Nonlinear Envelope Bandwidth Compression for Wideband RF Linearity
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Solution Overview
Problem
Envelope tracking systems in mobile communication devices face limitations in maintaining linearity and efficiency due to bandwidth constraints, particularly with the advent of 5G-NR technology, which requires higher bandwidth modulation, leading to signal distortion and spectral degradation.
Innovation Solution
The implementation of nonlinear bandwidth compression circuitry within the envelope tracking system, which modifies predefined voltage waveforms to generate modified waveforms that are never less than the original, allowing for bandwidth compression without degrading spectral performance, and corrects signal distortions through digital pre-distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If envelope tracking system operates with higher bandwidth modulation to support 5G-NR technology, then data rates and user experience are improved, but linearity and efficiency deteriorate due to exceeding inherent bandwidth limit
Solution Approach 1:
The system performs preliminary bandwidth compression on the voltage waveform before it reaches the power amplifier. By pre-compressing the voltage envelope bandwidth to match the PA's optimal operating range, the system enables wideband RF signals to be amplified with maintained linearity and efficiency. The compression is done in advance, allowing the PA to operate within its bandwidth capabilities while still supporting wideband modulation.
Solution Approach 2:
The invention changes the bandwidth parameter of the voltage waveform by applying nonlinear compression. The voltage envelope is transformed from a wideband signal to a compressed-bandwidth signal that fits within the power amplifier's optimal operating bandwidth. This parameter transformation allows the system to support wideband RF modulation while keeping the voltage control signal within narrower bandwidth limits.
2Quantity of substance
If envelope tracking system operates with higher bandwidth modulation, then signal capacity is improved, but spectral performance deteriorates due to signal distortion
Solution Approach 1:
The system applies preliminary nonlinear bandwidth compression to the voltage waveform before amplification. This pre-compression ensures that the voltage envelope variations remain within the bandwidth capabilities of the power amplifier, preventing the generation of spectral regrowth and adjacent channel interference that would otherwise occur with wideband voltage modulation.
3Power
If power amplifier output power is increased to achieve higher data rates, then communication performance is improved, but power consumption and thermal dissipation increase
Solution Approach 1:
The envelope tracking system continuously monitors the instantaneous power requirements of the RF signal and dynamically adjusts the supply voltage to the power amplifier in real-time. By providing feedback control, the system ensures the PA operates at optimal efficiency across varying power levels, reducing overall power consumption and thermal dissipation compared to fixed-voltage operation.
Data Source
AI summary
Nonlinear bandwidth compression circuitry is provided. In examples discussed herein, nonlinear bandwidth compression circuitry can be configured to modify predefined amplitude(s) of a predefined voltage waveform to generate modified amplitude(s) of a modified voltage waveform that is never less than the predefined amplitude(s) of the predefined voltage waveform. Thus, by providing the nonlinear bandwidth compression circuitry in an envelope tracking (ET) system to perform bandwidth compression, signal distortion(s) resulted from the bandwidth compression can be corrected (e.g., via digital pre-distortion). As such, the ET system can amplify a radio frequency (RF) signal having a signal modulation bandwidth exceeding a voltage modulation bandwidth limitation of the ET system, without degrading spectral performance of the RF signal.