Envelope Tracking Circuit Phase-Shifted Adder Noise Cancellation
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Solution Overview
Problem
Existing power amplifier systems in wireless devices face inefficiencies due to noise in the modulated supply voltage, which affects signal quality and increases power consumption, particularly when up-sampling introduces spurs at image frequencies.
Innovation Solution
A circuit comprising a first and second phase-shifted signal generator and an adder, which up-samples the input stream of envelope values to align the supply voltage modulation with the RF signal, reducing frequency components and noise by adding phase-shifted streams with a 180° difference, thereby canceling image frequency components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If up-sampling is applied to align supply voltage modulation with RF signal, then power consumption is reduced and efficiency is improved, but frequency components and noise are introduced that affect signal quality
Solution Approach 1:
The patent converts the harmful image frequency components introduced by up-sampling into beneficial elements by introducing a phase-shifted version of the up-sampled stream and combining them. The harmful frequency components from the original up-sampling and the harmful frequency components from the phase-shifted up-sampling cancel each other out through destructive interference, while the useful signal components reinforce each other constructively. This transforms the harmful effect of up-sampling into a beneficial noise reduction mechanism.
Solution Approach 2:
The patent applies preliminary anti-action by pre-introducing a phase-shifted version of the envelope signal before the harmful frequency components can degrade the signal quality. By generating the phase-shifted stream in advance and combining it with the original up-sampled stream, the system proactively counteracts the potential harmful effects of image frequency components before they can adversely affect the RF signal quality.
2Object-affected harmful factors
If phase-shifted streams are added to cancel image frequency components, then signal quality is improved, but device complexity increases
Solution Approach 1:
The patent segments the envelope signal processing into two parallel paths: one path processes the original envelope signal while the other path processes a phase-shifted version of the envelope signal. Each path independently generates up-sampled streams, and these segmented processing paths are later combined. This segmentation allows the system to handle the complexity of phase shifting and combination in a modular fashion, making the overall system more manageable and implementable.
Solution Approach 2:
The phase-shifting mechanism serves multiple functions simultaneously: it generates the necessary phase difference for image frequency cancellation, maintains the envelope signal integrity, and enables the constructive interference of useful signal components. This multi-functionality reduces the need for additional separate circuits, thereby limiting the increase in device complexity while achieving signal quality improvement.
3Loss of energy
If supply voltage modulation is applied to power amplifier, then power efficiency is improved, but noise in supply voltage affects signal quality
Solution Approach 1:
The patent introduces an intermediary processing stage for the envelope signal that includes up-sampling and phase-shifted combination before the signal reaches the supply voltage modulation circuit. This intermediary processing cleans up the envelope signal by canceling image frequency components, ensuring that the modulation signal applied to the power amplifier supply voltage is free from harmful frequency components. The intermediary envelope processing acts as a mediator that prevents noise from being transferred to the power amplifier through the supply voltage modulation.
Data Source
AI summary
Aspects of the disclosure provide a circuit that includes a first circuit, a second circuit, and an adder. The first circuit is configured to generate a first signal by outputting and holding, at a first timing, a first stream in response to an input stream of data. The second circuit is configured to generate a second signal by outputting and holding, at a second timing, a second stream in response to the input stream of data. The adder is configured to add the first signal with the second signal to generate an up-sampled stream for the input stream of data and reduce a frequency component in the up-sampled stream generated by the up-sampling.