Digital Predistortion in Remote Antenna Units for PA Linearity
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Solution Overview
Problem
Current High Power Amplifiers (HPAs) in RF systems are power-consuming, heavy, and large, causing inefficiencies and heat dissipation issues due to non-linear components that introduce distortion, which conventional systems attempt to mitigate by using larger amplifiers operated at lower levels, leading to inefficiencies and heat management challenges.
Innovation Solution
A radio system with a digital pre-distortion engine in the antenna unit and a coefficient computation engine in the radio unit, where the signal is pre-distorted before amplification to counteract the distortion introduced by the power amplifier, using a feedback loop to adjust coefficients and improve signal accuracy, thereby reducing the need for large, inefficient amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional High Power Amplifiers are used to amplify signals, then signal transmission capability is improved, but power consumption, weight, and size increase
Solution Approach 1:
The patent applies pre-distortion to the signal before amplification. The digital pre-distortion engine modifies the signal characteristics in advance to compensate for the non-linear distortion that will be introduced by the power amplifier, allowing the amplifier to operate more efficiently without requiring excessive power consumption or oversized components
2Power
If conventional High Power Amplifiers are used to amplify signals, then signal transmission capability is improved, but weight and size increase
Solution Approach 1:
By pre-distorting the signal digitally before amplification, the system compensates for amplifier non-linearities without requiring larger, heavier amplifier components. The pre-distortion engine calculates and applies correction coefficients that allow the amplifier to achieve desired output performance with reduced weight
3Use of energy by moving object
If power amplifiers operate at higher levels to improve efficiency, then power consumption is reduced, but distortion increases
Solution Approach 1:
The patent implements preliminary anti-action by applying pre-distortion to the signal before amplification. The digital pre-distortion engine introduces opposite distortion characteristics that cancel out the non-linear distortion generated by the power amplifier, allowing the amplifier to operate at efficient power levels while maintaining signal integrity
Solution Approach 2:
The system uses a feedback loop where the output of the power amplifier is monitored and fed back to the coefficient computation engine. This feedback mechanism allows real-time adjustment of pre-distortion coefficients to compensate for changes in amplifier characteristics, maintaining low distortion while operating at high efficiency
4Measurement precision
If digital pre-distortion is applied to cancel amplifier distortion, then signal accuracy is improved, but system complexity increases
Solution Approach 1:
The patent introduces a digital pre-distortion engine as an intermediary component between the signal source and the power amplifier. This intermediary applies mathematical pre-distortion using computed coefficients, improving signal accuracy while keeping the overall system complexity manageable through modular architecture and efficient algorithms
Data Source
AI summary
The radio system comprises a radio unit and an antenna unit coupled to the radio unit. The antenna unit is physically separate and located remote from the radio unit. The antenna unit further comprises a digital pre-distortion engine configured to pre-distort a modulated digital data signal; a digital to analog converter configured to convert the pre-distorted digital data signal to a pre-distorted analog data signal; and a power amplifier configured to amplify the pre-distorted analog data signal which distorts the pre-distorted analog data signal. The distortion introduced by the power amplifier is opposite to the pre-distortion introduced by the digital pre-distortion engine such that the pre-distortion introduced by the digital pre-distortion engine approximately cancels the distortion introduced by the power amplifier. The radio unit further comprises a coefficient computation engine configured to calculate coefficients used by the digital pre-distortion engine to pre-distort the modulated digital data signal.