Quantized Linear Amplification Using Constant-Envelope Components
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Solution Overview
Problem
Modern communication systems face inefficiencies in power amplification due to high peak-to-average power ratio (PAPR) in signals, leading to nonlinear distortion, inter-carrier interference, and reduced power efficiency, especially in multicarrier modulations like OFDM, which affects spectral and power efficiency in high bit rate communications.
Innovation Solution
The apparatus employs quantization of time domain samples to decompose signals into constant envelope components, which are then amplified by nonlinear amplifiers, avoiding nonlinear distortion and allowing for linear amplification of signals with variant envelopes, independent of the dynamic range of the time domain samples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If high power amplifiers are used to meet power requirements in high bit rate communication systems, then power efficiency is improved, but nonlinear distortion and inter-carrier interference increase due to high PAPR signals
Solution Approach 1:
The signal is decomposed into multiple constant envelope components (CE components) through a decomposition unit. Each CE component can be amplified independently by separate power amplifiers operating in saturated mode, avoiding nonlinear distortion while maintaining high power efficiency. The original signal s(t) is segmented into N components where each component has constant envelope characteristics.
Solution Approach 2:
A pre-distortion unit is introduced as an intermediary component that processes the input signal before decomposition. This unit applies a predetermined nonlinearity to the signal, which compensates for the nonlinear characteristics of the power amplifiers. The pre-distortion transformation prepares the signal in a form that, when passed through the nonlinear amplifiers, produces a linear output signal.
2Object-generated harmful factors
If input power back-off is increased to reduce nonlinear distortions, then nonlinear distortion is reduced, but power efficiency decreases
Solution Approach 1:
Instead of reducing input power to avoid nonlinear distortion, the signal is segmented into multiple constant envelope components. Each component is amplified by a separate amplifier operating at full power (saturated mode), eliminating the need for power back-off while avoiding nonlinear distortion through the constant envelope property of each component.
Solution Approach 2:
The invention changes the envelope parameter of the signal from variable (high PAPR) to constant envelope for each component. By transforming the signal representation into a sum of constant envelope components, the system can operate amplifiers at maximum efficiency without suffering from nonlinear distortion that would occur with high PAPR signals.
3Use of energy by moving object
If quantization of time domain samples is performed to decompose signals into constant envelope components, then power amplification efficiency is improved, but quantization error is introduced
Solution Approach 1:
The quantization process transforms the continuous amplitude values of the signal into discrete constant envelope levels. This parameter change from continuous to discrete values introduces quantization error, but enables the use of highly efficient nonlinear amplifiers. The quantized components are then amplified without nonlinear distortion, and the overall system achieves better power efficiency despite the quantization loss.
Data Source
AI summary
An apparatus for quantized linear amplification with nonlinear amplifiers that performs a linear amplification of variable-envelope single carrier (SC) or multi-carrier (MC) bandpass signals, based on sampled and quantized versions of its complex envelope, where the quantizer generates N b bits that are mapped into N m < N b polar components, in which the quantized symbol can be decomposed, that are modulated as N m constant or quasi constant envelope signals and where each one is amplified by a nonlinear amplifier.