Active Antenna Array Predistortion with Common Feedback
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Solution Overview
Problem
The increasing demand for mobile communications systems requires more radio stations, leading to higher maintenance costs and complexity due to nonlinearities introduced by amplifiers in active antenna arrays, which distort payload signals and necessitate individual predistortion for each transmit path.
Innovation Solution
A digital predistortion module with a common feedback path and digital predistortion update module is used to impose a single digital predistortion on all transmit paths, correcting nonlinearities and simplifying maintenance by updating the predistortion based on feedback from a combined signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If individual predistortion units are used for each transmit path, then signal quality is improved by correcting nonlinearities, but device complexity and hardware costs increase
Solution Approach 1:
The patent combines multiple individual predistortion units into a single shared predistortion unit that serves all transmit paths. The feedback signals from multiple transmit paths are combined and fed into one predistortion unit, which then applies correction to all paths, reducing hardware complexity while maintaining signal quality correction capabilities
Solution Approach 2:
The single predistortion unit is designed to handle multiple transmit paths simultaneously, making it a universal component that performs the function of what would traditionally require multiple separate units. This multi-functional approach reduces the overall number of components needed in the system
2Adaptability or versatility
If more radio stations are deployed to meet increasing demand, then service coverage is improved, but maintenance costs and complexity increase
Solution Approach 1:
The patent merges multiple transmit paths into a single radio station with shared components including the predistortion unit, amplifiers, and feedback paths. This consolidation allows one radio station to provide service coverage that would traditionally require multiple separate stations, thereby reducing the number of sites that need maintenance
3Power
If amplifiers are used to amplify transmit signals, then transmission power is improved, but nonlinearities are introduced that distort payload signals
Solution Approach 1:
The predistortion unit applies preliminary correction to the transmit signal before it reaches the amplifier. By pre-distorting the signal in the opposite direction of the expected amplifier nonlinearity, the system counteracts the harmful effects before they occur, allowing the amplifier to operate at high power while maintaining signal integrity
Solution Approach 2:
The patent implements feedback paths that capture the output from each transmit path and feed it back to the predistortion unit. This feedback mechanism allows the system to continuously monitor and adjust the predistortion parameters to compensate for amplifier nonlinearities, ensuring accurate signal transmission despite high power amplification
Data Source
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AI summary
The present disclosure relates to a radio station (1) providing a digital predistortion (24) to be imposed on a payload signal (15). The digital predistortion (24) is usable as a general predistortion for several transmit paths (70-1, ..., 70-N) of the radio station (1). The radio station (1) provides coupled transmit signals (80-1, ..., 80-N) to be combined within a combiner (100) forming a common feedback signal (155). The common feedback signal (155) is relayed along a common feedback path (150). A digital predistortion update unit (22) is adapted to update the digital predistortion (24) in order to linearise a transfer characteristics of the transmit paths (70-1, ..., 70-N). The disclosure further relates to a method of digitally predistorting a payload signal (15) in order to linearise a transmit characteristics of the transmit paths (70-1, ..., 70-N).