Feedforward Amplifier Linearizer for Wideband Linearity Control
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Solution Overview
Problem
Existing amplification circuits in wireless communication networks face challenges in achieving high bandwidth and linearity, particularly in power amplifiers used for standards like 5G new radio, which require wide bandwidths and high linearity while maintaining efficiency and minimizing distortions.
Innovation Solution
The proposed amplification circuit includes a feedforward path with a low-impedance path coupled to a feedforward node, a biasing circuit, and a resistive device, which dynamically adjusts the bias current to compensate for non-linearity and memory effects, allowing operation across a wide bandwidth and improving signal amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional amplification circuit is used, then the circuit can amplify signals, but the bandwidth is limited and linearity is poor
Solution Approach 1:
The amplification circuit is divided into multiple independent paths: a main amplification path and a feedforward path. Each path processes the signal separately, with the feedforward path specifically designed to compensate for non-linearities. This segmentation allows independent optimization of linearity (through feedback control) and bandwidth (through parallel signal paths), resolving the contradiction between these two parameters.
Solution Approach 2:
A feedforward path is implemented that feeds a portion of the input signal forward to compensate for non-linear distortions. This feedback mechanism dynamically adjusts the amplification characteristics, improving linearity while the feedforward architecture itself maintains wide bandwidth by providing additional signal paths that operate in parallel with the main amplification path.
2Adaptability or versatility
If the bandwidth is increased to support wide frequency ranges, then the circuit can operate across multiple standards, but linearity and signal quality deteriorate
Solution Approach 1:
The circuit uses parallel amplification paths where each path can be optimized for different frequency ranges. The feedforward path specifically targets and corrects non-linear distortions across the entire bandwidth, allowing the main path to operate at high gain while maintaining linearity through the corrective action of the segmented feedforward path.
Solution Approach 2:
The circuit dynamically adjusts bias conditions and signal routing based on operating frequency and signal characteristics. By changing parameters such as bias current and path selection, the circuit maintains optimal linearity across wide bandwidth variations, adapting to different frequency ranges while preserving signal quality.
3Loss of energy
If power amplification is increased to improve efficiency, then energy consumption is reduced, but non-linearity and distortions increase
Solution Approach 1:
The feedforward path continuously monitors and compensates for non-linear distortions generated by high-power amplification. By feeding forward a corrected version of the input signal, the system can operate the main power amplifier at high efficiency levels while the feedback path cancels out the resulting non-linearities, maintaining signal linearity even at high power levels.
Solution Approach 2:
The amplification system combines multiple amplification mechanisms in parallel: a high-efficiency power amplification path and a linearity-compensation path. This composite approach allows the system to leverage the efficiency benefits of high-power operation while simultaneously applying correction mechanisms that restore linearity, achieving both high efficiency and high linearity concurrently.
Data Source
AI summary
Certain aspects of the present disclosure provide methods and apparatus for amplifying signals with an amplification circuit. The amplification circuit generally includes a first transistor, an input path coupled between an input node of the amplification circuit and a control input of the first transistor, and a feedforward path coupled between the input node and a feedforward node. In certain aspects, the amplification circuit may also include a first resistive device coupled between the feedforward node and the control input of the first transistor, a biasing circuit coupled to the feedforward node, and a low-impedance path coupled to the feedforward node.