Remote Antenna Digital Predistortion for RF Amplifier Linearity
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Solution Overview
Problem
Conventional high-power amplifiers in RF systems are inefficient due to non-linear components causing distortion, leading to increased power consumption and heat dissipation, and are often bulky due to large heat sinks.
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 opposite to the distortion introduced by the power amplifier, with a feedback loop to adjust coefficients and cancel out distortion, thereby improving efficiency and reducing hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional high-power amplifiers are used to amplify RF signals, then the signal power is increased, but distortion is introduced due to non-linear components
Solution Approach 1:
The patent applies pre-distortion to the digital signal before it reaches the power amplifier. The pre-distortion engine modifies the signal in advance with opposite distortion characteristics, so that when the power amplifier introduces its non-linear distortion, the two effects cancel each other out, resulting in a linear overall system response
Solution Approach 2:
The system incorporates a feedback loop where the output of the power amplifier is monitored and fed back to the coefficient computation engine. This feedback is used to continuously update and optimize the pre-distortion coefficients, ensuring that the distortion cancellation remains effective under varying operating conditions
2Object-generated harmful factors
If pre-distortion processing is performed in real-time, then distortion cancellation is achieved, but computational complexity increases
Solution Approach 1:
The pre-distortion function is segmented into two separate units: the radio unit containing the coefficient computation engine for calculating pre-distortion coefficients, and the antenna unit containing the pre-distortion engine for applying the distortion cancellation. This segmentation distributes computational complexity across different locations in the system
Solution Approach 2:
The coefficient computation engine calculates pre-distortion coefficients in advance based on feedback from the power amplifier output, rather than performing complex real-time calculations during signal transmission. This preliminary computation reduces the computational burden during critical real-time operation
Data Source
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Figure 2
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.