective first and second output signals received on the common feedback path.